Pick: 93 octane with ethanol, or 91 octane ethanol free?
 

local gas stations sell 93 octane 10% ethanol, which is what I normally run in my '98. One gas station sells 91 octane ethanol-free gas.

If it were 93 octane ethanol-free, it'd be a no-brainier to choose that.

What's the collective wisdom on choosing 93 octane with ethanol vs 91 octane ethanol-free gas?

I would use the 91 NON ethanol...JMHO

Are you stock or modded? If you are stock, running the 91 would be my preference. If you are modded and tuned, run ethanol with Stabil 360. It's supposed to be good and I'm using it but have no empirical evidence to support my thinking.

As long as you are driving your car and not storing it there is nothing wrong with the 93 the problems start when it sits and draws moisture

I would run the octane requirement in the owners manual, unless you want it pulling timing all the time. You may not hear it, but when I did my stock dyno's it was very evident when the knock sensors pulled timing.

:iagree:

The main difference is water. With the non-ethanol fuel, water will separate in the tank (if water gets in there) and will sink to the bottom of the tank where most pickups are. The ethanol contains more alcohol which does not allow the water to separate. Here's a clip from Youtube.
This is a little off topic but I noticed here in CA the gas prices yesterday shot up $1.00 per gallon. 93 Octane here is $4.69

If you use the 93 ETHANOL put in a bottle of Techron when you fill up every now and then...


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Ethanol 92 or 93. I have seen a lot of spark retard with the non oxy diehards. Less power potential. I believe the higher price & "off road use" has it sitting around in tanks longer. C5 fuels systems don't care, plastic tanks, lines. Even fresh 91-93 can equate to significant HP differences in forced induction or hi CR builds.

I'm using 91 non ethanol in both my 91 Mustang GT and 98 C5 and all small engine equipment and it seems their running smoother.

I just watched the video that was posted above, and it's both informative, yet a bit confusing. The "author" states that water will separate out of the non-ethanol gas, which as we all know, was an occasional problem for those of us who drive in the winter, as the water can "freeze up" a fuel line.

Then, the video goes on to show how the gas with ethanol keeps any moisture in suspension. However, at the end, the author says that ethanol content gas will draw moisture "over time", therefore it creates issues with engines that aren't used regularly, such as lawn mowers, snow blowers, etc.

It seems that the conclusions, if any, are mixed, at best.....And consider for how many decades, gas didn't have an ethanol content, and worked pretty well.

:willy: :willy:

Ethanol is hydrophilic; it will absorb moisture in the air. Gasoline is hydrophobic; water will not dissolve in it. Water gets into gas tanks by condensation (i.e., when air trapped in a gas tank is cooled below its dew point water, condenses out and sinks to the bottom of the tank.)

When I run 91 pure gas it seems to run better. However, I have only found 93 with ethanol here in northwest florida. I wonder if it is bad to switch them back and forth. I would rather run the 91 pure gas, for it seemed to run better. No technical stuff here, just the feel of the road.

I run the 91 octane "non-eth" whenever possible, but when I don't have the time to drive to the "closest" station that sells it, I use 93 octane with 10% eth, and add Lucas Oil's "ethanol antidote". I haven't had any issues.

Sorry to be quoting myself, but just an interesting side on ethanol: it's because ethanol is hydrophilic that you can't buy grain spirits at the liquor store that's stronger than 190 proof (95% alcohol by volume). Ethanol will freely absorb moisture from the air until it contains 5% water in solution. To get ethanol purer than that it would have to be distilled and bottled in a moisture-free, airtight environment. But as soon as you open the bottle, it would be on its way from 200 proof to 190 proof.

Seeing as I live in an "oil" state, I'm probably biased against the ethanol. Before I did all the mods to my car and while it was still in its stock configuration, I took my 98 Vette on a trip from OKC to Detroit to see my sons and grandkids. I always use 91 Premium no-ethanol here locally and always thought my car pulled hard. On the trip, I got 29.5mpg on the first tankful (my local 91 no-ethanol gas), then about 27mpg after that as I could only use 93 Premium w/10% ethanol the rest of the trip (that's all I could locate anyway). The car had a noticeable loss of power and less gas mileage. When I got home and started using 91 Premium non-ethanol, the car's power returned as did the gas mileage. So guess which one I use and recommend?

If you live in an Ethanol only state make sure your O2's have been replaced in the past 6 yrs of so. GM found that the original O2's used in the C5 did not stand up well to continued use of ethanol so made changes in the requirements prior to 2010. One tuner, who was part of the c5 software development team 20 yrs ago, was surprised at the results he found when he replaced his O2's recently and ran a scan log. Ended up retuning his own C5 again.

Interesting info!!


:thumbs: :thumbs: