The SG just displays 4 at a time where the ultra displays 6 on 3 screens for a total of 18. The SG does not display fuel trims for a Honda.

Weight matters but not that much heavier cars coasts faster down hills so its a draw to advantage. Keeping extra weight like tool boxes and things not need in an emergency will help save on mpg over time.

 

It's not quite a draw, between uphill and downhill, but of course if you're driving only from A to B and not back again unless you're really sure the ground is totally flat you may not be driving both up and down the same amount of elevation.

The problem here would be finding a place with no traffic, to do the test, unless we do it at 3 AM...

 

I notice that I get better mpg when tank is full than empty. So for me a full tank is best. I know people who use there cars as storage, using the back for tool boxes, oils, jacks and what ever you would store in a garage. The fuel tank in the Fit is under your seat so it also helps with center of gravity. Driving on asphalt hurts mpg compared to concrete. Driving 45 is better than 65, but I get 33 mpg at 75. In the summer I get 40 at that speed and the mpg meter says 60plus mpg. We have foot hills here and its not always flat. I live next to the lake and the glacier push up the land around it. The center of the state is flat but the west and south is very hilly.

 

I can't see any way you'd get better mileage with more fuel in the tank under similar conditions but perhaps you're buying gas when your car's already warmed up, so if that's when you reset the trip odometer it'll seem like you're getting better mileage.

Similarly, I get horrible mileage when I fill up, but that's because between the gas station and my house are eight traffic lights in nine blocks and it's uphill.

 

It's crazy how many things that affect fuel mileage... I went to 10-30 Mobile1 and a few ounces of Lucas synthetic oil stabilizer to see if it would help with the blow by I had been experiencing, went back to my lighter wheels and have seen a loss in fuel mileage... I am actually getting decent mileage since there is a difference in diameter with the tires I presently am using being the larger... The reduction in weight has improved acceleration by a little even with heavier oil, the larger tire diameter and additional rolling resistance of the MS rated tires but when I figure my mileage at the pump I am down about 4 MPG... Another thing that I am sure has influenced the change is the amount of urban driving I have been doing and not using octane booster... You aren't kidding about the southwestern part of the state, it is very much like central Texas but I couldn't help but stretch the legs of an old beater Volvo wagon over on long flat stretch about 15 years ago even though it was still the era of "Stay alive... Drive 55" . Driving at night on rolling terrain when there is very little traffic is where I ease up on the throttle going up and gradually accelerate toward the bottom of downgrades to take advantage of gravity to conserve fuel... I seem to do that kind of thing much more often since upping the boost.

 

Its funny that people worry about a full tank compared to the extra weight they haul around. As the tank gets lower the octane lowers too, because the light ends take up the room in the tank. Then theres water vapor that forms in the tank and fall into the heavy ends and can cause fuel separation. Keeping the tank full is the best for mpg and keeping the octane level steady.


Dee, I might try regular motor oil in your car. It should help with blow by, by not being so slippery. I noticed the problem when I put motorkote in my fit. The mpg dropped and I am pretty sure its cause by improper sealing of the rings. I just got gas and put in midgrade and the last tank gave me 34 mpg and the fuel trims are -5.5 and still pulling fuel. The timing at idle is near 0 and was 6-8 with premium. I will go back to premium when the temps go up. Its also rain here today and the barometer is low so its like running higher octane. I expect the trims to 0 out later in the week when the low pressure moves away. High pressure requires higher octane and I have been noticing that too.

 

If you have lots of hills you need to try higher octane, more power less fuel used going up. I get gas no lower than a quarter tank, the lower the tank the more light ends go back in the station tanks and thats part of the problem of bad gas mpg. The light ends like isobutane is a gas like in a lighter and is high octane and evaporates easy.

 

I have let my car sit at a half tank with out being driven too much in the last three weeks so that has probably contributed some what to what is going on.. The last fuel I put in was Exxon and within a few miles I could tell it was bogus from the smell of the exhaust fumes... Where I was getting ignition timing advance readings in the upper 40s under small throttle settings and light engine loading 36 degrees has been the max without octane booster of some sort... Regardless of all of the post that say otherwise, this little engine setup just loves the hell out of octane and the ECU stock or otherwise makes the most of it... I remember that you had talked about MotorKote and I read good stuff about it.. Even though 10 PSI was considered chump change and pussy in someones post I read it is still enough that blow by becomes an issue but the only hassle so far has been that the rear of the car becomes lightly coated by tiny minuscule oil droplets after 4 or 5 thousand miles using 10-20.. The heavier stuff with the even heavier stabilizer and an occasional wash job should do the trick for the time being, maybe 10-50 oil when it gets warmer... The barometric ups and downs and 20 pounds of weight gain that I acquire every winter is doing a number on my arthritic joints as well as messing with your mileage figure and gauge readings and the liquor stores are closed on Sundays so I have to wait to put ethanol in my tank to ease the pain.

 

Premium should stay more stable and I am lucky to have good gas around here with BP. I would adjust the valves, the blow by most likely is coming from there. Hondas are notorious for valve stems leaking especially when the valves need adjusting. Ive seen that problem on a lot of Honda motors and not just new ones. The vibration cause oil to go by the seals and then you add boost so I am sure thats the cause.

I get my to see my sons car get tuned soon and have a big list of thing to do before that. Hopefully have a few different tunes 5,10 pounds on premium and a 14 or more on 100 octane racing fuel.

 

Damn man... my ignition advance is around 25° at a steady 50mph on a flat road on 92 Octane! In our sub 0 weather, it seems like there is no difference between 87 and 92 octane as well as my ignition advance remains in the 17-18° range at WOT and around 24-25° at a steady 50mph! In my car, premium fuel seems to work best in summers high temperatures! Maybe American and Canadian Fits doesn't get the same programming, our fuel sucks or it doesn't understand what happends when it sees sub zero °f ambient temperatures!! Anybody have an idea about this?

Marko!

 

I have the same problem. The highest ignition advance I can reliably get on 93 fuel (!) is 35-36 degrees. I get that timing at 48-52 load and about 2000-2500 RPM. WOT values I get are 4 degrees at 1500 RPM, rising to 12 degrees at about 3000 RPM on 87 fuel, 12 degrees at 1500, rising to 17 degrees at 3000 on 93 fuel. Figures are very similar for a blend of E70 with 30% 93 octane E10.

What gives?

 

If my car not done the same way before the ECU reflash I would have thought i was getting more ignition advance because of the tune... The timing immediately drops when there is more than just a slight bit of boost dropping down to 3 or 4 degrees at full throttle also... with the 5 PSI base kit and Super Card tuning using octane booster under the optimal conditions the timing advanced into the mid 50 degrees on occasion but very briefly and would pull back to around 48 and that was when the ambient temperature was around 80 degrees.... DOHCtor, the automatic transmission cars have a different ECU than used on manual equipped cars and may be why you don't see as much advance.

 

Mine is a manual. You think maybe it's the Super Card?

 

No, I got the same numbers as you do on 93 octane fuel before the KWSC at 5PSI boost and after with the Hondata reflash and 10 PSI boost.... The octane booster is what allows for the higher degrees of advance.... Even with just a SRI and axle back pipe before I boosted it did the same... There is also more power according to my tired old wrinkled and experienced butt dyno.

 

So, you think if I use octane booster it will jump up to 40's timing? If so, what octane booster is good? I'm okay with using ethanol and the like, but I don't want to use MMT.

 

A half-gallon of 118oct paint thinner per tank would do the trick!

5 gallon cans are usually $30-35/each at home depot or a sherwin williams paints store. So thats ten tanks per can and you will see far more radical a change than even multiple pint bottles of octane booster

They both work, but the actual change in [R+M]/2 is usually less than one octane point over a whole tank. Even if the bottle says 100+ or whatever.

The B-12 stuff is pretty potent but expensive and comes in small bottles.

Toluene is already a pump gas constituent and is more energy dense so fuel economy goes up as well as the ability to run comparably leaner so a two fold economy advantage as well as how much more aggresive a timing scheme the ECU will be able to get away with.

 

1. I am not an automotive engineer, or any kind of engineer for that matter. Therefore, any conclusion I reach is invalid.
2. I do not race cars. Therefore, any conclusion I reach is invalid.
3. I have built and rebuilt engines for a living.
4. I own a Scangauge.
5. My '07 Fit is stock. Therefore, any conclusion I reach is invalid.
6. I have used mostly Shell regular gasoline for my '07 Fit's 90K+ miles.

I tried 15 tanks of Shell Premium gasoline in my Fit. Immediately when I started using Shell premium gasoline my gas milage dropped from an average 31 mpg to 28 mpg and stayed at this level. I could not tell any performance difference (no dyno or track testing just "seat of pants" feel). When I went back to using Shell regular gasoline my gas milage returned to 31 mpg.

 

Any chance you could share scangauge data, climate, commute description?

Because there are bound to be outliers in the field and that experience directly contrasts with most of us, so it would interesting to see what the ECU had to say about the matter

 

Did not track any data. My daily commute is a 56 mile round trip hilly interstate drive cruising at 78 MPH. other driving (also mostly hilly interstate) mixed in. My Fit is a Sport automatic.

 

Anything you can think of that would contribute to this?

Obviously every single engine, even between identical builds churn out different results under identical situations, but I wonder why you would average a 3mpg loss between premium and regular.

That goes against basically everything I've been taught and seen in the field, which happens more often than any instructor will let on. I do occasionally see counter-intuitive results as I go along. Like the occasional setup that prefers more timing over more boost on pump gas. When the vast majority I have come in contact with like boost more than timing.

One of my personal anecdotal examples being a stock 2.0L making 300whp on 18psi and 8* peak timing @ WOT v. an identical 2.0L setup making that same 300whp but on 10psi and 21* timing on the same compressor and fuel from the same station..

Practice v. Theory always makes for some interesting situations! Thanks for chiming in! Maybe when you get a chance could you check out what sort of timing/FT's you see across the board? (idle/cruise/wot)

I am curious to see what my L15A1 will do under boost. I, Tex and others see gains on 87 v. 93. I also picked up timing across the board going to a colder plug.

I am planning on running a rough experiment for my own edification when it gets nice out, which will be 87 pump v. 100 octane of my own blending.

Your mileage should improve regardless of fuel if you cruise around 60-65, unless that is going to slow for traffic/personal preference!