Autogas vs 100LL

[sonex1374]

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

[WaiexN143NM]

Hi jeff,
Thanks for a timely article. While im not a fan of auto gas, i use 100LL exclusively, its good to source a quality station. auto gas seems to sour after a month or so. 100LL lasts a long time. During this pandemic ive been keeping low fuel levels in my cars and adding stabil. any body using auto gas , and not been flying much are you adding stabil?
and speaking of additives, i always add some decalin or tcp to my 100LL. its a lead disperse agent . acs sells it , dont forget to get the nifty little syringe to get it out of can, measure, and add to fuel.
ive read some of you mix 100LL and auto fuel. that maybe better for vapor pressure and vapor lock.
fly safe!

WaiexN143NM
Michael

[tx_swordguy]

I am using non ethanol auto gas 91 octane with marvels mystery oil almost exclusively. I have my fuel lines nsulated and I use a 55 gallon barrel with a 5 micron filter. I live in north Texas where it hits 100+ from mid July on. I have not had burps or anything related to fuel issues that I know of. I fly about 80 hrs a yr so it doesn’t sit very long . I probably go through 50 gallons in a month and a half. I like the idea of not worrying about the lead. I had to pull all my heads about a yr ago and found lead deposits on the piston crowns that were a pain to get off. I may be looking at something that might not have actually happened but av gas did seem to keep the egts and maybe the chts degree or two cooler at similar settings. Even with that I prefer staying with what I am doing. The farm gas station is a mile from the hanger so why not do it.
Mark

[n502pd]

I religously use TCP in my 100ll on my aerovee, and over two years have had no lead build up to speak of. Also used it for many years in the o300 on the 172. also used, in the o300. MMO in the car gas when I could get straight mogas prior to switching back to 100ll. TCP is good for leaded fuels, but really not so good on your liver, IMHO!!

[GraemeSmith]

So just before the MMO / TCP popcorn debate gets going......

10 years ago - I was staunchly against MMO - basically Stoddard solvent and some dye. I could find no science to justify the many claims people made for how it helped their engines not get stuck valves because it stopped lead build up. Yeah - right. Maybe they just had good leaning practices? Now TCP - there is come chemistry there about turning lead to lead phosphate instead of lead metal and having the lead phosphate dust go overboard in the exhaust. All well and good (unless you are down below).

Till...........I had reason to pull the MSDS for MMO recently. And then I had to go pull an older copy of the MSDS to be sure what I saw. Hey - guess what? MMO started adding TCP to their formulation about three years ago. So there is now potentially some science to the claims MMO prevents lead build ups.

Though I still prefer the Decalin "Run Up" - TCP in its neat dispensing bottle.

[WaiexN143NM]

Hi mark,all,
Just a quick question for yourself or anyone adding mmo marvel mystery oil to their fuel. How much do you put in ?
What is the ammount or ratio you use? the tcp has instruction on back of can and the nifty syringe goes into the small
hole in cap and you draw out the desired ammount on syringe, to add in the tank.

best of health to everyone

looking forward to see everyone at airventure 2021!

WaiexN143NM
Michael

[Carlos Trigo]

So just before the MMO / TCP popcorn debate gets going......

10 years ago - I was staunchly against MMO - basically Stoddard solvent and some dye. I could find no science to justify the many claims people made for how it helped their engines not get stuck valves because it stopped lead build up. Yeah - right. Maybe they just had good leaning practices? Now TCP - there is come chemistry there about turning lead to lead phosphate instead of lead metal and having the lead phosphate dust go overboard in the exhaust. All well and good (unless you are down below).

Till...........I had reason to pull the MSDS for MMO recently. And then I had to go pull an older copy of the MSDS to be sure what I saw. Hey - guess what? MMO started adding TCP to their formulation about three years ago. So there is now potentially some science to the claims MMO prevents lead build ups.

Though I still prefer the Decalin "Run Up" - TCP in its neat dispensing bottle.

MMO, TCP, MSDS, that’s too many initials for me...

[tx_swordguy]

Michael, I use 4oz per 10 gal I believe. It is what is recommended. I make no claims other than it makes me feel better and the research I have done makes me feel it is better than doing nothing. Everyone can make there own ideas about the additives. I simply stated what I do and that it works for me. Your mileage may vary
Mark

[WaiexN143NM]

hi mark , all,
Thanks for the reply. graeme’s research showing tcp added to the mmo formula is helping the lead scavenge.
carlos:
MMO. Marvel Mystery Oil
TCP. Tricresyl Phosphate
MSDS. Material Safety Data Sheet

Graeme i’ll take some of that popcorn! thanks for all your informative posts.

WaiexN143NM
Michael

[Carlos Trigo]

Thanks Michael


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