difference between mineral aviation oil and car engine oil?

[F1Boss]

AMSOIL was developed for aircraft - ashless dispersent, with a very good set of other stuff that I cannot understand. I use this stuff - compressions on my 550 yesterday were all 78/80 except one that was 70/80. This with the orfice used on a P&W orfice setup - TCM engines are not known for good compression checks anyway. This one has 700hrs on it, and runs great. I think I'll keep it.

I took a mid-time 540 to a fellow who "tuned it up" - when opened 'er up he called me to ask what the heck kind of oil was I using - everything looked new. That particular oil had been in the engine 150hrs!

I queried an engineer at the place where the oil comes in blue plastic bottles. He said 25% auto 20-50, and the rest with their aviation oil was about the best you could do (with dino oil). I use this fella's advice - with maybe a bit more than 25% AMSOIL mixed the blue jug oil. Seems to work for me!

I ferried a Champ from Ohio to TX - it was not in the best condition - had to stop at a Wal-Mart to get some 50 wt - compressions came up a bit (easier starting) - but it certainly ran better. No elecs, so hand-propping was the norm on this one - I could feel the compressions coming up as I progressed home.

Watch out for some auto oils - they have no (or very little) zinc in those types and your lifters will wear down rather quickly; catalytic converters do not like zinc - but the lifters in most engines we use need the zinc to survive.

[swjohnsey]

"Diesel oils" have more zinc.

[bruceh]

Blackstone Labs has a podcast and this episode seems relevant.

https://www.youtube.com/watch?v=Y_6RNjAx5Ms

TL;DR, sample was contaminated with auto oil and set off all sorts of red flags.

[rv8ch]

Originally Posted by bruceh

Blackstone Labs has a podcast and this episode seems relevant.

https://www.youtube.com/watch?v=Y_6RNjAx5Ms

TL;DR, sample was contaminated with auto oil and set off all sorts of red flags.

Thanks for pointing this out, Bruce. I had not noticed this podcast on their website - very interesting!

[agent4573]

Originally Posted by lr172

Please site a reference for a non break in oil that does not contain ashless disspersents. I think you will struggle to find one that isn't a small volume fringe product or classified as a break in oil. Larry

Just because its a "mineral oil" doesn't mean it has to be used only for break-in. So I don't know what you mean by a "non break in oil". Aeroshell 100 seems to fit the bill though.

https://www.aircraftspruce.com/catal...shelloils6.php

"AeroShell Oil 100 is approved for all aviation piston engines of civil aircraft when the use of an oil not containing a dispersant additive is required; however, it should also be used during the break-in of a new aviation piston engine or those recently overhauled."

They give 2 use cases, the first being when you want a non-disperant oil, the second being break in. So does this count as a "non break in oil" to you?

[lr172]

Originally Posted by agent4573

Just because its a "mineral oil" doesn't mean it has to be used only for break-in. So I don't know what you mean by a "non break in oil". Aeroshell 100 seems to fit the bill though.

https://www.aircraftspruce.com/catal...shelloils6.php

"AeroShell Oil 100 is approved for all aviation piston engines of civil aircraft when the use of an oil not containing a dispersant additive is required; however, it should also be used during the break-in of a new aviation piston engine or those recently overhauled."

They give 2 use cases, the first being when you want a non-disperant oil, the second being break in. So does this count as a "non break in oil" to you?

according to shell:

AeroShell Oil 100 is approved for all aviation piston engines of civil aircraft when the use of an oil not containing a dispersant additive is required

Please provide a reference where lycoming requires a non disppersent oil, outside of the break in period. The quote that I provided from lycoming states the opposite - that an oil with AD's is recommended after the break in period. There is NO requirement from Lyc to use non-dispersent oils and shell only approves the oil for engines in which a non dispersent oil is required.

One can choose to use a non-AD oil, but I truly struggle to understand why anyone would. The disspersents provide a significant value add without any negative penalty. It is not my place to tell you what oil should be used, but I just can't understand why someone would not follow the manufacturers recommendation on such an expensive piece of gear.

Sludge build up on an engine running leaded fuel is a real issue and ADs help to prevent sludge build up if proper drain intervals are followed.

Larry

[agent4573]

I guess I just read the original post wrong then. It states "he mixes mineral aviation oil". I realize that 100, 100 plus and W100 plus are all technically "mineral" oil since they're made from the same base stock, but no one in aviation ever refers to 100 plus or W100 as "mineral" oil. So yes, you are correct that most people don't use "mineral" oil except for break in, but in this case, OP specifically said mineral oil, which would lead me to believe he was mixing a "break in oil" with automotive oil and using that on a daily basis.

[lr172]

Originally Posted by agent4573

I guess I just read the original post wrong then. It states "he mixes mineral aviation oil". I realize that 100, 100 plus and W100 plus are all technically "mineral" oil since they're made from the same base stock, but no one in aviation ever refers to 100 plus or W100 as "mineral" oil. So yes, you are correct that most people don't use "mineral" oil except for break in, but in this case, OP specifically said mineral oil, which would lead me to believe he was mixing a "break in oil" with automotive oil and using that on a daily basis.

In aviation, only "straight mineral oil" means no ADs. XC20W50 is a mineral oil, but also has ADs.

Lary

[erich weaver]

Originally Posted by lr172

In aviation, only "straight mineral oil" means no ADs. XC20W50 is a mineral oil, but also has ADs.

Right. The term “mineral oil” is often incorrectly used to mean oil without ADs, but in correct usage it just identifies the oil as being petroleum based as opposed to synthetic based. Also, not everyone agrees that an engine should only be broken in using straight mineral oil (no AD or other additives). Mike Busch says there is no evidence to support this and Phillips advertises their XC20W50 (with ADs) as suitable for break in.

[gasman]

Originally Posted by erich weaver

Right. The term “mineral oil” is often incorrectly used to mean oil without ADs, but in correct usage it just identifies the oil as being petroleum based as opposed to synthetic based. Also, not everyone agrees that an engine should only be broken in using straight mineral oil (no AD or other additives). Mike Busch says there is no evidence to support this and Phillips advertises their XC20W50 (with ADs) as suitable for break in.

I used this for two break in's and each used less than a quart in 25 hours.