best fuel for fiberglass tank?

Discussion in 'Old's Cool' started by stainlesscycle, Feb 15, 2011.

  1. stainlesscycle

    stainlesscycle Long timer

    Jun 6, 2008
    morgantown, wv
    both tanks are sealed (caswell), but i'm always paranoid ... i have not had a problem with caswell in fiberglass tanks yet - i have one that's been sealed for 10+ years without a problem - but there's always a first time.

    options :

    pump gas and drain tanks when not in use/leave cap off. fuel will be in tanks a day or 3 maximum.

    or c12 and drain tanks anyways, i just don't gotta be in such a hurry about it. with c12 i'll probably have to rejet.

    or avgas? i've never run it.... but supposedly there's a local place here that will let you pump up to 5 gallons into metal container. just walk right up.

    c12 = expensive - $10 - $12 gallon, gotta drain it anyways. might get some bonus hp. probably not much.
    avgas = cheaper, but i've not used it before
    regular old pump gas = cheap, gotta drain it, paranoid about fiberglass....

    is there anyone here who regularly uses a proven fuel in their fiberglass tanks?
  2. motomike14

    motomike14 Thumper Crusader

    Jan 2, 2010
    I have a caswell sealed tank (used the whole bit of the kit, sealed it twice) and have been using pump 93 gas for well over a year now. Not a single issue.

    Caswell customer servie didn't recommend any stabalizer, so when it sits, I drain the tank and the carbs. I would just stick to the high octane pump gas; BP or Shell gas has been friendly to me.
  3. Duck_Pilot

    Duck_Pilot Retired Roadracer

    Jun 13, 2007
    Denver 'Burbs, Colorado, USA.
    I'd not recommend avgas. For several years, I used 100 octane low-lead, premixed in my 2T racebikes. It was a mistake. Switching to pump premium unleaded made it run much better, and with less tendency to detonate.

    Avgas is a very "dry" burning fuel, without the additives that land-based engines need. As result, it was difficult to jet properly, because the plugs took forever to color. Premixing oil with the 2T motors likely saved them from the additional wear that would have happened in a 4T engine.

    I know the question pertained to preserving your fuel tank, and my answer thus far hasn't helped with that. I've run Sinclair premium in my Ducati GT-1000 almost exclusively since new. I've had a touch of fuel tank spreading, but nothing obviously mis-shapen or unsafe about it.

    Hope this helps.
  4. Weaverman

    Weaverman Damaged goods

    Jul 27, 2009
    Mid-Michigan USA
    The big problem with fiberglass tanks today is the ethanol in the fuel. Many boats have been forced to undergo fuel tank replacement or be scrapped due to the EPAs allowance of ethanol in our fuel. Over time, ethanol dissolves the resin leaving a leaky, softened, unrepairable mess. The resin in solution has also been known to ruin engines, causing rings and valves to stick, etc.

    Not sure of your location, but try this site. It lists fuel stations who sell "neat" gasoline. Hope this helps.

    Also, I can't comment on how well the various tank sealers resist the effects of ethanol...perhaps a call to the manufacturer of the stuff you used would be helpful.
  5. Luke

    Luke GPoET&P

    Aug 25, 2004
    Beaverton, OR
    I've let E10 gas sit in a Caswell-lined fiberglass tank for up to two months and it ran fine. The only thing special I did was run the float bowl dry before parking it. This is in a 2T trials bike. Before lining the tank, a freshly cleaned tank and carb with fresh gas would gum up in about 45 minutes of run time.
  6. JLeather

    JLeather Bike Butcherer

    Aug 15, 2010
    Caswell is the good stuff, I think you'l be fine. I would definitely drain the tank if it's going to be sitting for more than say a month. Not only should that help with the tank, but this modern crap gas breaks down so fast that I wouldn't want to leave it in there too long anyway.

    Don't forget about the fuel lines too. Old rubber doesn't like ethanol any more than fiberglass does.