I wonder if his recommendation was simply mirroring what the auto fuel STC paperwork says? As far as I know, both the EAA and Petersen STCs specify that you're supposed to run leaded fuel for the first 25 or 50 hours. I can't remember which.
When I think back to it, this was rather a more complex situation than I first remembered.
The engine was relatively low time (~25 SMOH) when I bought it, and I ran it on autogas the first year. One cylinder was leaky at the next annual. The rebuilder thought that my switching to autogas with such low hours may have contributed to the leaky valve, and recommended I fly another 50 hours on 100LL... probably more due to the OTHER cylinders involved.
The rebuilt cylinder had components that were more auto-fuel compatible, but the existing ones didn't.
Don't know if the guy was smoking opium, but his business was rebuilding cylinders and he'd been doing it for years.
In any case, the OP should consider.
1. Will running on 100LL for 50 hours hurt the engine? (no)
2. Will running on 100LL for 50 hours HELP the engine (possibly)
3. Will running on 100LL for 50 hours be too expensive (only your hairdresser knows for sure....)
In my case, with a C85 and the twenty years ago, I didn't consider the extra cost that bad. I still run 100LL in the engine for half the year, starting in the fall when the weather closes down and the airplane sits more.
Heck, my HANGAR rent is three times more than my fuel costs, even when I run 100LL....
Ron Wanttaja
