Autogas vs 100LL

[Onex107]

I was browsing GA News this morning and an article came up regarding autogas use in conventional airplane engines. It's an older article (2011), but still relevant I think.

https://generalaviationnews.com/2011/08 ... -is-mogas/

One main point the author made was that autogas from most retail gas stations are of sufficient quality to meet the MOGAS standards, especially premium grade no ethanol. This is interesting, but maybe a bit misleading. I've been unofficially investigating various gas stations for years to identify possible sources of gas for my Jabiru, and I've noticed that gas stations vary from place to place and brand to brand. I've found stations that sell gas with funky smells, yellowish additives that leave a residue on the inside of the can, or various debris and sludge from bad underground tanks. Clearly sourcing autogas from a local station has other considerations not related to the basic fuel they sell. I carefully evaluate a station before deciding to buy autogas for my plane, then I periodically reinspect throughout the year to look for changes or problems.

One final item in the article also caught my interest. The author notes that user experience has shown that the lower vapor pressure inherent with autogas doesn't work well with Bendix fuel injection systems. Researching this further, you'll notice a lot of familiar best practices when using autogas with fuel injection, and it relates to keeping the fuel cool. We've previously talked about the importance of keeping the heat out of your fuel lines, and this is another situation (with different airplanes and different engines) that shows the critical importance of incorporating this into your fuel system.

Jeff

Hey Jeff, I don't mean to be picky but to be technically correct, low vapor pressure is good (100 LL), high vapor pressure is bad (car gas).
The laboratory test for vapor pressure puts a measured amount of fuel in a closed container and heats it to a standard temp. The pressure above the liquid is measured. Thus a higher pressure is caused by a fuel that begins to vaporize at a lower temp. Just saying. Vapor pressure us commonly thought of in the reverse.

[badaero]

Another thing to think about with autofuel is to use a filtering funnel. I recently spent 10 hours cleaning out filter,collator and carb bowls on an slsa... the club was not using one before this. If 90% isopropyl alcohol was available I would have flushed with that, pandemic things.
Bruce