I'm curious as to whether there's an improvement in either performance or gas mileage in using non-ethanol high-octane gasoline. I know it's not subject to phase separation when the car is idle for prolonged periods of time, but would like to hear about owner's experiences with it. There's a small airport near where I live that sells this gas (for planes, of course) and was wondering if it's worth paying the additional cost.

Thanks,

 

Can’t vouch for Aviation fuel but in Bahrain, we have the Formula 1 track where the local petrol station there stocks Super98. I tried it for a month and car revs were weird especially in low gear. First thing from cool was a bit scary reversing. Tended to jutter.

I thought heat in the engine would be an issue but no ill effects even on long drives but that was mainly freeway driving.

Super 98 not recommended from my side simply due to extra cost having no discernible benefits

 

Max, I once spent $$$ on sunoco racing fuel. Just wanted to see 2 things, how she'd drive with pure gasoline, and how the higher than spec'd octane would do.

Good memories. Much better gas mileage. Engine "sound" was different. More power? Yes I thought so, but then spending $10+ on each gallon is bound to induce some placebo effect.

Would I do it again if I had the money laying around? Yes, sure would.

John

 

Ethanol fuel produces about 30% LESS BTU's than pure gasoline, resulting in less power and less mileage per gallon. Auto makers have been approving up to 15% Ethanol (E15) in almost all engines not approved for E85 "Flex-Fuel" since 2001. E15 produces about 4%-5% less BTU's and gas mileage than 100% gas. Good for corn, wheat, sorghum and potato farmers, good for the environment, more expensive to operate even though it costs a little less at the pump. Less BTU's means less heat and reduced power, even though the engine's control module adjusts to try and achieve the best performance out of either fuel. Here's an excellent review and drive test: https://www.edmunds.com/fuel-economy...ison-test.html

Be sure and read the comments, then make up your own mind. I go out of my way to purchase pure gasoline as the resulting mpg and power more than make up for the difference in cost, (plus, my Cat seems to growl a little louder, too....).

 

E10 has 3% less energy, not 30%.

 

Mikey, think he said ethanol, not E10 gasoline (which is 10% ethanol so 10% of 30% is 3).

 

My aviation experience is commercial (jet engines), not general aviation (reciprocating engines), but I do know that the fuel mentioned for aircraft is 100LL (low lead), one of several grades of gasoline available for piston powered aircraft, and has been around for many decades. As far as I know, avgas is not blended with ethanol, so you're getting pure gas.
And like the name implies, it does contain lead.
I wouldn't put leaded gas of any sort into my car.

 

Greg, interesting info. Can one still purchase 100LL fuel in New Jersey?

John

 

Your catalytic converters would not like the lead.

 

You can buy 100LL at any airport that serves small aircraft, which is pretty much any airport.
But I don't know why you would, as Rob mentioned in the previous post.
It's not the correct fuel for the car.

 

And the 'low lead' name is a misnomer. It actually has a fairly high lead content and it WILL foul your plugs.

 

Oh I didn't realize it has lead. Never mind.thanks guys.

John

 

it will also ruin the catalytic converters, a very expensive prospect.

 

my home town has numerous ethanol free gas pumps, and 91 octane pure gas is what I usually buy. When traveling cross country it's too time consuming to go hunting for the non-ethanol fuel so I just buy a name brand gas, also 91 octane. sometimes a 93 octane. The mpg difference is very very slight, but it's there. In my case usually 2 mpg less with the E-10. and that's at cruising speed 74-85 mph.

Z

 

one key thing to remember with racing fuels and other non-automotive fuels is that other characteristics of the fuel are different other than octane which does not do anything of itself. these fuels might have less detergents or have special anti-foaming agents. they also are engineered to have higher energy density and different burn characteristics. this is why so many who try them feel the power at lower ranges. while this will not do any particular harm, if one decides to see how far it can go, it will not take much to exceed the limits of an engine. this is why things like forged pistons and exotic metals start to matter for modified and race applications. a manufacturer builds an engine for the most expected loads and HP generation that the design is expected to experience. consequently the XK8 engines are probably over built since much of the design is modular and finds its way into the XKR. when you push the top of the line model past its design limits it will have a shorter service life, fail more often and have a higher chance of catastrophic failure. yes, there is reserve in the design for a variety of reasons, but there is going to be more wear. let's not forget that certain additives are not good for regular automotive application, not just lead, and some necessary ones are missing. for a given volume of fuel, energy density is achieved often by leaving out certain other things. higher burn rates, commonly desired for aircraft and top fuel dragsters, lower energy density for very fast burn rate. these also have very high oxygen content and fool the sensors into thinking that one is burning lean, hence more fuel and greater chance of fuel contamination of the oil.

 

people love to buy high priced racing fuel and / or racing oils, thinking they are giving their engines extra power or extra protection. These products, if really designed for a racing environment, and not just advertising nonsense, have no place in a street driven vehicle. Besides the extra cost, they do not have the additive packages that a street driven vehicle needs. People forget, professional racing engines torn down after every race, all parts cleaned or replaced, and put back in service. I don't know any street cars that get that level of care.

 

I think the consensus here is to use only automotive gasoline in our cars and leave the other fuels for their particular applications.