pre mix

[therex]

sorry to bring this back but im using Pennzoil and doing about a 100:1 ratio, if i put too much will i get worse gas mileage? and is that the best ratio to be using?

[RETed]

If you use too much, the immediate effect is that you'd get significant smoking out the exhaust.

Keep doing it and it'll foul the spark plugs, so all effects with fouled spark plugs are in effect.
Short answer - yes, this can affect gas mileage.
If you're worried about fouling, check your spark plugs every few hundred miles.


-Ted