Advice on Oil

I've been using Shell 15W50 year round. Good oil, I'm sure, but I find I get more oil leaks and ...it's expensive.

I have six cases of Phillips 20W50 TYPE "M". I presume the "M" means it's mineral oil.

Okay to use it in my O-320B2B? Do I need to be concerned about making a switch from 15W50 (synthetic?) to a mineral oil.

Apparently, 20W50 type M is an "ashless, NON-dispersant" oil. It is "recommended for break-in ....", but they don't say you can't use it for normal operation.

15W50 is an "ash-less, dispersant" oil. I'm not sure of the technical difference between dispersant and non-dispersant oils.

Like I say, I have six cases of the stuff and would like to use it up as long as it won't harm my engine.

Advice?

I think the only bad thing is throwing detergent or dispersant at an engine that has operated extensively on non-detergent oil. Apparently all the gunk can bust loose and clog things up.
I bet if you alternated all would be ok.

Why not mix a quart or two of the cheap oil in at every oil change? What’ll it hurt? It’ll just take longer to go thru your stash.

Find someone (or multiple someone’s) that just overhauled their engines and trade some of the 20W50 M for either 20W50 XC or Shell 15W 50. Win win for all.


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No problem using the M oil. Lots of people use straight mineral oil al the time. Just change it at 25 hrs since it's lacking the dispersants that suspend contaminants in the oil better for the filter to catch. Just opinion of course.

https://www.lycoming.com/sites/default/files/SI1014N Lubricating Oil Recommendations.pdf

The discussion in part 3 would be enough to convince me not to use straight mineral for long term.

stewartb said:

https://www.lycoming.com/sites/default/files/SI1014N Lubricating Oil Recommendations.pdf

The discussion in part 3 would be enough to convince me not to use straight mineral for long term.

Click to expand...

I agree with what is stated in part 3 with one exception. Part 3 seems to imply recommending the oil changes at 10 hour intervals. Long ago a friend bought a J-3 in which the engine started squeaking. We changed to an AD oil, the squeak stopped. However the old sludge kept washing into and filling the oil screen. The screen was checked and cleaned out in just 2 or 3 hours along with frequent oil changes. Once the screen started running clean all was good with never again an issue with the engine. My point being 2 or 3 hours is a better choice than the 10 Lycoming recommends in this scenario. The key being a clean running oil screen.