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I have gas

For whatever reason the PF4 in my C10 runs best with 89 octane ethanol free. Anything else and I get occasional random stalls. In the past 2 months, every time I put something else in it, it happens.

The engine company wants 91 octane in it, but I don't feel that 9.2:1 is high enough compression for that. Plus altitude requires less octane.
 
I tested ethanol vs non ethanol in my 40+ mpg modern car (edit: non-flex fuel) over the same route with zero change.

I have a strong suspicion that low compression engines that are near single digit mpg will be impossible to tell a difference in octane (or ethanol, etc) unless as mentioned there is knock and an ECM is retarding timing.

I generally run the cheapest 87 octane gas available (still supposedly "top tier") for both cars and K5 but will run the K5 on more expensive gas a few tanks a year when that is all I can get. It doesn't care, 10mpg off-highway is what it gets. Freeway is hard to tell, I dont drive it enough. But I do pay attention to fuel economy quite closely.

FWIW the K5 has an L31 (Vortec 350) with EFI (TPI) with 9.2:1 CR. My modern cars at 10+ CR also run on 87, but are absolutely sensitive to octane (bad/old gas).

Slowing down will make far more difference.
 
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Flex fuel vehicles make the difference very clear.
 
I can't find any place close to me that is ethanol free. I'll just run what I can afford unless the engine says otherwise. The c10 I've run generic gas and good top tier shell V power. I can't tell any difference.

The Blazer I've only run '91 but unsure if it's ever been top tier. No issues noted.

Neither engine is race or high performance 350... so..
 
The engine in my 1991 Square body is a 350 swirl port TBI, which comes stock with roughly 9.25: 1 compression. I run mid-grade gas because after doing some data logging with TunerPro I found that my knock counts where a little in the high range on 87 Octane gas (not too high, but a little). After doing some data logging with 89 Octane mid-grade gas my knock counts where right on the money where they should be with the timing is set a stock 0-degrees. I like to run Chevron as much as possible because it has Techron fuel cleaner additive in it so I do not have to add any aftermarket fuel injector cleaner to it.
 
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I got 87 arco for 3.51 today. Cheapest gas I have seen in awhile. 01 burb got 12.3
 
We’ve gone from $2.96 to $3.19 in less than a week. Hell one station I passed at 10am it was $2.94 and at 4pm it was $3.09.
 
Damn, you guys are lucky. Gas here in Nevada is about $5.35 a gallon at the cheapest.
 
I think ours is 89 or something but it’s also a solid $1 more than regular 87. Ain’t worth it for the daily’s.
 
Between about 4 stations around here I can get all 3 grades in ethanol free. The only reason I'm running ethanol free in the C10 with EFI is because it's the only option with 89 octane. Otherwise it's 87 or 91. Plus the pf4 seems to prefer it.

I only get particular about using ethanol free is the trucks that sit for months at a time.
 
Bent77 said:
Did the cam come out of an RV?
I hate that term “rv cam”
Click to expand...
"RV" and "4x4" cams just seem to be generic nomenclature for any cam grind that strongly favors low-end torque over high-rpm horsepower. I think it comes from the days when there were only a handful of grinds available for even popular engines. Your options might be stock, RV, 3/4 race, and full race. or similar.
 
Only thing I run premium in is my Harley. I run non ethanol in my boat, usually its 89 or 90 octane, and I try to remember to put an additive in my gas can used for my small 2 stroke equipment that isn't used frequently to combat the ethanol. Other than that, whatever is cheapest all the way. Then again I don't have any high performance engines at the moment.
 
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