MPG Fit Physics
New Member
Joined: Jan 2010
Posts: 17
From: above and beyond
asianmoomoo,
my advice will not be surprising and should work for any car. The web has lots of videos and discussions on how to get the best MPG. The physics are to find out how much difference a driving change makes and quantify it, then it is up to you. Example is to use AC or not. We are blessed with a built in, but inaccurate guage, to teach us to drive skillfully. I learned my techniques on a 1995 GTI VR6 (has MPG meter) and was able to cruise at 30 MPG on a good day.
Best MPG:
1) long trips are best to reduce the penalty of warming up. Lots of short trips together are the next best thing. I don't have any data yet how much gas is used to reach operating temperature.
2) maintain a steady speed. acceleration is costly. This can easily be quantified with my models. And don't use the brakes if you can.
3) whenever possible watch the traffic and coast whenever it is safe to do so. Coasting in neutral with engine off is just about free, neutral with engine on nearly free, and coasing in drive least economical. In one future post I intend to show at what incline threshold you fail to get most of your energy back. This requires some math.
4) hills are extremely costly, therefore take it easy, let the car slow down if you can get away with it. Downhill, coast and even let the speed go a little high if safe to do so. My rule is 5 MPH under on the climb and 5 MPH over downhill will avoid tickets and road rage. If the hill is too steep to coast at a safe speed you will waste gas braking but use the energy to run the AC if that is beneficial. I tend to discourage you all from engine off coasting since your power steering will be off and you have only a small reserve of power brake left for the stop. You don't need power steering at speed but if someone cuts you off or a deer jumps out into the road it can be very dangerous. hybrids have aux power for forced auto stop, we don't. Besides, I don't know how much life the puny starter motor has, and the flat towing feature of the AT is probably not good at 75 MPH.
5) turns use more gas. How much depends on the slip angle of the tires where turning force results in parasitic drag. Hard cornering will increase rolling resistance. However I have used "scrubbing off speed" to drive route 20 from Corvallis to Newport with minimal braking on turns. It is fun and will outrun most drivers. Don't do this is you are not skilled at it! Oregon doesn't have guard rails on many roads.
6) there will be an optimal acceleration. I don't know what it is but the Fit seems to not be terribly demanding. I have done some 6000 RPM shifting to get onto the 405 on the 270 degree uphill onramps and still gotten 34-36 MPG overall for 11 mile commutes.
7) don't use AC if you don't need it. Perhaps our brethren with Scanguages can tell us how many MPG AC costs.
8) use the best gear for the engine efficiency. The L15A17 is very forgiving between 1500 and 3000 RPM compared to a large V8. I suspect but haven't proven the AT outperforms the MT at 65 because the engine RPM is 2300 vs 3000. An LS06 Vette will accelerate hard in any gear because of the overflowing torque. For the diminutive L15, there are fewer choices for gears, especially uphill. At 65 you can downshift to 4th for more power, or it may be mandatory on a mild hill. 35 or 40 HP is all she got in 5th gear and each 1% incline will take another 5 HP. A 4% climb is about it without a downshift to grab more RPM and multiply torque.
9) Tires will run better MPG when inflated higher but care must be used to ensure they do not exceed sidewall ratings and understand that excess pressure will reduce the tire's ability to generate slip angle force (by stretching and holding the pavement) and hence permit hard cornering. I'm running 38 PSI warm right now and desire another couple of pounds. The Z-rated tires on my GTI corner very well at 45 lbs but were designed for it and easily outmanuever the Fit. The GE8 showroom cheapies surely are not made for 45 lbs, Honda says run 32. (One might think that a tire rolling down a road at 75 experiences a steady centrifugal force by the rim. That is very much not the case. Consider that a patch on the ground must come to a complete stop to hold the pavement, then accelerate to 150 MPH over the rim and then decelerate to another complete stop every revolution. Rim separation will happen during this acceleration phase where the bead can't hold the rim any longer. )
10) last but not least is speed, just slow down. 75 MPH is significantly worse than 65, and 55 is very good. I get nearly the same MPG slow and go on the 405 at 35 MPH with pulse and glide as I seem to do at 75 steady. Claims of 45 MPG at 75 don't seem physically possible. Wind resistance is measurable and very predictable. Coefficient of drag of 0.33 and 25.9 square feet lines up well with my coastdown observations.
my advice will not be surprising and should work for any car. The web has lots of videos and discussions on how to get the best MPG. The physics are to find out how much difference a driving change makes and quantify it, then it is up to you. Example is to use AC or not. We are blessed with a built in, but inaccurate guage, to teach us to drive skillfully. I learned my techniques on a 1995 GTI VR6 (has MPG meter) and was able to cruise at 30 MPG on a good day.
Best MPG:
1) long trips are best to reduce the penalty of warming up. Lots of short trips together are the next best thing. I don't have any data yet how much gas is used to reach operating temperature.
2) maintain a steady speed. acceleration is costly. This can easily be quantified with my models. And don't use the brakes if you can.
3) whenever possible watch the traffic and coast whenever it is safe to do so. Coasting in neutral with engine off is just about free, neutral with engine on nearly free, and coasing in drive least economical. In one future post I intend to show at what incline threshold you fail to get most of your energy back. This requires some math.
4) hills are extremely costly, therefore take it easy, let the car slow down if you can get away with it. Downhill, coast and even let the speed go a little high if safe to do so. My rule is 5 MPH under on the climb and 5 MPH over downhill will avoid tickets and road rage. If the hill is too steep to coast at a safe speed you will waste gas braking but use the energy to run the AC if that is beneficial. I tend to discourage you all from engine off coasting since your power steering will be off and you have only a small reserve of power brake left for the stop. You don't need power steering at speed but if someone cuts you off or a deer jumps out into the road it can be very dangerous. hybrids have aux power for forced auto stop, we don't. Besides, I don't know how much life the puny starter motor has, and the flat towing feature of the AT is probably not good at 75 MPH.
5) turns use more gas. How much depends on the slip angle of the tires where turning force results in parasitic drag. Hard cornering will increase rolling resistance. However I have used "scrubbing off speed" to drive route 20 from Corvallis to Newport with minimal braking on turns. It is fun and will outrun most drivers. Don't do this is you are not skilled at it! Oregon doesn't have guard rails on many roads.
6) there will be an optimal acceleration. I don't know what it is but the Fit seems to not be terribly demanding. I have done some 6000 RPM shifting to get onto the 405 on the 270 degree uphill onramps and still gotten 34-36 MPG overall for 11 mile commutes.
7) don't use AC if you don't need it. Perhaps our brethren with Scanguages can tell us how many MPG AC costs.
8) use the best gear for the engine efficiency. The L15A17 is very forgiving between 1500 and 3000 RPM compared to a large V8. I suspect but haven't proven the AT outperforms the MT at 65 because the engine RPM is 2300 vs 3000. An LS06 Vette will accelerate hard in any gear because of the overflowing torque. For the diminutive L15, there are fewer choices for gears, especially uphill. At 65 you can downshift to 4th for more power, or it may be mandatory on a mild hill. 35 or 40 HP is all she got in 5th gear and each 1% incline will take another 5 HP. A 4% climb is about it without a downshift to grab more RPM and multiply torque.
9) Tires will run better MPG when inflated higher but care must be used to ensure they do not exceed sidewall ratings and understand that excess pressure will reduce the tire's ability to generate slip angle force (by stretching and holding the pavement) and hence permit hard cornering. I'm running 38 PSI warm right now and desire another couple of pounds. The Z-rated tires on my GTI corner very well at 45 lbs but were designed for it and easily outmanuever the Fit. The GE8 showroom cheapies surely are not made for 45 lbs, Honda says run 32. (One might think that a tire rolling down a road at 75 experiences a steady centrifugal force by the rim. That is very much not the case. Consider that a patch on the ground must come to a complete stop to hold the pavement, then accelerate to 150 MPH over the rim and then decelerate to another complete stop every revolution. Rim separation will happen during this acceleration phase where the bead can't hold the rim any longer. )
10) last but not least is speed, just slow down. 75 MPH is significantly worse than 65, and 55 is very good. I get nearly the same MPG slow and go on the 405 at 35 MPH with pulse and glide as I seem to do at 75 steady. Claims of 45 MPG at 75 don't seem physically possible. Wind resistance is measurable and very predictable. Coefficient of drag of 0.33 and 25.9 square feet lines up well with my coastdown observations.
New Member
Joined: Jan 2010
Posts: 12
From: vishakapatnam,India
My buddy says a more powerful car wins MPG up a hill and I say no way. The Fit seems terrible uphill because it can cruise at 40 plus on a good day. If you get 22 MPG cruising it seems like your car handles hills very efficiently. It really does take a lot of gas to climb a hill and the Fit is still 2604 lbs empty vs 3200 lbs for the Firebird.
New Member
Joined: Aug 2010
Posts: 4
From: montana
Has anyone put there fit on a diet? remove extra weight etc. I mean really how much does a stereo and four speakers plus accessories weigh. Back seats? passenger mirror.Rear windshield wiper & motor etc. do i really need 2 wipers in the front? Has anyone taken the A/C completely out? I live in northern mountain zone not much need for A/C.
I wonder how much total weight and wind resistance you could really take advantage of..
I wonder how much total weight and wind resistance you could really take advantage of..
Member
Joined: Nov 2009
Posts: 1,222
From: San Antonio
+1!
I commute up a hill*, and have noted just watching the avg MPG readout that it does a whopper on my mileage. Thanks for calculating the mathematical reasons!
*hill = sea-level to ~400 feet in about a mile, stop-n-go traffic, and a speed limit of 25, so I can't coast down and regain it.
I commute up a hill*, and have noted just watching the avg MPG readout that it does a whopper on my mileage. Thanks for calculating the mathematical reasons!
*hill = sea-level to ~400 feet in about a mile, stop-n-go traffic, and a speed limit of 25, so I can't coast down and regain it.
Member
Joined: May 2010
Posts: 3,417
From: Capital Distric New York
A close look at the arrogance thrown at him and I can understand him leaving. The guy had a solid logic going and a few simply slammed him for no good reason at all..
New Member
Joined: Aug 2010
Posts: 4
From: montana
Sorry blassty, I could not find that thread you mentioned. But I did find a decent Rim/Tire Combo that would drop 35.59 pounds of total weight vrs stock steels n dun`s . If anyone has found better let me know.
And blassty If your not interested in mpg savings maybe you would like to know the performance value. Just keep looking for threads your so good at finding.
And blassty If your not interested in mpg savings maybe you would like to know the performance value. Just keep looking for threads your so good at finding.
Last edited by fitpizza; Aug 29, 2010 at 06:03 AM.
15"X7" Enkei RPFIs 9.5 Lbs...... 195-55-15 Conti Pro Contact tires 16 Lbs. The only wheel I am aware of that is lighter would be a Kosei 14"-6.5" that weighs 9.4 Lbs..... There is nothing you can do to your car that is better than lowering the weight of rotating mass and unsprung weight.... The ability to coast is not as good with lighter wheels and tires so you won't be as effective using that method to save fuel but your steering, suspension, brakes, clutch and other drive train components will work better and last longer saving you money in repairs and parts replacement..... You will also need less throttle to reach a given speed in the same time it takes you now.
Member
Joined: Feb 2008
Posts: 1,049
From: lake worth FL
You know Dok, you'd probably have better luck if you took a little time to read up on the topic. Even a bright guy like yourself might be able to learn from people who have posted extensively in the past on this topic.
There are several very good threads here on techinques to save gas, and several of those techniques directly contradict your advice. Generalized advice only goes so far. Nobody who has experience squeezing an extra mile out of each gallon in a Fit is going to take you seriously until you get up to speed on our cars.
There are several very good threads here on techinques to save gas, and several of those techniques directly contradict your advice. Generalized advice only goes so far. Nobody who has experience squeezing an extra mile out of each gallon in a Fit is going to take you seriously until you get up to speed on our cars.
Just wonder why someone would got to all the trouble to type all that and not have the facts. I got bored with it and found it missed key things covered many times, assuming best FE was the real goal as opposed to some math.
Tire pressure at side wall psi is a must. my My Sport Dunlap's run at 60psi. Never any issues at all.
Get a SG II and learn what it wants.
NO A/C ever I live is SE Fla buth up!
Max speed 55. I get 49mpg in my stk Fit with no wind at 55mph CC. just get in the far lane and try it.
P&G with FAS is huge. use the Fuel pump dash fuse with mom switch for the kill method. I have and can get 60 to 65MPG tanks all day long if I did this this all day.
have fun
Last edited by pcs0snq; Sep 5, 2010 at 06:01 AM.
Member
Joined: Sep 2005
Posts: 465
From: Central Valley, CA
91 Octane vs 87 Octane...
-macbuddy-
BTW-I tested 91 vs 87 octane to see if there was any advantage to using either. If you are interested to see what I found, here is a link to my test:
91 Octane vs 87 Octane, which is better?
Does 91 octane have any more (or less) BTUs of energy than 87 grade? I have seen a small, but detectable mpg increase when using 91 octane. I was wondering if that increase in mpg was due to a more energy laden fuel (i.e. 91 octane), or is the increase more likely due to the ECU allowing a higher advanced engine timing?
-macbuddy-
TW-I tested 91 vs 87 octane to see if there was any advantage to using either. If you are interested to see what I found, here is a link to my test:
91 Octane vs 87 Octane, which is better?
-macbuddy-
TW-I tested 91 vs 87 octane to see if there was any advantage to using either. If you are interested to see what I found, here is a link to my test:
91 Octane vs 87 Octane, which is better?
Don't mean to thread jack, but since this is about octane rating which after reading the thread, there has been discussions about better timing advance on higher octane rating and how it prevents pre-ignitions. I'm very well aware of these attributes about higher octane fuels.
My question is, especially to those people who highly regard the use of premium, I've have been testing also the use of 93 octane in my Fit (GE8). But my test involves not fuel mileage, rather the prevention of pinging.
I've done 3 consecutive tanks of 93 oct. and my car pings just as much with 87. If the 93 oct. did infact reduce my pinging, my ears tell me otherwise and only a computer will be able to tell if there is reduction pinging.
Seat of the pants didn't give me much either. Only diff. is that when the car is still not up to operating temp., the car tends to hesitate when I shift from 1st to 2nd gear. Once the car is warmep up, power is the same.
I know a scan gauge would tell me there is ingnition advance with premium (as stated by Texas Coyote many times and as well as other members in here.)
So my main question is why is there no significant reduction in pinging in my car to say the least if it does not TOTALLY eliminate my pinging.
Just for reference, I can hear it ping at about 4500 rpms and upwards. It does not continually ping all the way to redline but once my rpm hit 4500, I start to expect hearing my car ping. sometimes at 5k sometime 5500.
My question is, especially to those people who highly regard the use of premium, I've have been testing also the use of 93 octane in my Fit (GE8). But my test involves not fuel mileage, rather the prevention of pinging.
I've done 3 consecutive tanks of 93 oct. and my car pings just as much with 87. If the 93 oct. did infact reduce my pinging, my ears tell me otherwise and only a computer will be able to tell if there is reduction pinging.
Seat of the pants didn't give me much either. Only diff. is that when the car is still not up to operating temp., the car tends to hesitate when I shift from 1st to 2nd gear. Once the car is warmep up, power is the same.
I know a scan gauge would tell me there is ingnition advance with premium (as stated by Texas Coyote many times and as well as other members in here.)
So my main question is why is there no significant reduction in pinging in my car to say the least if it does not TOTALLY eliminate my pinging.
Just for reference, I can hear it ping at about 4500 rpms and upwards. It does not continually ping all the way to redline but once my rpm hit 4500, I start to expect hearing my car ping. sometimes at 5k sometime 5500.
Last edited by onemiglandicho; Sep 6, 2010 at 07:40 PM.
Member
Joined: May 2010
Posts: 3,417
From: Capital Distric New York
Bumped in respect to Doc
Also think it's current now, seein how there's a dicussion on fuel...
Also think it's current now, seein how there's a dicussion on fuel...
asianmoomoo,
my advice will not be surprising and should work for any car. The web has lots of videos and discussions on how to get the best MPG. The physics are to find out how much difference a driving change makes and quantify it, then it is up to you. Example is to use AC or not. We are blessed with a built in, but inaccurate guage, to teach us to drive skillfully. I learned my techniques on a 1995 GTI VR6 (has MPG meter) and was able to cruise at 30 MPG on a good day.
Best MPG:
1) long trips are best to reduce the penalty of warming up. Lots of short trips together are the next best thing. I don't have any data yet how much gas is used to reach operating temperature.
2) maintain a steady speed. acceleration is costly. This can easily be quantified with my models. And don't use the brakes if you can.
3) whenever possible watch the traffic and coast whenever it is safe to do so. Coasting in neutral with engine off is just about free, neutral with engine on nearly free, and coasing in drive least economical. In one future post I intend to show at what incline threshold you fail to get most of your energy back. This requires some math.
4) hills are extremely costly, therefore take it easy, let the car slow down if you can get away with it. Downhill, coast and even let the speed go a little high if safe to do so. My rule is 5 MPH under on the climb and 5 MPH over downhill will avoid tickets and road rage. If the hill is too steep to coast at a safe speed you will waste gas braking but use the energy to run the AC if that is beneficial. I tend to discourage you all from engine off coasting since your power steering will be off and you have only a small reserve of power brake left for the stop. You don't need power steering at speed but if someone cuts you off or a deer jumps out into the road it can be very dangerous. hybrids have aux power for forced auto stop, we don't. Besides, I don't know how much life the puny starter motor has, and the flat towing feature of the AT is probably not good at 75 MPH.
5) turns use more gas. How much depends on the slip angle of the tires where turning force results in parasitic drag. Hard cornering will increase rolling resistance. However I have used "scrubbing off speed" to drive route 20 from Corvallis to Newport with minimal braking on turns. It is fun and will outrun most drivers. Don't do this is you are not skilled at it! Oregon doesn't have guard rails on many roads.
6) there will be an optimal acceleration. I don't know what it is but the Fit seems to not be terribly demanding. I have done some 6000 RPM shifting to get onto the 405 on the 270 degree uphill onramps and still gotten 34-36 MPG overall for 11 mile commutes.
7) don't use AC if you don't need it. Perhaps our brethren with Scanguages can tell us how many MPG AC costs.
8) use the best gear for the engine efficiency. The L15A17 is very forgiving between 1500 and 3000 RPM compared to a large V8. I suspect but haven't proven the AT outperforms the MT at 65 because the engine RPM is 2300 vs 3000. An LS06 Vette will accelerate hard in any gear because of the overflowing torque. For the diminutive L15, there are fewer choices for gears, especially uphill. At 65 you can downshift to 4th for more power, or it may be mandatory on a mild hill. 35 or 40 HP is all she got in 5th gear and each 1% incline will take another 5 HP. A 4% climb is about it without a downshift to grab more RPM and multiply torque.
9) Tires will run better MPG when inflated higher but care must be used to ensure they do not exceed sidewall ratings and understand that excess pressure will reduce the tire's ability to generate slip angle force (by stretching and holding the pavement) and hence permit hard cornering. I'm running 38 PSI warm right now and desire another couple of pounds. The Z-rated tires on my GTI corner very well at 45 lbs but were designed for it and easily outmanuever the Fit. The GE8 showroom cheapies surely are not made for 45 lbs, Honda says run 32. (One might think that a tire rolling down a road at 75 experiences a steady centrifugal force by the rim. That is very much not the case. Consider that a patch on the ground must come to a complete stop to hold the pavement, then accelerate to 150 MPH over the rim and then decelerate to another complete stop every revolution. Rim separation will happen during this acceleration phase where the bead can't hold the rim any longer. )
10) last but not least is speed, just slow down. 75 MPH is significantly worse than 65, and 55 is very good. I get nearly the same MPG slow and go on the 405 at 35 MPH with pulse and glide as I seem to do at 75 steady. Claims of 45 MPG at 75 don't seem physically possible. Wind resistance is measurable and very predictable. Coefficient of drag of 0.33 and 25.9 square feet lines up well with my coastdown observations.
my advice will not be surprising and should work for any car. The web has lots of videos and discussions on how to get the best MPG. The physics are to find out how much difference a driving change makes and quantify it, then it is up to you. Example is to use AC or not. We are blessed with a built in, but inaccurate guage, to teach us to drive skillfully. I learned my techniques on a 1995 GTI VR6 (has MPG meter) and was able to cruise at 30 MPG on a good day.
Best MPG:
1) long trips are best to reduce the penalty of warming up. Lots of short trips together are the next best thing. I don't have any data yet how much gas is used to reach operating temperature.
2) maintain a steady speed. acceleration is costly. This can easily be quantified with my models. And don't use the brakes if you can.
3) whenever possible watch the traffic and coast whenever it is safe to do so. Coasting in neutral with engine off is just about free, neutral with engine on nearly free, and coasing in drive least economical. In one future post I intend to show at what incline threshold you fail to get most of your energy back. This requires some math.
4) hills are extremely costly, therefore take it easy, let the car slow down if you can get away with it. Downhill, coast and even let the speed go a little high if safe to do so. My rule is 5 MPH under on the climb and 5 MPH over downhill will avoid tickets and road rage. If the hill is too steep to coast at a safe speed you will waste gas braking but use the energy to run the AC if that is beneficial. I tend to discourage you all from engine off coasting since your power steering will be off and you have only a small reserve of power brake left for the stop. You don't need power steering at speed but if someone cuts you off or a deer jumps out into the road it can be very dangerous. hybrids have aux power for forced auto stop, we don't. Besides, I don't know how much life the puny starter motor has, and the flat towing feature of the AT is probably not good at 75 MPH.
5) turns use more gas. How much depends on the slip angle of the tires where turning force results in parasitic drag. Hard cornering will increase rolling resistance. However I have used "scrubbing off speed" to drive route 20 from Corvallis to Newport with minimal braking on turns. It is fun and will outrun most drivers. Don't do this is you are not skilled at it! Oregon doesn't have guard rails on many roads.
6) there will be an optimal acceleration. I don't know what it is but the Fit seems to not be terribly demanding. I have done some 6000 RPM shifting to get onto the 405 on the 270 degree uphill onramps and still gotten 34-36 MPG overall for 11 mile commutes.
7) don't use AC if you don't need it. Perhaps our brethren with Scanguages can tell us how many MPG AC costs.
8) use the best gear for the engine efficiency. The L15A17 is very forgiving between 1500 and 3000 RPM compared to a large V8. I suspect but haven't proven the AT outperforms the MT at 65 because the engine RPM is 2300 vs 3000. An LS06 Vette will accelerate hard in any gear because of the overflowing torque. For the diminutive L15, there are fewer choices for gears, especially uphill. At 65 you can downshift to 4th for more power, or it may be mandatory on a mild hill. 35 or 40 HP is all she got in 5th gear and each 1% incline will take another 5 HP. A 4% climb is about it without a downshift to grab more RPM and multiply torque.
9) Tires will run better MPG when inflated higher but care must be used to ensure they do not exceed sidewall ratings and understand that excess pressure will reduce the tire's ability to generate slip angle force (by stretching and holding the pavement) and hence permit hard cornering. I'm running 38 PSI warm right now and desire another couple of pounds. The Z-rated tires on my GTI corner very well at 45 lbs but were designed for it and easily outmanuever the Fit. The GE8 showroom cheapies surely are not made for 45 lbs, Honda says run 32. (One might think that a tire rolling down a road at 75 experiences a steady centrifugal force by the rim. That is very much not the case. Consider that a patch on the ground must come to a complete stop to hold the pavement, then accelerate to 150 MPH over the rim and then decelerate to another complete stop every revolution. Rim separation will happen during this acceleration phase where the bead can't hold the rim any longer. )
10) last but not least is speed, just slow down. 75 MPH is significantly worse than 65, and 55 is very good. I get nearly the same MPG slow and go on the 405 at 35 MPH with pulse and glide as I seem to do at 75 steady. Claims of 45 MPG at 75 don't seem physically possible. Wind resistance is measurable and very predictable. Coefficient of drag of 0.33 and 25.9 square feet lines up well with my coastdown observations.
Member
Joined: Sep 2008
Posts: 189
From: PHX
Does 91 octane have any more (or less) BTUs of energy than 87 grade?
Increased octane may/may not increase your MPGs. The only way it could feasibly, is as Texas Coyote says, allow the engine to increase advance. With the same advance, higher octane should actually generate less energy since it has higher resistance to ignition at a given temperature. This is different than the heating value, it is a property of the time it takes to ignite vs. the intensity of the spark.
Regardless, even if higher octane does increase your MPGs, I'd wager (and I do, infact, every time I fill my tank) that the offset doesn't make up for the increased price of the gasoline. In my area premium (91) is at least $0.25 more than regular (conservatively, it's often higher than this). Assuming $2.50 gas (it's actually a bit more right now), and MPG of 35 (according to Car and Driver, and also darn close to my estimates of 35.4MPG for what I get) you'd have to increase your efficency by 10%. I just can't believe the small amount of advance that you may be getting will increase your eff by over 10%. We don't even know for sure that the advance is occuring, all we has is seat-of-the-pants testamonials.
YMMV, try it for 10 tanks for yourself under similar conditions/driving styles, and settle on what works for you.
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