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Tim,
I had successfully used auto fuel for many years....UNTIL I had to let the airplace sit for a while.
I really cannot blame the problem on Auto Fuel as such; but also to my dismissal of a bad smell...which I ignored. The fuel from the filling station Amoco un- leaded...slightly smelled of deisel fuel. Amoco fuels generally smell very clean.
I thought, no problem.
But, the Coupe was then only being high speed taxied about once a week, so very little fuel was used.... As mositure accumulates in fuel tanks, I, of course always drained any moisture before every high speed taxi ..... assuring all water was removed....
BUT, after several weeks of hot , high moisture weather, on draining the sumps, I got a green mess in the water. mmmmm.. Algae ????? Deisel/ jet fuel ????
As most of you know, Jet fuel is now treated at the refinery with Prist or some other algacide, as algae grows in fuels like jet fuel/ deisel, etc.....to prevent Algae growth and contamination of the fuel system.
I took samples and sent to Amoco.... Their response was we don't approve Auto fuel for airplanes... end of message.
The transportation of fuels thru pipelines pushes one fuel type with another..... The result is a mixed section of the fuel slug. The recieving storage field takes out this slug of mixed fuel and it is re-refined. BUT, sometimes they don't get all of the mixed fuels out of the system. Generally this is not a problem, as the mixed fuel is diluted in clean fuel. BUT, I ignored the smell, and paid dearly for it.
I cleaned the tanks, dosed the system with Prist, and cleaned the CArb; and put in 100 ll.
I saw no more sump drained algae.....
BUT, when John Wright rebuilt my Coupe, last year, on inspection of the header tank, he found gobs af algae, still in the system....
So, Auto gas is not a problem, but while leaded fuel evidently kills the algae, unleaded evidently does not...especially if you get a slug of diesel/jet fuel in your tank. And once contaminated, it is very difficult to remove all algae without removing all tanks and thoroughly cleaning the entire system.
If the fuel smells like jet fuel...even remotely, I would suggest you don't use it.
As stingy as I am, on draining the contaminated fuel, I saved it and put it into two of my cars....Bad decision.....I lost both fuel guages in about a week.... Algae eats copper ! (that is why the algae is green) ...copper wireing in the fuel guages.......... New cars have sealed fuel systems, that do not allow water vapor into the tanks,...so no water, no algae problem.....but if you put it in the tank, foolishly...you have to suffer the consequences...
I now use 100 ll, tho I do recognize the potential valve sticking problem the high levels of lead can cause in these low compression engines. After all the 65/75 & 85 were all certified on 73 octane fuel.
Fly Safe - Have Fun
REgards,
Harry Francis
N93530
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