Engine Oil

Bartman

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Posted elsewhere by Larry Vrooman, figured it was worth sharing and might get a new discussion going. :)

The issue isn't multi-grade oil, but rather synthetic versus mineral oil. Back in the day, Mobil came out with a fully synthetic oil and it was all the rage,including with some of the big round radial engine users because of the longer oil life and alleged decreased wear. What resulted were a whole lof ot engine problems and a whole lot of lawsuits.

The issue was, and remains that synthetic oil doesn't do a good job of managing plead sludge. At the time 80/87 and 100 octane red gas were gone and 100LL was the only game in town for many engines. And 100 LL still has 4 times the lead in it as 80/87. That extra lead in combination with a 100% synthetic oil caused big problems with lead sludge in engines.

The end result is that today, you won't find a fully synthetic oil. The base is a mix of synthetic and mineral oil.

That said:

- If you run 100LL then a mineral oil is still a better choice.

- Mogas STCs are common and since there is virtually no lead in unleaded gasoline, there's no issue with lead sludge no issue with a partial or even full synthetic oil.

He continued;

I'm also thinking their might be some confusion about ashless dispersant and non ashless dispersant oils. As a basic review the "W" in Aeroshell W100 and the first "W" in Aeroshell W 15W100 indicates they are ashless dispersant oils. If an aviation oil doesn't have that leading W then it is not an ashless dispersant oil.

Non ashless dispersant oils are almost always used during the first 25 hours (or until the oil consumption stabilizes) of engine or cylinder break in as it prevents a build up of varnish on the cylinder(s) that can prevent the rings from properly seating. However, once break in is complete you switch to an AD oil. (That first oil change after the switch should be done at 10 or so hours to remove all that sludge you acquired in the first 25 hours of the breakin period that didn't come loose with the non AD oil.)



Thanks again to Larry for his permission to copy his comments here.
 

Bartman

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Was also tipped off that there were some videos on youtube so here are a few. If you come across any others please post links below. Thanks!