[beatr911]

Using the engine oil and not, I haven't been able to solidly confirm a difference in fuel mileage. I just don't want to give the BTUs away though. The bike seems to run just a bit better, and it's really subjective at that. It just seems a little smoother. If there is any MPG gain it would be by the replacement of 5 oz of gasoline with the 5 oz of oil. Doing a little math, 132oz/gallon x 5 gallons=660 oz per average fill. 5oz of oil/660 oz of gas = 0.7%. At 50 mpg x 1.007=50.37 for a .37mpg increase. Well within the noise of the mpg variance of my riding cycle.

Anything more than 1oz per gallon seems too much for my bike as pre-detonation becomes noticeable in hot weather. Also, there is a slight amount of ash on the plugs at this mixture. No smoke is visible, ever.

Some old timers state that they used to add oil to gas on some engines as an upper cylinder lubricant. The Concours engines seem to never wear out so it's not an issue with my bike, but I suppose it couldn't hurt. With 5000 mile oil change intervals I use up all the oil from the 3 quart drain well before the next drain occurs.

Adding used engine oil to gasoline is unconventional and not rooted in science as far as I know. Adding used engine oil to diesel works pretty well and is an acceptable practice as I've read in several diesel forum discussions. I use 20:1 diesel and used engine oil acceptably but used ATF works really well up to 30%. This is in my Chinese diesel tractor.