Fuel Type Questions (Novice Here)
 

I've always wondered the facts from the fiction when it comes to the three (or more) types of gas you get to choose from at the gas station.

I was wondering if it's smart to use the highest "premium" version on the fit, to keep it in a better condition? Considering we only have a 9 gallon gas tank with great MPG - a few extra cents a gallon should be no big deal.

But I'm curious if it's actually even worth it?
Can anyone shed some light on the difference between the types of gasoline? Is it just an elaborate scheme to waste accumulative cents for a false reason on the unknowing?

Thanks.

Higher octane rating is specifically for engines that requires it for that thing they call "engine knocking" or detonation. As for the Honda Fit, it says in the manual to use fuel with octane rating of 87. Hence, to save money and unnecessary fuel particles, go for the regular (octane rating 87). Lastly, higher octane rating does not also make your engine cleaner -- they are all the same.

^^^ what he said, don't waste money on higher octane gaz, get the good ol' regular ;)

The manual says that 87 octane is the lowest that can be used in the Fit.... The ECU will retard the timing to not have the engine ping with lower octane fuel and allow more advance with premium and improve your gas mileage and performance as well as contributing to less carbon deposites in the combustion chamber..... The 2007 model has a 10.4 to 1 compression ratio which would have called for leaded premium (ETHYL) gasoline back before unleaded fuel and ECUs.... The premium fuel used in other parts of the world is rated as high as 97 octane and Fit owners that use it in their cars continue to do so because it makes them faster and again get much better fuel mileage they claim justifies the price.

So Texas Coyote, you're saying it would be (if I felt the extra price was worth it) a better idea to use the most premium offered gasoline? Due to a better economy gained, more environment-friendly and/or better horsepower? If I'm reading that post right..

Thanks for all the great information guys.

I am sure that there are people that will vehemently flame me for saying so, but yes..... Get out the owners manual turn to page 132 and see if it says to use 87 octane, or if it doesn't say "87 octane or higher". .... The same people that complain about the performance of their cars are using regular grade fuel and in some cases non synthetic or heavier than the recommended 5-20 wt oil..... I fill my car to the top to accurately check my fuel mileage and always average over 37 MPG unless I am driving fast and hard in city traffic. I am only getting around 33 at the moment because I am having too much fun with my new super charger but once I can control my impulsiveness I think I will be bringing it back up closer to what I was getting.... If you are now using regular,smell the oil dip stick and you will find that it smells like gasoline., that is because when the timing is retarded the fuel doesn't completely burn and gets into the oil by washing down the cylinder walls and causes premature wearing or the walls and rings...... Be kind to your ass for it bears you.

Very interesting, I will try that dip stick technique.
It seems to me, considering the small amount of gasoline I need once/twice a month due to the Fit's amazing gas mileage is well-worth it to splurge on the minute increased price of Premium.

My next tank, I believe I will be switching to Premium. Thank you for all your insightfulness.

If you don't mind me asking about your super-charger though, however off-topic.
Cost? Did you install yourself? Well worth it?
I'm interested in supercharging, of course I'm sure I could never afford it - but the thought is so provoking.

Check out the Kraft Werks ad at the top right of the page and the forums related to it. I installed mine and I am disabled and close to 60 years old. They are about $3500 for the 5 lb. boost and I would guess another $1000 or so for the 10 lb. boost when it is available. I got mine for $2700 before the price increase and I like it...... I am not into shiny geedunk and couldn't care less if someone thinks my car is ugly, but I do like to drive a good handling car that pulls hard out of curves, so for me it was worth the money but only because I had it at the time and didn't have to use a credit card.

Modern engines and ECU's will not advance ignition timing given a higher octane fuel than it was designed for, it will only retard it on the chance that something lower than it was designed for is put in. Nor is static compression ratio a good gauge for what octane will work best in the car . . . you need to calculate in many other factors, such as dynamic compression ratio, piston and combustion chamber design, engine operating temperatures, typical load, etc. etc. 50 years ago a 10.4:1 compression ratio running on 87 octane would have been near impossible, and 30 years ago it would have been remarkable . . . But these days, it's fairly commonplace.

Not exactly an accurate test of whether your timing has been retarded. I use regular exclusively on this car, and my last oil analysis showed a fuel percentage of only .8%, which is quite low, especially considering I took the sample from a cold engine.

An even more accurate (and immediate) test to see whether the 87 octane is holding back performance would be an OBD2 scanner. Just log out timing advance using the 2 different octanes, and you've got your answer.

You can find examples where the difference between premium and regular gas has been dyno tested on cars rated for 87 . . . in every one I've seen, the higher octane fuel does no better - and usually does worse. There's nothing in the Fit's design that makes me think it'd be any different. :shrug:

There was a guy a while back that used a scan gauge on his car and reported a difference in timing advance using premium fuel opposed to regular on the economy thread.

AAaaah . . . now that's really interesting . . . Searching for the info now, not much luck yet. Just need to get my laptop up and running, and I'll be able to check it myself.

If, in fact, a fuel w/ an octane rating greater than 87 allows the ECU to advance timing more, the next question is: Does that actually equate to a more efficient engine? (and of course, is the difference significant enough to offset the increase in fuel price?) No easy way to test that w/out a dyno . . . Maybe an accelerometer like a G-tech is sensitive enough, I dunno.

The post was by DOHCtor on page 8 of "Octane 87 89 91 93 95" Eco FIT. He has all of the results of his findings and proved it to himself and a lot of others. Check it out.

The difference between regular, intermediate, and premium gasolines is based on the octane rating, or the ability of gasoline to avoid combustion from compression heat before ignition by the spark plug. The higher the engine compression the more likely to get precombustion, or spark knck,. It has a knocking sound like rapping on a hardwood surface, hence the name. reg is 87 to 89 octane, intermediate is 91 and premium 93.
our Fits don't have a high enough compression to warrant more than the regular gasoline.
However, gasoline does leave deposits that can inadvertently raise commpression and the best way to avoid that is monthly adding one can of injector cleaner to your gas. WallyWorld sells a good non-alcohol one at about $1.50.
The only reason to ever use premium is for slightly higher mpg as premium's mixture of component chemicals has a somewhat higher energy content so you get more 'push' from its combustion. Usually though, the added cost doesn't justify the gain in mpg.

PS all gasolines are a combination of many chemicals; they may vary even from the same brand simply because refineries are that fixed on processing conditions and selection of crudes.

We had the chance to talk with some of my lab people and they said gasolines in general were losing energy potential. Some heats of combustion measure as low as 108,000 BTU and even premium isgetting results as low as 111,000. Has to do with increasing volume output from the same crudes. In general premium still has a slightly higher Heat of combustion but it still isn't worth the price increase.

Here's a link to the post. (Certain people should learn how to post links, ahem...)

https://www.fitfreak.net/forums/fit-...tml#post481366

Very interesting results indeed! I wonder what it all means though for steady state cruising, which is mostly what I do on my commute.

It seems to me, with all these results - there really is no NEGATIVE to using a premium gas type, considering the price increase is nearly negligible when you use a 9 gallon tank in a 32-34mpg car.

I understand that the POSITIVES to using it may also be negligible, but at least the negatives are non-existent... Right?

One important reason I use premium sometimes is.......

No ethanol !

Some stations in some areas (central/Northern WI, MN, SD) have premium marked NO ETHANOL.
Ethanol of course kills mileage and is corrosive (it's legislated into most blends of gas basically for political reasons)

Plenty of articles about this in our eco section and all over the internet for those who are not up to speed about ethanol.

Actually, ethanol is used in many places to increase octane....

Yes it is, and many folks with highly tuned turbocharged and supercharged engines run E85 precisely for this reason. However the energy content of ethanol is less than gasoline, so MPG suffers.

It would be interesting to compare the timing advance with E10 and "pure" gas in a Fit. But speaking for myself I'd still rather have "pure" gas back again and get my MPG back where it used to be.

Yes there is one negative, you wasted a couple of bucks for a car that doesn't require a high octane gas.

Yep, before GM pulled the plug on SAAB, they were getting into this with their "EcoBoost" concepts. They were flexfuel turbos that made more hp with e85 than regular gas. Of course, in the newest generation Ecotecs turbos they were using, I believe regular 87 was all that was spec'd. So I wonder if just putting in premium would have had a similar effect?