Synthetic oil?

[Sid Lambert]

I purchased an airplane that has been using synthetic oil in it for over 400 hours. I would like to switch to Aeroshell 100W *.

Since this engine has been running synthetic, is this a wise move to switch oil type mid-life?

[glenn654]

I don't know...you might pull a valve cover and check for sludge...you could try going w/ a semi-synthetic (Aeroshell 15w50) first and eventually go "au naturel".

Glenn Wilkinson

[Geico266]

The sludge will depend on the fuel used. Synthetic oils do not disburse lead. If the 400 hours were spent burning mogas you are good to go. If the PO burned 100LL you could have a real mess on your hands. Like Glenn said pull some valve covers and look for lead build up. Call the PO and see what kind of fuel he burned.

What ever oil you switch to have the oil analyzed and see where the lead levels are.

What aviation oil is 100% synthetic? I hope he was NOT using Mobile 1.

I don't want to start an oil war, but Phillips 20w-50 is all dino oil and does a great job disbursing & suspending lead. If you are burning mogas then Shell's semi synthetic 15w-50 is an excellent choice.

[Sid Lambert]

Thanks guys.

It was Mobile 1 with an aviation additive. It spent 99% of it's time running mogas so I'm not worried about the lead as much but a carborated engine produces more carbon in my experience.

I'll pull the valve covers in the morning. I will probably switch over to Areoshell 100W and do a 5 hour oil change to get as much of the crud out as I can.

Originally Posted by Geico266

The sludge will depend on the fuel used. Synthetic oils do not disburse lead. If the 400 hours were spent burning mogas you are good to go. If the PO burned 100LL you could have a real mess on your hands. Pulls some valve covers and look for lead build up. Call the PO and see what kind of fuel he burned.

What ever oil you switch to have the oil analyzed and see where the lead levels are.

What aviation oil is 100% synthetic? I hope he was NOT using Mobile 1. I don't want to start an oil war, but Phillips 20w-50 is all dino oil and does a great jon disbursing lead. If you are burning mogas then Shell's semi synthetic 15w-50 is an excellent choice.

[Geico266]

Originally Posted by Sid Lambert

Thanks guys.

It was Mobile 1 with an aviation additive. It spent 99% of it's time running mogas so I'm not worried about the lead as much but a carborated engine produces more carbon in my experience.

I'll pull the valve covers in the morning. I will probably switch over to Areoshell 100W and do a 5 hour oil change to get as much of the crud out as I can.

Sounds like a good plan. If you are going to continue to burn mogas I would (and do) stick with semi synthetics.

That's what's great about OSH. The forums they have on oil & aircooled engines are conducted by lubrication engineers from the big aircraft lube oil companies. Very informative. Those forums are worth the trip every time. I learn "new stuff" (new to me anyway, without "old school voodoo") every time I go.

Good luck, let us know what happens on the next oil change.

[rv6ejguy]

Been running Mobil 1 for almost 260 hours in my Sube burning 100LL exclusively. No lead sludge anywhere in the case or pan when I looked about 35 hours ago. I change oil about every 35 hours. While Mobil engineers say that this oil is not good for holding lead in suspension, it seems fine with frequent changes.

Aeroshell will probably work fine too.

[asav8tor]

He got away with it probably because he was using unleaded fuel. Doesn't mean no harm in 400 hours.

The subie is a close tolerance engine. Apples to Oranges.

There is a solvent action to the dino oil that is missing in pure synthetic. Fine for close tolerance engines. Not so good for wide tolerance engines. Also since close tolerance engines should burn little or no oil they can put additives in the oil that would cause problems in the combustion chamber of wide tolerance engines.

[rv6ejguy]

Actually we see plenty of TEL and lead oxide in the oil analysis on automotive engines running 100LL (race and aviation) despite their closer tolerances, plenty makes it past the rings. Some recent work on a high power 930 Porsche running above 1750 EGT on the track showed plenty of lead in the oil after less than 5 hours on the Mobil 1. No ill effects so far. Temperature and piston to wall/ ring end gap clearances seems to make little difference. I've been using Mobil 1 in race engines with 100/130 and 100LL since around 1980. Never seen anything bad happen. Many of these turbocharged engines run relatively loose tolerances because of the high thermal loads and crankshaft bending loads. They are always spotless inside at the end of the season.

If something was going to crater in this Lyco with 400 Mobil 1 hours on it, it would have happened a long time ago IMO.

Works fine if you change often and probably no need if running unleaded. If it scares you, use Aeroshell.

It's always interesting to hear comments that something won't work even though some of us have been doing it for decades. Auto engines and especially race engines have far higher camshaft ramp rates, valve spring pressures, thermal loads, bearing and pin loads than any Lycoming. Funny that Mobil 1 works fine on a 9000 rpm NASCAR engine and a 19,000 rpm F1 engine but for some reason is going to cause a 2700 rpm Lycoming to croak in a few hours. I've heard all the conjecture about it's going to dissolve bearing shells etc... Recommended by Rotax (bike oil) with unleaded fuel as well which also have air cooled jugs.

[Geico266]

Originally Posted by lcnmrv8r

Like these guys are really gonna tell you that there stuffs not the best. Or that there are no alternatives to aviation oils. There gonna give you all the data you can take because that's what they're being paid for.

I'm not saying they don't know their stuff but they do have an agenda. To sell oil. Their oil.

Wow! I never would have thought of that!

Actually, it was the Phillip's lubrication engineer that suggested using the semi synthetic if you run mogas. Phillips does not make a synthetic oil for aviation, only Shell does. Darn that Phillips lubrication engineer, he actually had the gall to use this education and knowledge of oil to recommend someone else's product. How dare he maintain ethical standards that out weigh corporate greed. What is this world coming to?

I should have know better than to respond to an oil thread.

Where is the duct tape, my head is starting to hurt.

[Sid Lambert]

Don't despair Geico266, your advice on the intended content of the thread was invaluable.

The very first engineering class I took was about ethics in engineering. I'd like to think that others paid attention in that class as well.

Thanks again.