I can pick between two types of premium gasolines;
91 octane, no ethanol
or
94 with ethanol

Which would be the best for aggressive street driving
Plus / minus between the two

 

There is no significant performance-related reason to avoid ethanol. It’s economically silly, requiring subsidies to exist, stupidly supported by Republicans to satisfy their farm state and rich ethanol plant owners, and stupidly supported by Democrats because they incorrectly think it helps the environment. It also has some performance issues for very old vehicles, boats with fiberglass gas tanks, or small tools like chain saws or lawn mowers stored over the winter with gas in the tank. But for a car made since 1990, the only, very small problem with ethanol is that you get about 3-5% poorer gas mileage with 10% ethanol in the gas. Other than that, absolutely no issue. Power is the same, engine response is the same, risk of corrosion or water in the gas tank is the same. There is simply no reason for all the ethanol horror stories.

 

I'm on my second new Vette in under 4 years and both have drank 91 octane NON ethanol 99% of the time. I have however had to do a couple of splash and goes while traveling through the state of illinois on my way to Talladega where I had no choice but to buy chit gas.

 

I will ONLY get none E high test gas if at all possible. Around home its now easy to do. Out on a road trip I try my best to get real gas.

I had recently a 05 6spd manual a 07 Z06 and now my 15.

The difference in power and performance which I closely monitored in my Z06 showed me the truth about ethanol crap gas, I will only use ethanol gas as a last resort!

 

For many of us it is virtually impossible to find ethanol free fuel unless you want to buy it at a marina and haul it home in 5 gallon cans. I use only Top Tier Shell, BP and EXXON premium in all my cars hoping that their additives will keep my engines clean and running smooth. It is my understanding that ethanol free fuel is simply not available in a lot of states, I sure can't find it in MD. When traveling I look for it but seldom find it. Maybe some day the politicians will do the right thing and phase it out but this is unlikely.

 

If you think there is a difference in power and performance with ethanol, then you either have a very active imagination or your engine control system has a problem. Besides the 3-5% reduction in gas mileage, there is absolutely, positively, and categorically zero, zilch, nada, no difference in power and performance with 10% ethanol in gas. I say that with the dual credibility that I’m a retired chemical engineer who spent a career in refining and thus know fuels and lubes backward and forward, and second, like you, I am anti-ethanol. But I also like to keep my facts straight. I dislike ethanol in gas because it is economically stupid and does not give any environmental benefits in return for that economic stupidity. Seems to me that when you criticize it for having bad effects that it really doesn’t have, you lose credibility and thus weaken your argument.

 

I agree.

On a recent 2,500 mile road trip from Springfield, M0 to Deadwood, SD, I filled up with E10 only once. Using pure-gas.org I was able to schedule my potty breaks, lunch breaks, scenic touring, etc, so I could fill my tank with E0 Top Tier premium(and not have to go out of my way to do so).

Oh, and about the better fuel economy; I averaged 29.1 MPG for the entire trip in my C6 Z06 with the best short term MPG of 35.0. If you think that it was a fluke, I monitored my altimeter to make sure I was on a level stretch of I-29 in Iowa, and the cruise was set on 74 MPH. I radioed the 2015 C7 Z51 A8(running in touring mode) that was a couple of cars behind me, and his MPG was also 35.0 MPG for the exact same time, road, weather, and he was running E0 Top Tier.

I burn 93 Octane E0 locally, but I run 91 octane E0 when on a road trip where 93 is not available.

 

I run E-85 but we did that for performance gains. (procharged)

 

I base what I said on my 07 Z06 with ethanol the power was down. Well enough to be noticeable. The mileage was off by about 2-4MPG ( Not that I care about mileage as I'm even at age 70 a serious lead-foot)

OT I know but it backs up what I say about mileage and power. For 3 years do to the fact this is the peoples republic of NY we could not even get none E gas at Marinas (FWIW i Live on a large lake) My 350 Magnum powered (Think Corvette 350) 19 footer lost over 3 miles per hour speed and I know I was refilling the tank more often. In boat talk it takes 15HP for each mile gained over 50. That translated out to a loss of about 40-50 HP and of course mileage suffers. When we finely got none E high test back wonder of wonders I got back my 3 more top end speed & better milage.

Talking to the marina owners I personally know and many other boaters that is a fact.

Not a engineer like you but a person that has seen what he has seen in the real world and I will stand on it!--

 

I don’t have any reason to doubt your mileage statements, but I don’t see how they disagree with my posts. If you had been running E10, the 3-5% mileage reduction would mean that instead of averaging 29.1mpg, you would have averaged somewhere in the range of 27.6-28.2mpg. But your power, drivability, etc, etc, would not have been any different between E0 and E10. I don’t mind people disliking ethanol. As I’ve said many times, I don’t like it myself. But I don’t think it helps to bad mouth it as though it has this great, long, laundry list of horrid characteristics that should be avoided like the plague. It’s a dumb idea that is stupidly supported by both Republicans (to make farm state voters happy) and Democrats (to make greenies happy) and needlessly wastes a lot of taxpayer money. But besides the slight mileage reduction, it isn’t going to hurt your car.

Something else must have been going on to see a 4mpg difference. Mileage varies for any number of reasons, but the most you can support for 10% ethanol would be 5%, and even that is stretching it. On highway cruising at around 30mpg, that’s at most 1.5mpg.

As far as the boat experience, the only explanation I can think of would only apply if the boat’s engine did not have closed loop fuel injection control with oxygen sensor. All cars since 1990 have such systems, and they automatically adjust for the fact the the E10 contains a bit less energy per gallon, by injecting a bit more gas. That’s what causes mileage to drop. But since you are injecting a bit more gas, power stays the same. But if the boat did not have closed loop fuel control, it would run leaner on the E10 than on the E0. If too lean, that could cause loss of power.

So I’ll stick by my statements that in any car made since 1990, other than the 3-5% mileage drop, there is no other debit to using E10.

 

The boat had a quadrajet carbt! It was a 91 and I always kept it in a good state of tune! I'm old school and well used to working with Holly, Carter and Quadrajet carbs and engine tuning

We can agree to disagree as neither of us can convince the other!-

 

Power depends on the tune. Up until the C7, the Corvette was factory tuned(air/fuel mixture) for ethanol free gasoline. Starting with the 2014 C7, GM changed the tune(A/F) to run on E10.

Burning E10 in a car with the A/F mixture set for E0 does reduce the power, as you have noticed.

 

Actually, that’s pretty convincing to me that the lean burn issue explains your observed loss of power in the boat. Carburetors meter fuel in a fixed ratio of gallons of gas to cubic feet of air. So if the gas contains less energy per gallon as ethanol does, that means that with a carburetor, when you go from E0 to E10, the effective air to fuel ratio gets leaner even though the ratio of gallons of fuel to cubic feet of air stays the same.

For a bit of semi-worthless trivia, that effect is actually how the notion of ethanol as a “clean fuel” got started back in the 1970’s. The Colorado mountains had a problem in winter with too much CO in the atmosphere due mostly to all the wood burning fireplaces. Since all cars were carbureted back then, when you added ethanol to the gas, it made the cars run leaner, and their CO emissions went down. So for the 5 cold months of the year, they required ethanol addition, and it did in fact reduce CO emissions. Of course these days, there is no such effect for cars because the closed loop fuel injection controls mean that as the car detects that the mixture is leaner than target, it automatically injects a bit more gas. So presence or absence of ethanol in a car made since 1990 has no effect on CO or any other type of emissions. The only impact is that a bit more gas is squirted in by the injectors. But back to your boat story with the Quadrajet, it would act like a 1970’s Colorado car and run leaner on E10, quite possibly losing power.

So it sounds to me like we may have a basis for agreement after all. I’ll buy your boat story and explain it with the carburetor lean burn issue. In return, you can hopefully see that cars since 1990 would not experience that issue due to their closed loop air/fuel control that unlike carburetors, will automatically adjust for fuel having more or less energy per gallon.

 

Actually, that's not true. As explained in my reply just above, the closed loop control of any car built since 1990 automatically adjusts the air/fuel ratio to compensate for changes in the fuel's energy content. It does this by maintaining the target exhaust gas O2 content as measured by the O2 sensor. If you are running E0 and switch to E10, the exhaust gas O2 content will rise because the fuel contains less energy, so not as much O2 is needed to burn it. It will then inject a bit more fuel, raising fuel to air ratio in gallons of fuel per cubic foot of air, but keeping it constant in terms of the actual need for O2. If you are running E10 and go to E0, that sequence happens in reverse. The exhaust O2 sensor detects too little O2 in exhaust and slightly reduces the amount of fuel being injected. A fancier way of saying this is that instead of holding constant air to fuel ratio, what the modern system holds constant is stoichiometry, which is the ratio of O2 to fuel needed for perfect combustion for whatever fuel is being burned. In order to hold constant stoichiometry, the ratio of gallons of gas to cubic feet of air must vary a bit as the energy content of the fuel changes.

 

I guess we can agree on the OT boat subject but I know what happened with my Z06 and that puppy was a 07. Possibly other cars, other years might have a different out come.

 

We’ll indeed have to agree to disagree on your Vette. I can give you up to 1.5mpg for the ethanol effect, but nothing on power. In my view, any mileage difference over 1.5mpg, and any power difference at all, must have been coming from some factor other than ethanol. Perhaps the leading contender would be a lame O2 sensor which could make your car revert to the behavior like the 1970’s cars in Colorado and your boat example. Trouble with that explanation is that the software in your car’s engine computer will usually detect O2 sensor problems and set your engine’s malfunction light. But as we all know, computers aren’t any more perfect than we are. Bottom line is that I can’t give you a high confidence explanation for the Vette behavior other than I’m certain it wasn’t the ethanol. But that’s what we’re agreeing to disagree on. Cheers.

 

So I guess the answer to the original question is 94 with ethanol?

 

The rational for ethanol gets worse when you consider the natural gas required to make nitrogen fertilizer and the energy used to make the other chemicals and the fuel used by tractors required to grow corn! Then there is the fuel required to truck corn to the ethanol plants and then to transport it to where it is mixed with gasoline.

Gasoline has been transported from refineries (which tree huggers reluctantly accept are needed, just not in their state ) in very efficient pipelines to most parts of the US for many years!

 

If both of them or neither of them are top tier, then yes, go with the 94. But with the base Vette engine which is tuned for 91, there is little or no advantage to 94 over 91. So if you have the base engine, and the 91 E0 is top tier but the 94 E10 isn’t, I’d go with the 91 top tier. If you have a Z06 or ZR1 or custom tuned base engine that’s tuned for 93, the question of top tier versus top octane gets muddier.

 

And don’t forget the biggest lie of all, the notion that the corn used to make the ethanol represents a greenhouse gas offset. For that to be true, you have to assume that if the land used to grow the corn didn’t grow corn for the ethanol, it would be bare earth, with no plants, trees, grass, or even weeds growing on it to absorb CO2.