Dear Walt,

The only difference between two and 4-stroke fuel is the lubrication content. Your 4-stroke fuels usually run a couple of percentage points lower with most in the 14% - 16% range while most 2-stroke fuels run in the 18% - 20% range. As such, you would not want to run 4-stroke fuel in a 2-stroke engine, but it would be okay to run 2-stroke fuel in a 4-stroke. Actually, many of the 4-stroke engine manufacturers are now recommending no less than 18% oil content in the 4-strokes. Although the 4-strokes do seem to run smoother with less oil content, a lean run can do permanent damage.

Good flying

Clarence Lee