Difference between leaded and unleaded gas?

[Toffen]

Hi!
I have a Promax 300 and reccommended fuel is 98 RON unleaded (92 posted octane unleaded). Since last year several marinas have decided not to sell this fuel in Norway, and the only fuel I can get is 98RON leaded fuel.
I can get hold of 98RON unleaded at the gas stations, but then I have to use small cans and walk some distance as well.
What is the difference between leaded and unleaded fuel? What does it mean for the engine and performance?
Cheers, Toffen - Norway

[HydroStream6]

Leaded fuel is just that, it has lead in it. The lead is added for lubrication purposes, and was popular over here in the 'States for a long time. With newer technology now though, it is unnecessary to use leaded fuel, in fact I *believe* it will actually harm your engine. I could be wrong, but I wouldn't use it.

[laster]

How would lead harm a 2 stroke motor? About the only negative I can think of is that lead does contribute to fouling of spark plugs and that is probably insignificant in an engine that burns mixed gas and oil.

[Bowman]

the problem was actually with unleaded fuel.. The lead used to provide a kind of lubrication and also used to help stop the valve seats wearing in 4 stroke motors (a kind of cushioning effect when the valve closed). that's why you'll find a lead alternative that you can add to unleaded fuel for some older motors.
As a 2 stroke doesnt have any valves its fine to use either fuel. "If anything leaded is probably better as long as the octane rating is the same or higher".
The problem with putting leaded fuel into an unleaded car is that the lead stops the catalytic converter working(2 strokes don't have catalytic converters).
As a little footnote we used to get unleaded fuel and then top up with leaded. the result is that the lead raises the octane of the unleaded even further. I used to use 70% unlead to 30% lead fuel. A kind of cheap hot mix.
[This message has been edited by Bowman (edited June 19, 2001).]
[This message has been edited by Bowman (edited June 19, 2001).]
[This message has been edited by Bowman (edited June 19, 2001).]