You need to see this as the weather gets colder there is a correction for air temp, coolant temp and load adding up to poor mpg. My SG says 36 but I have over a quarter tank at 300 miles so its around 38 or better. Heres the link Fuel parameters Also keep in mind that your Cold air kit can reduce mpg due to more cold air in the winter and help in the summer.

 

My last fill up, 3 days ago, netted me 30.5 mpg and this is mixed driving with long inbetween lights heading down 159th out in the country so to speak, going through Bolingbrook too. I'm sticking with premium for the winter and will see how it goes. Its been damn cold this week but last weekend when it was back in the upper 60's the OBC went right back up to almost 37 mpg....bring back spring

I'm sure my K&N typhoon isn't helping with mpg but with all the cold, dense air it seems to have a bit more pick up once its warmed up. Honestly, I don't really don't "give it the beans" that often, mainly because it doesn't have too many to give and its an auto, but the car sounds soooo good thoough

 

I'm about 3/4 through a 1500 mile trip from Atlanta to Delaware and back. For the northerly leg on Nov 22-23, I averaged (calculated) 39.63 mpg over 755 miles, burning regular gasoline. For the return (exactly the same route), I'm averaging about 37.1 mpg on premium. The only differences are, I got rid of about 75 pounds of cargo in Delaware, and it's about 20° cooler today, with a slight headwind. I won't make any judgements until I get back to Atlanta tomorrow, but it's certainly looking like there is absolutely no mileage benefit to spending $0.30 cents more per gallon for fuel.

 

This sort of test is not going to provide any real or conclusive data. There are too many variables and too few controls.

The closest you are going to get to tangible data would be to get a scan gauge and note how much spark advance, throttle position, and what lambda values you are seeing between the two fuels under similar driving and atmospheric conditions..

Even then with a 20* change in IATs between tanks, the results will be all but useless.

One tank to the next you aren't going to see that full effect from either fuel because your long term and combined fuel trims haven't gone through a full "driving cycle" Even if you reset the ECU in between tanks there would still be time required to drive around and let the computer decide which maps/tables are best suited to conditions.

That $0.30 also is buying you more detergents, upper cylinder lubricants and a tidier blend of hydrocarbons. These also change brand to brand which would dramatically impact any results you report.

 

I've been told to try BP for best results, I'll be doing that next couple times out to see what's what. I've been using Shell because of the C&D ad there, don't usually do that but I thought the car mag might be onto something.

There are so many variables for sure, but cooler weather and that headwind do add up, but as you can see, you didn't go down that much with those two things going against you so I'd say the premium helped out. I used to think that the use of premium in the Fit was a waste, a small one at that because when you stop and look at it, on a half tank its what, $1.00 extra

 

I agree with you entirely, and on a suggestion from silverbullet, I as well may be giving BP a shot.

But I'll do it with the Laser which is a bit more demanding on fuel and should give more obvious results!

I have both a BP and a Shell within 1.5miles from the house and for control I always go to Shell and use their 93oct.

It should be as obvious as filling up, warming up and then building 15-20lbs of boost and seeing if the WB dips rich while timing is pulled (knock retard) or if it gives me a nice full pull, leans out a couple tenths and advances the spark more with the same amount of throttle input.

My methanol kit and computer are out of the car at the moment because I am still dialing in my new VE table since I can't seem to stop modding the darn thing for more than a couple months at a time. So the results will not be skewed by having a water/alcohol mix spraying on top of it.

Just BP 93 v. Shell 93, and even only 1.5bar boost will usually seperate the men from the boys.

 

Sunoco doesn't offer 94 anymore, every little bit helps, right Hell, I haven't seen a single Sunoco station in the greater Chicagoland area for that matter. Then again, you guys have stations here that we don't back home in Detroit, like Phillips 66 for instance.

 

I remember the 92 octane at union 76 , it was great stuff. Methane is a high octane(120+) gas that was used in gasoline until 1990. The clean air act changed that and new formulas(ethane 20-30 lower octane and butanes) had to be made. Sunoco ultra 94 was basically the 92 octane base fuel and 10 percent ethanol. Ethanol has been used in BP since the 70's. Bp (standard oil) had unleaded fuels since WW1 while other brands used leaded fuel for easier octane increase. Sunoco is very similar to BP. Tried it and like it, mpg was a .5 mpg lower that BP hardly enough to notice. Sunoco is east of Indiana with a few still south of Indy.

 

I used Shell and was disappointed too. 33 mpg in 1 tank and when I went back to BP it went up to 38 for the last few tanks but is dropping (36mpg) because of the cold. My scan gauge says its still running in MBT timing 25-45 degrees of timing. I have also noticed its using more fuel at idle because of engine loads(lights,heater,turn signals,and even brakes) on engine but I am still able to get good mpg. Octane difference only cost 6-10 cents to make and the rest is additive cleaner and upper lubricant. If you went to Walmart and bought a injection cleaner with lube you would spend 9.00 for a bottle and would need to use it every 3 rd tank to equal the benefit of premium gas. They say on bottle to use it every 3000-5000 miles but if you fill your tank and run it to 1/4 tank you will have no cleaner after the 3rd tank. I see the benefits = the easier starting and better acceleration and mpg plus cleaner engine using premium.

 

I disagree. I controlled for every variable that I could, leaving only weather; light variable winds on both legs, but for the most part, nearly still, clear, dry air all 4 days. Same driver, almost exactly the same route, same load, same highway speeds (60-75), mostly the same gas stations, and obsessive attention to getting consistent fills (gasoline visible at the top of the filler neck). Tire pressures were checked at the start of each end of the trip (37F, 35R). The oil minder read 80% at the start of the trip and 70% at the end. When I arrived at the northern end of the trip, I filled a nearly empty tank with premium gas. On the return leg, I drove 10 miles before the first fill, to eliminate cold weather warm up mileage, and did not include that fill in the results. Thus, all driving, except for the morning of Nov 23 (regular gas) was at highway speeds with a warm engine.

Here are the data:


November 22: Atlanta, Start: 52° Henderson, NC, Finish: 65°
November 23: Henderson, NC: Start 54° New Castle, DE, Finish: 55°

Date Mi Gal Calc Meter
November 22, 2010 192 5.00 38.40 40.5
November 22, 2010 156 3.95 39.49 41.7
November 23, 2010 407 10.10 40.30 41.2
Regular Gas: 39.63 avg mpg Atl-DE, 755 miles

November 27: New Castle, DE, Start: 32°, Dahlonega, GA, Finish: 42°
November 23: Dahlonega, GA, Start: 48° Atlanta, GA, Finish: 52°

Date Mi Gal Calc Meter
November 27, 2010 96 2.60 36.92 36.9
November 27, 2010 88 2.36 37.23 37.9
November 27, 2010 363 9.80 37.04 37.5
November 28, 2010 200 5.60 35.71 37.5
Premium gas: 36.68 avg mpg DE-Atl, 747 miles


I am not making any power claims, only reporting carefully recorded consumption figures. If you have better data, post it. Recently there was some discussion on various Linux lists about a performance tweak, in which one of the participants (who had the numbers) said, "Numbers talk, bullshit walks."

I side with the automotive engineers and fuel system engineers who have, over and over again, stated that on an unmodified engine for which the manufacturer specifies regular fuel, using "premium" gasoline is a waste of money. But the gas stations and refiners will love you, because they have a higher profit margin with premium.

 

Thank you for taking the time to post your actual results. You appear to be a very disciplined driver, and I wish I could say that about people more often

But let's get something clear, the L15A has a minimum octane requirement, and that minimum IS 87.

With all the quench surfaces, extra coolant passages, oil squirters etc available in this day and age, our engine is still a 10.4:1CR. There is no getting around that except for copious amounts of fuel used to cool/slow the combustion and having to pull timing to prevent knock to allow 87 to run safely.

The reality is that the car will perform better all around on 93. Everything from throttle response to mileage will be affected.

Here is why, start on page 5.
https://www.fitfreak.net/forums/2nd-...tml#post936382

There are more than a handful of forum members with actual OBD2 scangauges posting their data and testimony on 87 v 93. All of them concede that 93 is superior. That is not an exaggeration either.

You will probably notice there is a gentleman by the login of Steve244 who insisted on learning all this the hardway.

I tune vehicles I drive daily, as well as others for clients, family, friends and those that I put through hell in standing mile and Land Speed competition on my own time in the spring and summer.

I can tell you exactly how the ECU operates and why, in addition the to physical conditions sustained in the combustion chamber and why most can benefit from 93 on the L15A.

The only recommendations from Honda regarding 87 octane in the Fit is that you do not use anything below 87. Like many things in life, you CAN get away using the minimum, but on my $17k investment, it is worth the extra couple dollars on a tank that I fill once a week.

There is no BS in what I am posting, and I am an engineer, FWIW.

The Fits were NOT calibrated with 87oct used to make the MaxOct Timing and Fuel maps. 87 is the bare minimum you should use.

If you want to run 87, that is perfectly fine, there will be no damage or any adverse effects. If some of us choose to use premium, we will reap the rewards.

 

I've been following similar threads (generally the same half dozen people involved -- you know who you are) in this forum for the past year. One of your posts, on page 6, stands out:

Over 9 more pages of discussion, that remained the case -- nobody provided any A/B data on regular vs premium fuel for a given model Fit (in my case a 2009 Sport AT) in real world driving conditions. Lots of anecdote, lots of theory about why things should be better with premium, but no actual real world data.

I have posted detailed consumption figures over approximately 1500 miles, controlling for as many variables as possible, that show no MPG improvement for premium gasoline -- arguably the opposite -- in an unmodified 2009 Fit Sport AT. If someone here can post better data (for example, with less outside temperature variation), it would be helpful to the discussion. I doubt that the temperature variations over this trip were sufficient to explain an 8% difference in fuel consumption, especially since I eliminated cold weather warm-up as a variable when I switched to premium. In the absence of published data to the contrary, I stand by my statement that I see no measurable improvement in gas mileage for premium vs regular gasoline.

 

Speaking of which, the plural of anecdote is not data, and one data point (you) does not constitute a trend.

That is your opinion, you are welcome to it. With that said, I maintain mine on your data. There is much you are not considering, and factors as minor as 5* difference in IATs or coolant temp can amount to a significant change in the combustion chamber.

It is a shame you only skimmed the thread I linked for you to cherry pick a quote and ignore the last few pages where people had actually switched to premium and shared their results. Scratch&Dent being the most recent example, and he like Klasse Act were skeptics early on.

Not too mention all the links by several contributors as well as the ECMLink download, setup and tutorial I posted.

There is a lot of information there and through the links and images contained within, and for you to pretend that you can go into this topic knowing none of it, or maybe a sliver to be generous, and then after a few minutes of glancing at that thread be able to sound off so confidently is just silly to be honest.

There is far more to the regular v. premium debate than just the octane number and knock protection.



To avoid mucking up Klasse Act's informative thread, where his findings and those of others conflict with your opinions and hand calc data... create your own thread.

 

RFG gas has 8 percent less BTUs than Conventional gas splashed with ethanol and the mpg difference between is usually opposite 36 for reg and 38-39 for premium gas. You also didn't take into consideration the wind usually goes south to north so you had a back wind pushing you there and on the way back you were going into the wind with RFG gas. All the sources say premium at least has 2-3 percent more Btus and run the engine more efficient. If they took regular 87 and splashed in 10 percent ethanol it would be 90.5 octane and then I would agree with you that 93 would not make difference but they use cheaper stocks more kerosene and put more ethanol in which when pressure builds it causes the rest of the mix to ignite from compression like in a diesel and is wasted because the timing retards and all the heat goes into the engine complicating the problem. Premium gas flame front burns faster not slower and builds up more pressure because no knock which causes a more efficient burn with a cooler running engine. Heat is what destroys an engine but it can be your friend if it controlled.

 

Exactly.

E10 gasoline also runs a richer AFR in addition to lower energy density per unit volume. Which is why your economy can suffer 7-8%, and more when the fuel used to reach 87 oct is mixed with a 10% blend of ~114oct Ethanol dumped in. Which tells us right there how poor quality that fuel can be.

Stoich for E10 is 14.1:1AFR, Straight Gasoline is 14.7:1

 

If I had wanted to write "many anecdotes" I would have. "Lots" does not require a plural in the use I made.

I have provided 7 data points on regular vs premium fuel consumption. Nobody else has provided consumption data with anywhere near the same level of control for variables. These are facts, not opinions.

 

The heat from the retarded timing pulls heat in to cylinder head and then the cooling system, it causes the ecu to add more fuel to slow the burn but it only adds to the problem. We Know what RFG gas is compared to most people on the forum. Since 1990 we have had RFG and had issues with regular. Adding ethanol to gasoline doesn't make it RFG but the same problems still exist.

 

DSM,

Just a few quick points/Q's

3 posts up you "state" that the L15 retards timing to prevent knock on 87 octane. Later you state that the L15 was not designed/calibrated on 87. Is there any information about this? (Edit... a fair more than 3 posts by now... Sigh)

My understanding of the issues surrounding higher compression was that the heat generated due to higher compression was the primary reason for pre-detonation, hence the need for a higher octane fuel(to resist heat/pre-detonation). If honda were able to sufficiently cool the chamber to prevent this, there would be no need to use anything higher than the minimum. From what I've read, this has been achieved.

My Altima had Premium recommended for best performance but was rated to run on anything 87 or higher. In this case, the VQ35 would retard the timing a little bit. The manual stated that the maximum power could only be obtained using premium. Honda makes none of these claims and with the new "war" in showrooms being subcompacts such as the Fit, Mz2, and fiesta, every company is going to max out their numbers. if honda could get increased performance and economy by simply changing some wording in the manual (use premium for best performance/economy but regular is just fine for the engine) they would state it. It would also help the CAFE numbers and allow Honda to market the fit with higher economy numbers.

As a side note, I'm at 38.2mpg lifetime at over 20k miles. Only about 600 miles of that was on Shell premium (93) with 0 increase in economy. (Never attempted to see if I had more power) The rest was regular (Citgo/Shell/Exxon (87))

~SB

 

Yes 7 data points from one car with controls that only you are satisfied with to stage your claim that there is no difference between regular and premium. Your figures are just as valid as Klasse Act's, Silver Bullets, S&D, Texas Coyote's and my own to name a few.

The difference being, you are the only one not seeing similar behaviour.

You like, Steve seem to think this is some sort of oil company conspiracy and they are trying to con you out of ~$0.20/gallon.

You realize it is more expensive for them to have to produce premium? It is not just arbitrarily more expensive at the pump. The whys and hows are the important bit and you don't seem to have even a basic understanding of this.

Where do I or anyone else reporting success on premium, benefit from having you switch to premium as well?

Your own data shows that in spite of 20*F colder air temps you managed better economy on premium (37.1mpg) versus regular (36.9mpg)

This is because that even though denser air means more air makes it into the engine at a time so more fuel is needed, you were able to run so much leaner on 93, that in fact you used slightly less fuel despite a dramatic change in weather So an otherwise insignificant gain when put in context becomes pretty remarkable..

Besides your original premise was this:

Honda themselves will tell you regular 87 is the MINIMUM recommended. They do not specify regular, they say you should run nothing lower than 87, which is regular.

So even your own anecdote shows you have no idea what you are talking about.

Why is it all these clever computer guys have no idea about what goes on inside an ECU?

 

If you read closely you would see i state specifically that the MaxOct Fuel/Timing tables were not done using 87, those were likely done using the equivalent of 95-96 octane based on what is sold in Japan. 87 is at the lower-middle end of the fuel spectrum in the various markets the 10.4:1CR L15 is sold in.

You can find MBT timing on 87, but it is not the only MBT achievable with the engine, different fuels have different MBT. Even 93oct can see knock retard and richer mixtures based on IATs and Coolant temp in addition to what the knock sensor sees.


Not everyone has access to 99RON (like in parts of Europe, Japan, Hong Kong) or the US 93oct [(R+M)/2], 87 is a good common denominator because it is not the lowest grade available, but one of the most common, it is for the most part the lowest grade you can get in the USDM however. This is why they require it as the minimum.

The implications of compression are more complex than that, but that is a good starting point, and the higher octane (more stable) fuels resist pre-detonation (knock) better under these conditions. But with retarded timing and a somewhat richer mixture 87 can run safely. There is no way to run the same timing/lambda MBT targets on 93 that you would with 87.

Old school tuning would dictate ~100octane on a carburated and mechanically timed 10.5:1CR motor. The only reason we can get away with 87 using EFI is through the computer being able to monitor and alter events on a per cylinder/per rev basis and employing oil squirters, extra coolant passages and enlarged quench surfaces on valve seats as well as the piston crown.

Fuel is only part of the equation, what the ECU does to the timing and fueling schemes plays a huge part, and that still doesn't cover everything from atmosphere, vehicle load, gearing, cam specs, sensor feedback and driver input.

If you really want answers to all of your questions, go to the thread I linked above, read all the Hondata and other articles, download the ECMLink app play around, follow all the demos, and the go buy yourself a scangauge and watch in real time the concepts we are discussing.

Edit: here are a couple links that will provide a very elementary introduction on how compression ratio effects things, and why a 10.4:1CR IS significant and very much a "high" compression engine (for pump gas):
http://auto.howstuffworks.com/fuel-e...uestion901.htm

http://en.wikipedia.org/wiki/Compression_ratio

For more you can check out some of the later pages in my tech thread:

https://www.fitfreak.net/forums/fit-...ater-meth.html

To answer your last point, Toyota among others got in trouble by inflating their CAFE numbers through using premium in vehicles where the suggestion in the manual was regular. The new Hyundai Genesis for instance has different ratings for economy and output based on fuel quality. For the most part people buying the Fit have no interest in these things. So to keep inline with the idea of economy, cheap to own etc they will tell you regular is fine, as long as it is greater than or equal to 87 octane. Depending on where you live and what style of commute you have the long term cost/benefits of regular v premium may negate eachother. For some who are consumption conscious but occasionally put our foot down, the benefits are worth it.

For those who do baby it, the extra detergents and top-cylinder lubricants are worth the ~$2-3 bucks at the end of a 10gallon tank, IMHO.