Oil color changes quickly - need advice

A

Airplane101

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Engine oil on this O360-A4M turns color within the first few hours. It was last overhauled 24yrs ago and has 550SMOH. When I took possession of it in 2020, it had about 300SMOH, but since then, I’ve put about 250hrs on it, so I fly it regularly, compared to the previous owner who barely put 10hrs a year on it. Compressions are in the 70’s and it burns about 1qt every 12hrs and runs like a sewing machine.

Is this typical, or should I be concerned that it turns color within a few hours after an oil change and becomes opaque enough that I can’t see the markings on the dipstick?
 
Airplane101 said:
Is this typical, or should I be concerned that it turns color within a few hours after an oil change and becomes opaque enough that I can’t see the markings on the dipstick?
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Has it been doing this since you bought the aircraft 2 years ago? Regardless, its typical for your oil to turn darker as it works to lubricate and "clean" your engine while operating. However, different oils turn darker at different rates which is further dependent on the engine they run in. But so long as your compressions are good and oil consumption is within limits the oil will continue to do its job even if it turns black.
 
Does the engine have an oil screen or a spin-on filter? Screens let much carbon accumulate in the oil, and some of this stuff settles out in the sump and doesn't drain, and ends up coloring the oil sooner. The oil remaining in the galleries will also darken it.

Oil draining should be done immediately after a runup. It gets some of that stuff up in the oil so it will leave with it.
 
Most oils will turn darker when heated. Hot cylinder heads will heat the oil even if the Oil Cooler later does its job.

Water seems to give a green color to oil.


You can put a sample on tissue and hold up to light to determine if color change is from contamination or heat.
 
If running great, low oil usage, good compressions, I’d keep flying it, might get a boroscope at annual. I had similar symptoms on my 0 360 and put a thousand hours on it till I finally overhauled it. Each engine is unique.
 
Dan Thomas said:
Does the engine have an oil screen or a spin-on filter? Screens let much carbon accumulate in the oil, and some of this stuff settles out in the sump and doesn't drain, and ends up coloring the oil sooner. The oil remaining in the galleries will also darken it.

Oil draining should be done immediately after a runup. It gets some of that stuff up in the oil so it will leave with it.
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As far as I know, just a spin-on filter. Do O360A4M’s have a screen too?
 
Airplane101 said:
As far as I know, just a spin-on filter. Do O360A4M’s have a screen too?
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You'll also have a suction screen. But hes talking about where the filter is. You either have a screen or a filter.
Screenshot_20221203-163401.png
 
Airplane101 said:
How often does the suction screen need to be cleaned? I’m honestly not sure it has been.

I have a spin on filter in that case.
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Suction screen should just pick up the big parts. Not really something that needs cleaning, but rather checked at annual. In my dad's io540 it's how they found a thumbnail size chunk from the accessory case that had broken off. Everything else was stellar. Until they pulled the screen. Off to Divco the case went.
 
I am familiar with a twin diesel motor yacht with, at the time, 5000 hours on the GM 6V-53 engines. The oil would turn coal black after an hour or so of an oil change.

-Skip
 
24 years and 550 SMOH. I would wonder what the compression numbers look like, and what the cylinder walls look like through a borescope. If a previous owner was ground-running it, or just making short flights, the resulting accumulated case moisture causes corrosion that could be allowing a lot of blowby, and blowby will darken oil real quick.

I saw it too often.
 
Dan Thomas said:
24 years and 550 SMOH. I would wonder what the compression numbers look like, and what the cylinder walls look like through a borescope. If a previous owner was ground-running it, or just making short flights, the resulting accumulated case moisture causes corrosion that could be allowing a lot of blowby, and blowby will darken oil real quick.

I saw it too often.
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As of the last annual, compressions were, 72, 74, 76, 73.
 
Dan Thomas said:
24 years and 550 SMOH. I would wonder what the compression numbers look like, and what the cylinder walls look like through a borescope. If a previous owner was ground-running it, or just making short flights, the resulting accumulated case moisture causes corrosion that could be allowing a lot of blowby, and blowby will darken oil real quick.

I saw it too often.
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With blow by wouldn't you expect to be losing/burning more oil than a quart per 12 hours?
 
It can also be the cause is not with the engine itself. High localized cylinder temps that are not really reflected in the total oil temp can be the problem.

Poor fitting inter cylinder metal baffles and especially the “ boxes” at the rear of number 1 & 2 should be checked for distortion. If the baffles do not fit tight and direct air through the fins rather than around you will have hot spots.

In #4 I mentioned a method to check for contamination. If the oil is actually getting dirty there are a couple things you can have done. Consider having the Sump and Oil Cooler flushed. This is not something done with the engine running.

Suggest you have your Tech address these items at the next oil change or inspection.
 
black oil makes it easier to read the dipstick.

There are likely more pressing priorities than coordinating the colors within your engine case.
 
I’m surprised nobody has asked what kind of cylinders are on it yet.
 
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