aviation fuel

[Michael W.]

Re: avation fuel

STILL HELP IS NEEDED ON WHY THE LEAKS MAY HAVE HAPPENED.

I don't think you're going to get a finite answer. No one else appears to have experienced this. Despite all of the miraculous powers that some seem to believe avgas must possess, it is not sufficiently different from pump gas to have caused the issues you noted. There is also no explanation as to why it suddenly came and went by switching fuels, with no permanent signs of damage.

Possibly the switching of fuel was just coincidental with the leaks and not really the cause.

[Domenic T.]

Re: avation fuel

Al,
let me add something to what you are asking. I have heard of the color code identification in diesel but an interesting thing about av-gas is that if you mix any 2 of their octanes it will turn clear. That was to let the one doing the pre-flight know that there may be a lesser or higher octane which lesser was not accepted, and higher had limits to it's use. The aviation octane rating went by colors starting with 3 letters: red = 3, blue=4, green=5, and purple =6, so one could tell the octane rating, red being the lowest and purple being the highest. Haven't seen the red for a while but the blue is about all that is available with the exception of some green. I use a mixture of av-gas and pump gas and have really never looked to see if the av-gas will turn clear with pump gas.
When the red was being eliminated some aircraft engines had to change their valves to use the blue. The change was mostly in the valve angle going from 30 to a 45 angle along with a timing change. The school reason was that the higher octane was not completely burned in the cylinder before it was pushed into the exhaust port. Soo now with all that, I don't think the color would get us in trouble. The first argument (long ago) was that there was no road tax on av-gas.
In 1970 when I was a Chevy mechanic, the service manager said his father had a service station and would throw red dye in the regular gas to make it look like it was premium when he ran out and pass it off as the high grade that was red at the pumps back then.
Dom

[Donald H.]

Re: avation fuel

How about a wild theory! I mentioned this to Greg. I have no background or anything to support this, but, when Greg explained his problem to me it sounded like he had NO leaks when using pump gas and all of a sudden when he switched to Av Gas he had leaks from just about every rubber O ring, hose, etc. When he switched back to pump gas, the leaks went away.

I have seen posts that some of the folk much more knowledgeable than me say that ethanol laced gas causes rubber materials to swell. So, is it possible than when the Av Gas when in and the ethanol was no longer present, all the rubber stuff shrank to a point that allowed the leaks. Then when the pump gas went back in all the rubber swelled back to seal everything.