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occasional demons wrote:

fusion210 wrote:One important factor would be the ethanol content of the gas you're using. E10 will get worse mileage than straight gasoline.

Not really true.
With a carburetor/distributor controlling the spark curve, more likely, but the PCM can make up for it.
I have used up to 4 gallons of E85, and not seen much of a difference in miles than I usually get. 2 gallons E85 to a tank seems to actually do better than straight E10. If the PCM has enough spark advance available, it is going to use it.

What I said is exactly true. The pcm CAN NOT make up for a less energy dense fuel.

If the pcm can 'make up for' less energy dense fuel, all of the current cars on the road that can switch from e85 or straight gas wouldn't have much of a change in mileage right?




~31-35% loss per gallon. It's obvious to see that there is a decrease in mpg from adding ethanol. Sure e10 won't give a 30% decrease from straight gasoline, but the example I gave clearly shows a decrease. You can't get more energy out of a fuel that has less energy.

Mileage can depend greatly on ethanol content.

fusion210

All I'm saying is that with 9.8:1 C.R. and an '02 R/T pcm, I get better mileage with 2 gallons E85 to 10 gallons 93 octane, vs any other grade E10 available. Yes my car would probably go through straight E85 like water. But that was not the original comparison. You stated E10, not E85.

My C.R. is borderline for E85 use, but I am not running straight E85, and the PCM apparently has enough advance available to start the burn sooner to make up for it. Would a standard neon PCM have enough spark advance? IDK. I can fully understand an engine with a lower C.R. doing worse on E85, even with the proper pcm for it.

Is the engine making more power from it, no. But the pcm is just making use of what tools it has available. If it can get the burn started sooner, the explosion in the combustion chamber is still happening at the optimum time/phase.

Without enough advance, the burn would start too late and the main thrust of the explosion would be too near BDC, wasting the useful part of the piston/rod assy's leverage on the crankshaft.

Paul56 wrote:I generally try to stick with one of the retailers listed at this site:

http://www.toptiergas.com/

But, on my road trip to Texas I'm not always able to find one of those nor do I want to start searching for one when I just need some gas on a long trip.

+1 Same here. I am usually filling up at Quicktrip or Phillips 66. The Shell Station is 30 cents more a gallon! I used to go to this BP station that had 93 octane, but I found out it had a higher octane rating due to higher ethanol content.
(Kansas generally has 91 octane with NO ethanol)