This is not KR related, but I know there are several knowledgeable engine people on the list.
I am buying a half share of a 1962 172C with a Continental O-300 engine that has an auto fuel STC. The STC says that 87 octane can be used, but the current owner is using only 93 and also putting in 100LL every third tank. The engine has about 900 hours one it and it starts and runs great and the compression checks very good. He says that he can't tell any difference with the avgas or the auto fuel. My question is is there a reason to put in the avgas every third tank or is it better to run it just on the auto fuel except when it is away from home and only avgas is available? With our usage the plane will be fueled away from home at least one or two out of every ten tanks. Keeping up with the alternating fuel types is not that easy in a partnership. The fair way to buy fuel in a partnership is for each partner to fill it up after using it, but that can get lopsided if one partner is filling mostly with auto fuel and the other with avgas. Brian Kraut Engineering Alternatives, Inc. www.engalt.com
