What's your experience?

[Mike M]

Marvel Mystery Oil + avgas = ?????

a. solution for sticky valves
b. trouble
c. neither problem nor solution
d. other

[CarlOrton]

a

[rwanttaja]

Eons ago, I had a crusty old A&P who had gotten his start working on Constellation and DC-6es. He told me to use Marvel Mystery Oil to prevent my valves from sticking.

Haven't had a sticky valve in 30+ years of C-85 operation. So mark me with an "A" as well.

Also works great as an elephant repellent. Since I started using it, I haven't had a single elephant in my hangar.

"B" can be valid, if you use too much of it. ISTR an NTSB report where the plane's oil tank was half MMO.....

Ron Wanttaja

[1600vw]

I was told years or decades ago aviators purchased this stuff in 55 gallon drums. There must have been a reason they used this. It's a shame this reason died with these aviators. Why we need to share all we know so we can pass this down to the next generation and not make them learn all this over again.

Tony

[vaflier]

I know a crop duster who uses it in his big old radial engine daily and has for many years. He and his mechnanic swear by it. His engines usually run a long time with few problems. Never a stuck valve. He has been at it for over 30 years.

[sr2500]

At one point, Steve Bennett, formerly Great Plains Aircraft Engines, told me to use 25 % Marvel Mystery Oil with my 30 W oil in the VW.
Jerry Folkerts

[L16 Pilot]

Used at times in the fuel small amount. I forget the exact ratio (4 oz / 10 gallons?) but it's hard to figure when the tanks are either not empty or full. I don't doubt the effects are probably beneficial especially when using 100 LL in low compression engines as it probably helps scavenge some of the excess lead. My understanding is because of the light viscosity it tends to 'flash off' in the oil so it's rather short lived. To my knowledge I've never had a sticky valve in near 40 years of flying although I never used the stuff on a regular basis.

[CarlOrton]

As a follow up to my "A" response above, and to L16's comment about how much. I used it in an old O-300 in a 172H. I don't remember the ratio (it's been 10 years since I've had it...), but I just added the correct ratio after refueling. I knew how much 100LL I put in, and added the "correct" amount of MMO. Also used TCP for the lead scavenging.

[Joda]

I had a valve stick on an O-320 many years ago, and my mechanic said to put some Marvel in the gas and run it for a while before doing anything else. It worked! Freed up the valve and no problems after that. I've used it in all my airplanes ever since. (It also helps lubricate the Piper fuel selector valve in the Super Cub.) I use the 4 oz in 10 gallon formula, but sometimes I'm not all that precise.

[martymayes]

This is obviously an example of b:

https://www.ntsb.gov/_layouts/ntsb.a...02LA181&akey=1

and it's fitting as it seems to be a mystery how it got in the fuel....