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Mixing Oils

macrafic

Well Known Member
Wondering if it is OK to mix oil brands and viscosity. Here is the situation.

I live in Minnesota. During the warmer months, I use a straight weight oil (Aeroshell W100 Plus). During the colder months, I use a multi-weight (Phillips 66 X/C 20W-50). I generally only fly 50-60 hours per year, however. So, come oil change time, I only have 25-30 hours on the oil and filter. My target is to change both at least every 50 hours. (My oil filter is a severe PIA to change!!!!!!). So, am contemplating changing the oil at 25 and only changing the filter every other time (50 hrs). And, of course, cutting the filter open and analyzing any metal, or send the filter into AvLabs and let them analyze it.

The issue is the quart of oil that remains in the filter at oil change time. This oil would mix with the 6 quarts of different brand and viscosity of oil that is added after draining the oil.

My main questions: Is there a problem with this?

BTW, if you want to comment on changing oils on a seasonal basis, I am open to thoughts. My plane is hangared, and I do NOT start the plane in the colder months without having it plugged in (heated). I can't, however, guarantee that I would have this heating capability if traveling to other cold places during the winter so, avoid any possibility of cold starts, I change the oil to (mult-viscosity) to make it as easy on the engine as possible. I also worry about running multi-viscosity in warmer places I may travel to during the summer months (Arizona, Texas, etc.). So, I change the oil to a single (and heavier) weight. Truth be told, we may travel to such places 2-3 times per year, if even that. Still, one cold start and the damage that is done to the engine... Thoughts?
 
Generally speaking, oils - unlike greases - are compatible with one another. So no need to worry about the quart in the filter.
 
Or just run the XC 20-50 year round. It works as well as the straight weight oil in the summer.

Ed Holyoke
 
+1, that's what I do and live in MN as well.

Yah, I'm in SoCal and I've been running XC for years. If it works for you guys in the real cold, it's been fine in the pretty darned hot. They've got the new version (Victory) with the anti-scuff additives in it for all the flat tappet folks.

Ed Holyoke
 
multi-vis oil +2

I'm gonna second the multi-vis oil. I use AeroShell 15w50. My 0-360 oil useage went down when I switched from W100 and didn't look back years ago. This is the age of multi-vis oils so why not take advantage of it. My 2019 honda accord uses 0-20 synthetic and uses no oil in 10,000 miles. Crazy to burn so much oil in our Lycosourus engines. But I know why being air cooled big cyl gaps and all.
Make your life easier not more complicated.
Art
 
3rd for multi weight year around. Also please keep in mind that the Lycoming states 50 hour run time or 4 months for oil change.
 
I use AeroShell 15w50. My 0-360 oil useage went down when I switched from W100 and didn't look back years ago.
Interesting... a few years ago I switched from Phillips XC 20W-50 to Aeroshell 15W-50 and my consumption went up! I?d have switched back to the Phil XC but I had 8-10 cases of the Aeroshell to run through; I had a free stash of donated oil, might as well use it...
 
Multi grade oil

Rich,

The solution is move to Texas and run Aero Shell 100 W year round. I did use Shell muti-Grade for a while, but it was a quart added every 4 hours.
 
Aeroshell 15W-50 Run in my RV for over 900 hours. Missouri I think is the location they had in mind when then developed multi grade with 2-3 month of spring and 2-3 months of fall that can vary temps greatly from one flight to the next. I flew last Wednesday after work at it was 83 F and the 2 days later on Friday morning I flew and it was 33 F.

I add one, sometimes two, quarts between oil changes that I do at 50 hour interval. That is how it was with 50 hours on the engine and still the same with 900 hours and 20 oil changes later.
 
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I'm in Phoenix and bracing myself for 110F heat in about 6 weeks. I run W100 Plus year round down here, but I have no problem adding some other brand / weight if it's laying around and all I can find. I read a Deakins or Busch article years ago that said it's no problem to mix piston aviation oil.
 
Interesting... a few years ago I switched from Phillips XC 20W-50 to Aeroshell 15W-50 and my consumption went up! I?d have switched back to the Phil XC but I had 8-10 cases of the Aeroshell to run through; I had a free stash of donated oil, might as well use it...

Fly a lot or sell some of it. All of the distilled component AV oils I?m familiar with have a shelf life of ~ three years. Check for a date stamped on the boxes. Hate for anything to go to waste unused.
 
I know that after the oil stops draining, I can lift the tail up and get another 1/4 qt. Of oil out. Not sure if it’s from filter, but another tail wheel advantage as well as being 6’3”.
 
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