Does MTBE or ethanol damage fibreglass?

Not open for further replies.
May 25, 2005
Hi everyone, my first post, so be gentle. I'm working on restoring an old 70's vintage Spanish-built motorcycle(Bultaco) that has a fibreglass fuel tank. I ran across something in my web-surfing/research that claimed that MTBE and ethanol found in some modern gasolines will wreak havoc on the fibreglass gas tanks on these old bikes. Do any of you know whether this is true?

How would one determine whether a given brand of gas contains either of these? In my limited experience gas containing ethanol was usually labeled as such at the pump, but MTBE? I've heard of it being nasty getting into ground water and such, but that's about it. I have no idea how commonly or rarely this stuff is used. Is it used pretty much everywhere or only in certain areas?

How/where to obtain gas certain to not contain this stuff? I appreciate any info any of you can provide.
The fiberglass fibers are unaffected by any fuels. The resin used to bind the fibers into a composite are.

Methanol has long been known to promote corrosion, affect certain plastics and generally cause fuel system problems in older vehicles. Ethanol is less prone to cause such problems. But some still may crop up.

MTBE is not likely to show up in your local gasoline.

Bama, not aware of either of the mentioned fuels being an issue...BUT

Methanol often contains 3% acetone (to improve mileage by a factor of 4000, return fuel to your tank as you drive etc).

Actually, it oft contains acetone (I think as a co-solvent for people who want to blend).

Acetone will mess with your fibreglass.
There probably is MTBE in your gasoline, since I don't believe Alabama is one of the states which has banned it. However, I would have a hard time believing that MTBE could be very harmful to fiberglass, since a large number of the underground storage tanks used at service stations are in fact made of fiberglass themselves.
No fiberglass tank is DOT approved for highway use. The reason is fiberglass can crush, crack and break open upon impact. That can expose your body and property to raw, combustible gasoline. And of course that can set you on fire which not what you anticipated on a nice riding day.
The new Ethanol (gasohol) fuels contain alcohol. They are mandated in many areas of the country-West and East coast particularly. Alcohol has a nasty characteristic of being able to eat away the very inside layer of all polyester resin fiberglass tanks. This inside-next-to-the-fuel layer is very thin and once it is eaten away the leaching process will end. However the leached out chemicals mix with your fuel and enter the engine. After your motorcycle remains dormant for a day or two, the resins return to a solid and does so in small carburetor passages, valve guides and other fun places. The result is your bike will run poorly or not at all.
Whether the gasoline has MTBE or ethanol probably depends on where you live. Since it's an octane booster also does all gasoline have one or the other (or maybe both)? Some years ago in New York MTBE was outlawed (groundwater contamination) and then 10% ethanol was mandated, so the only fuel I think you can get here without it is race fuel. So what ever happend with the EPA or whoever considering rescinding the ethanol requirement?
Not open for further replies.