Choosing the right fuel will protect your classic


Is it better to buy high-octane fuel with some ethanol or lower-octane fuel with none? What percentage of ethanol is too much for my old cars? George Malone, Azalia, Michigan

This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2018/08/13/choosing-the-right-fuel-for-your-classic


I own a 1968 Camaro rs with a 327. I go to our local airport and buy gas for it. It is 100 octane leaded. Yes it cost a little more but well worth it. No pings. No knocks. Turn the key a fires right up. And runs like a champ


I have an old Mustang with an inline 6. In ND I buy Premium at the pump, as it is the only non-ethanol fuel available. I don’t need the octane, but the engine doesn’t like any ethanol!


I have worked in the aircraft engine overhead field for 30 years. I have used 100/100LL in all my lawnmowers, motorcycles, outboards, quads, '63 Willies Jeep, '58 Vette, chainsaws, weedwackers, blowers, snow blowers, you name it, everything that doesn’t have a catalytic converter in it or on it.
I have never had a fuel related issue thanks to Avgas. The properties in Avgas additives tend to promote fuel stability and its dry-gas property eliminates water in the fuel system. I find the cost of fuel offsets the lack of costs for carb rebuilds, tank flushing, and replacing all rubber related components. I highly recommend it!


We have a simple rule. ANYTHING we own that has a carburetor gets ONLY non-ethanol gas.


I did not know you could pull into an airport fueling location and fill up with AVGAS. From my flying days there was a sign that I remember saying not to be used as a automotive fuel because the gas taxes have not been paid. That was many years ago. Have things changed?


I disagree. I have been using E10 for over 20 years in all my vehicles and small engines. I have never had any problems. I am going to convert my 79 Camaro to E85 very soon. Much cheaper than buying premium fuel and octane booster. Saying ethanol is bad is a myth.


Well, I sure hope that pump isn’t Diesel…green handles often are.

Choosing the correct fuel Indeed.

…right ?


Ethanol in gasoline is evil and the work of the devil. Back in the 70’s, I had a 60 Corvette that I used to feed Arco gas. The car ran “ok” until one day I put in Shell SU 2000. As I pulled away from the Shell station, the car felt as if somebody had put in a new motor. I couldn’t believe the difference. Later on I discovered that Arco gas had ethanol in it while SU2000 did not. This was before the days when they had to label the pumps with ethanol content so I didn’t know Arco slipped ethanol in the gas – those sneaky devils. Unfortunately nowadays, all the gas stations in the Chicago market (except for Speedway racing fuel) have ethanol. To dilute the ethanol, I now put in a mixture of Speedway racing gas and Shell regular.


Ethanol is very bad for engines of any type. It is not a myth. As an engine rebuilder for over 35 years, I can tell you the damage caused by burning ethanol fuel is real. Ethanol fuel is cheap for one reason,governemnt subsidies. Without it, it would cost more than non ethanol gas.


Isn’t using aviation gas in a street car illegal? Years ago, I tried to buy it for my 912 and was refused.

I use EtOH free gas in all of my pre-1990 cars. They just were not designed for it. Why take chances? I’m lucky enough to have a station that sells it nearby, and I’m sure the higher price is offset by avoiding repairs.


Remember too that 100LL avgas is not 100 octane the way octane is calculated for automotive fuel. Remember seeing (R+M)/2 at the gas station? Avgas only uses the R measurement. Converted to the (R+M)/2, Avgas would be around 96. Not a problem if that’s all your car needs, but if you need 100, you’d be a few octane numbers short.


You are correct! The government doesn’t want to loose any road tax! You can not pull your car, your motorcycle, your boat, your trailer full of gas using equipment into an airport fueling station. It is against the law to fuel any vehicles without a “N” number. Most airports will allow you to fill gas cans for your ultralight aircrafts, which are kept at a remote location.

  1. I drive a 1955 Thunderbird and I used to have a hard starting problem after driving on a hot day, until I started using 100% gasoline. The fuel costs more, but since there isn’t any ethanol in the fuel it doesn’t evaporate like the fuels that have ethanol in them. I am fortunate that there two gas stations that sell 90 octane, 100% gasoline within five miles from where I live.

1955 Thunderbird Blue


Around here (SO FL) we have many marinas, so ethanol-free gas is easy to get. The issue is that, locally anyway, it is all 90 octane, which is a bit low. Elsewhere in the state they sell 93 octane at some marinas. I use a mix of 90 ethanol-free and 103 VP ethanol-free. The issue is that the VP is now 11.50/gallon, so it is a bit much for constant driving.

As I look for a vintage “daily driver” these days, I am always thinking about the gas situation. Not sure what I will do, but it is clearly an issue unless your vintage car has been totally updated for ethanol.


I share your thoughts @lylefisher11. I have been burning E10 for years in my classic air-cooled cars and motorcycles. It has never caused significant issues, a little hard starting in heat- maybe- but overall it has never caused damage.

I feel that so long as the car is driven regularly and the gas is treated with an appropriate stabilizer prior to any storage, it will be mainly trouble free.


I find this article rather misleading for those of us that drive cars from the teens to the forties with original engines. Engines of that era are low compression engines that are designed to run on fuel with very low octane as compared to today. An engine that is run on even 87 octane that is designed to run on 40-60 octane needs to have the timing advanced 5-10° to run right and develop the power that it’s supposed to. Also, advancing the timing helps keep from burning up the exhaust valves.

So now you throw ethanol into the mix… ugh!! Many of us choose 93 octane premium fuel to get away from the ethanol, but that is going the wrong direction in the octane world since it’s hard to get the 87 fuel to burn at the right time to begin with. AV fuel has lots of wonderful properties but is even higher octane which is worse yet… for 60+ year old engines.

So there is quite the dilemma as what fuel to run for older low compression engines. Does one deal with the problems of ethanol or the problems of high octane? If you’re lucky like me, I have a gas station the sells only pure gasoline close to my car stash. So if I drive within a 100 mile radius of home I have no dilemma. The problem I have is that I frequently drive my old iron out of that 100 mile radius. I could carry extra fuel in a gas can, but I’m not crazy about having fuel strapped to the running boards. I’d rather be sitting on it. So I often have to choose between ethanol or high octane. In the end, I cringe and choose the ethanol when force to choose.


I replied with my points and my reply hasn’t appeared. Discobot said it wasn’t bookmarked and that was apparently a problem. Maybe it takes awhile to be screened before published.

It is interesting to hear everyone’s points. My vote is I disagree ethanol is bad for gasoline ICEs and their systems contributing water to the “mix”. Just thought I’d try putting in again my $0.02 again.


I have had 5 old British cars and two old Corvettes… NONE of them EVER got Ethanol. We also buy non-ethanol 91 for our small engines: mowers, blowers, weed trimmers, etc. I also add just a tiny bit of Sea-Foam and/or Carb cleaner with each tank refill on the small engines, since that gas may sit some without use. Why should we support an industry where it costs MORE to manufacture the product AND can damage engine internals? The difference in price does not make up for the cost of repairing the damage alcohol can do. We didn’t put it in our 2015 Corvette and it’s not going in the 2018 either.


So how do those writers who claim to use AVGAS obtain it?