I use 85, due to altitude, same as 87 at sealevel. And when i have run premium my mileage was less. Go figure

 

Engineer you may be, but an economist you ain't. That is misleading math you're doing there. What you want to determine is dollars per mile.

$per gallon, $2.49: divided by miles/gallon, 32: equals $0.078 per mile
$per gallon, $2.69: divided by miles/gallon, 34: equals $0.079 per mile

Not much difference -- or is it? Let's toss some miles in there so the numbers get bigger.

10,000 miles at $0.078 per mile equals $778.13
10,000 miles at $0.079 per mile equals $791.18

Still not much difference. The fact of the matter is that the cost of gasoline is a relatively small portion of the total cost per mile to drive a car. By far, depreciation is the greatest cost, followed by fixed costs such as insurance and maintenance. Next comes gas, followed very closely by interest on the car loan (if gas was $2/gallon, interest on the loan would be higher).

Bottom line: using the cost difference as a reason to use 87 octane instead of 93 octane doesn't really add up. And if you really, really want to save money on driving, buy old cars that don't depreciate and pay for them in cash.
It's already been shown that the Fit does indeed advance timing further when burning 93 octane than it does when burning 87. However the tests were performed at WOT, so there is still some question as to the benefit of higher octane under normal driving conditions.

 

If I can get the software sorted out (working on it now), I'm gonna log some 93 octane runs today . . . Hopefully be able to get some consistent part-throttle runs in as well as WOT. Gotta find someplace to do it, though. Then I'm heading on a trip tomorrow, so I'll burn through the rest of the tank & put 87 back in. Test w/ the 87 & repeat next weekend.


I feel I should repeat, though - just because ignition timing advances with the higher octane, that doesn't necessarily mean the engine is making any more power, or running any more efficiently.

 

Yep.

You did the same math I did. Note that spending 8% more to gain 6% in mpg is a 2% loss; its is exactly the same as 778.13 vs 791.18 using your numbers. You just don't think saving a near tank's worth of refill per 10,000 miles is significant.
An economist says the $13.50 is significant because its money wasted. you didn't get your money's worth because you traveled only 12.64 miles per dollar instead of 12.85 miles.
If you were running a business thats very signicant. Again, its not the amount of difference its that you spend more than you get.
While gas is not the biggest portion of vehicle cost it is the largest of variable costs, the things I can do with my fleet that affect my costs. When I run 10 trucks at 5000 miles each per month, thats $67.50/mo (or $810 a year) I can put in profit that I wouldn't have. Add that to a hundred other things I kept careful tabs on amounted to probably $1000 per month my business didn't throw away. Or I had to charge my customers for unnecessarily. you need to sharpen your thinking on whats proper spending or I'll sic Clark Howard on you. LOL


Just where do you find the advance curves for Fits showing further advance when using premium? The ones run here shown them the same within one degree, our maximum margin of error. While there is a retarding program when spark knock is detected I find none that advances the curve when no spark knock is detected.

 

I'm looking forward to that!

Meh. 13 bucks over 10,000 miles, that's a whole year for a lot of people. If putting premium in their cars gives them greater peace of mind, then it's worth it to them. My point is, and remains, that it isn't really that significant in the grand scheme.

That said, if someone really wants to spend a little extra on gas I still strongly advocate spending it on quality 87 before discount 93. For our cars, the additives in the brand name fuels are worth far more in terms of engine longevity that a couple points of octane ever will be.
I posted the link earlier, here it is again: https://www.fitfreak.net/forums/481366-post157.html

 

Thread with all the data from my logging sessions

 

Daemione, I tried to use the Palmer download and it doesn't want to work citing Unregistered user..... I am sure that the results proved that there was some difference and probably enough to influence you to look at possibly wanting to start using 92 octane fuel or at least doing some more research before deciding not to..... I hope that there is some way for you to share your results as it is a topic that stimulates a lot of debate and is of great interest to those of us here that are pen minded.... European owners have claimed that their Fits are more powerful and get the best fuel mileage on 97octane fuel.

 

That is also true here but in Europe the cost penalty for using premium is much less economical thanks to $8 and $9 a gallon gasolines.. Its cents per mile that counts.
Octane rating and heats of combustion are not the same thing.
Honda designed the 1500 engine to use the most available gasoline around the world - 87 octane but of varying energy levels.

 

Go ahead and run it unregistered - it'll let you view log files without getting a license for it. I'm running it unregistered on my desktop, with the full version on my laptop.

 

Even if my mpg increase is zero, a 2 or 3 horsepower improvement is attractive to me. I'll somehow find room in my budget for the extra $2 once or twice a month . . .

But getting data that shows it actually results in extra power is going to be more involved. Maybe I'll check around my area for any events that might be running a dyno-day discount or something . . . run the car to almost empty on one grade of fuel, do some runs, then fill it up with the new grade & do a few more runs. And pray conditions are comparable between runs that day.

 

Before I super charged my, car I was consisitently getting 37 to 39 MPG, mostly in the mid 38 mpg area..... This is driving the speed limit, slow and easy, where there are likely to be cops and 75 to 100 mph on stretches where I feel safe..... I was able to manage 33.7 when I filled up today but I am soft pedalling most all of the time, but when I get on the boost on occasion, it really kills my mileage average.

 

Love the discussion. Keep it going.

So, is there a definite answer as to what type gas to use for most MPG?

handymus

 

I just came across this post today. We were discussing this today as I just bought a new 2015 fit. I looked in my manual, and I quote from page 21 of the manual," Fuel recommendation: Unleaded gasoline with a pump octane number 87 or higher required." The manual also mentions something about Top Tier Detergent gasoline
and that this is endorsed by Honda.

 

I just moved to a place with a lot of 85 octane all over the place. What would it do, explode my car? I haven't put it in yet. I've been going to Sam's Club and they only sell 85 and 91. 91 only costs 2.15 though and everywhere else 85 is 2.15. So what happens if I put 85 in? I'm too scared to test it.

 

Your car will explode into a Champagne Supernova In The Sky.

Or maybe not.

 

There's only one way to find out.

Seriously, I've personally have no problems.

 

I wish I knew where you are located, but 85 is normally sold in high altitude regions where lower octane is all that is needed.

 

wow all some very useful information for those that don't know the difference in the fuel type and what to use on their cars.

 

another question to add.

a shell station by me now as ethanol free 87.

what is the benefit of ethanol free vs 10% ethanol.