race gas, leaded or UN-leaded?

2 replies to this topic
  • ____Kurt____

Posted January 17, 2007 - 12:54 PM


i was wondering, since it says on cars and not too sure about bikes it says "UNLEADED FUEL ONLY"
would i be able to run leaded? is it better? and what are teh +'s and -'s for unleaded and leaded? thanks alot. i'd be running it in... all my bike's. not straight (too much money) but mixed with super 93 octane
thanks alot.

what one is better?

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  • Ga426owner

Posted January 17, 2007 - 01:04 PM


Great question...as a former supporter of VP U4 leaded (15.00 a gal)...until it botched up my carb,(even after draining it completely) I use C12 leaded (10.50 a gal) with a 50/50 mix with premium pump.

FYI There are a few reports from U4 users having extreme early wear on valve seals....from a very reliable source

But VP has MR-PRO4 that is unleaded. (buy is is about 25.00 a gal)So either will work fine.

  • grayracer513

Posted January 17, 2007 - 02:08 PM


If you like to read spark plugs, leaded fuel is a good thing to have, since unleaded will leave the plug insulator bone white no matter what, except for way down at the inside/bottom, where you can't really see it unless you cut the plug open.

Other than that, some believe leaded fuel helps valves live longer, but there's no real proof that it does anything to help an engine built to run unleaded. Otherwise, unleaded is notably cleaner burning, other things being equal (so don't try to compare this aspect of a leaded race fuel to an unleaded pump gas).

At one point, there was no way you could buy enough octane without going to leaded fuels, but that's no longer true, and a modern MX 4-stroke doesn't need more than a pump rated octane (R+M/2) of 91 (roughly 87 Motor, or 95 Research) anyway.

More important is that you get a fuel that is blended for the application, and not a major mismatch (like VP Red, blended for high compression, carbureted cars with long, hot intake manifolds), and delivers good performance.

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