The International Cessna^® 170 Association

Dear Fellow Cessna 170 Members:

After hours and hours of research, after consulting with numerous trusted individuals who have been using auto fuel in the aircraft for many years, and because with av gas in my area approaching $4 per gallon, I have no choice if I wish to keep flying a reasonable numbers of hours per year, I have decided to try autogas in my 1948 170 if I can verify the following:

According to the research, auto gas is not recommended in engines that do not have "hardened valves and valvetrain components - compatible with 100LL." In addition, the articles published by EAA and others speculate that there are very few aircraft still flying with the old soft valvetrain components.

My engine was overhauled with all new cylinders, valves, pistons, rings etc. in 1990. My question to you all is, is there any way for me to determine, without having a record of the parts used, whether "hardened" valves and valvetrain components were used?

Thank you,

Curt Bogle

Also, sorry for not mentioning this, but, my plane has the auto gas STC.

Thanks,

Curt

Curt, I'm sorry to say I don't know of a simple answer for you. But a possible solution might be to include a couple of gallons of avgas in each tankful of autogas.

Curt I'm sure you have the new hardened components but you could find out for sure by talking to the manufacturer of the your new (in 1990) cylinders.

Are you sure you have that right anyway. I'd think you'd need the hardened valves and seats to use 100 octane.

Curt, stop worrying about it. Your engine will in all probability run better and cleaner on mogas than it ever did on avgas. I've been using it for twenty years or more and never had a minutes problem. My onjy caution is do not store the airplane for long periods(over four months) with mogas in the tanks. It does deteriorate when stored too long. I've never tried to determine what my valve seats or valves were made of and I don't know of anyone else that did either, and I've never known anyone that had a problem.

Guys:

Thanks for the resonses...you are right...I probably worry too much but I'd like to be one of those "old, not bold" pilots.

Also, according to the articles out on the EAA web site, the hardened valves and valvetrains were specifically intended for 100 octane gasoline, but, it turned out that they also solved some of the early problems that engines were experiencing on unleaded automotive fuel. The articles I'm referring to are in the "auto STC" section of the EAA website.

Thanks again for your feedback all, always very helpful.

Best regards,

Curt

Regarding auto gas - I have a 52 B-model and my C-145 has the STC for auto gas and it's available over in Plymouth MA. My question is - can I mix the auto gas with 100LL or do I need to use one or the other?

If you can mix them, is their a specific ratio that the C-145's seem to do better with than another?

Thanks in advance

You may mix them...in any ratio you wish. Many folks who are concerned about valve-wear recommend a 50/50 mix. (As an avgas only type, I have to mention that it makes me wonder what the real advantage of doing that is. It seems to me that by mixing them you are getting the disadvantages of both fuels while getting little or none of the advantages of either. You are either getting mogas with lead (and paying more for it in the bargain) ..... or avgas of questionable quality and composition.
Of course, mogas advocates are just as convinced that I'm nuts.)

If these engines were as well designed as the Briggs and Stratton in my John Deere lawn mower I think I might worry about it. Auto gas has given me a lot less woes over the years as far as valve problems are concerned. Use a tank of Av gas once in a while (as we all are required to do on our cross country flights) don't let it sit in your tank un-used for long periods of time, and buy Top name brands (ie. Texico, Chevron, etc.) and enjoy your flight. LEAD is our worst enemy in these low compression engines from my experience.

Joe

P.S. Tuesday I celebrated my 25th birthday as a pilot and on the 29th of this month I'll celebrate 17 wonderful years of 170 ownership. Life is Good.