Hi,

wvarn1957-RCU, you are absolutely right about the valve problems. This also occurred in the automotive industry with the switch to unleaded fuels, until they came out with hardened exhaust seats and better valve materials. The lead lubricates the valve seat, and is much nicer to valves in general than unleaded fuel.

However, in the aviation engines, I have seen a lot of plug fouling problems on the older 80/87 engines when using 100LL. We often use a special vibrating tool to break up the little lead balls that foul the plugs. It usually occurs on the bottom plugs interestingly enough. As we've said, this lead could be a real problem in our model engines.

Another good point, is that many of the auto fuels available today have up to 10% alcohol already in them. We have a lot of problems with this in ultralight airplanes, as these aircraft also use two-stroke engines almost exclusively. The problem is that the alcohol, being hygroscopic, will absorb moisture right out of the air. Normally this is not problematic, but with a two stroke what happens is that the water that the alcohol absorbs will not mix with the oil in the mix. There have been a lot of ultralight airplane engine failures do to this, and we explicity warn people NOT to use gasoline with alcohol in it in their ultralight airplanes.

In light of this, I would recommend that anyone using a gasoline/alcohol mix in their model engines to mix their fuel only small batches, keep it tightly sealed to prevent water absorption, and try to determine if the fuel already has alcohol in it before adding more.

As always, other input/opinions are welcome,
AV8TOR