An Oily Question

weirdjim

weirdjim

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weirdjim
I think it is fairly safe to say that one of the main reasons we use ashless dispersant oil in our engines is to keep the particulate matter (carbon, dirt, etc.) in suspension. And, the main reason for that is that most of the pancake engines flying today don't have oil filters, just screens to catch pieces big enough to have the serial number on them intact. The idea is to keep all that crap floating around until it is time for the next oil change.

The problem is that it really doesn't all stay floating around, but some of it "plates out" into nooks and crannies where it solidifies and becomes a permanent part of the engine. Anybody who has torn an engine down at TBO or beyond knows the goop that collects on the internals of the engine and probably does no harm, but certainly doesn't do us any good.

So what if, just prior to an oil change, and without doing any flying, you were to drain the old aviation oil, put in some relatively high detergent motor oil, run the engine on the ground (perhaps even taxiing it to get the temps up), and then immediately drain the motor oil, put in the aviation oil, and then resume normal operations. The motor oil, detergent as it is, ought to have at least scavenged SOME of the crud out of the engine. Given enough time and enough oil changes, ought that engine not to be relatively clean on the inside?

Just a thought, and no, I haven't done the experiment. Advice appreciated (and not from a legality standpoint ... operationally only).

Jim
 
Aren't ashless dispersant oils considered to be detergent oils?

If crud is precipitating out of the oil, maybe the change interval needs to be shortened.


Trapper John
 
Interesting concept....

How can you be assured you'd be rid of all the "detergent"?

Doesn't some crud/film sometimes protect parts? (For example -- the engine that sits for a while between runs).
 
Every plane I've rented or owned had a filter, and not a screen. I don't know if "most" is necessarily an accurate statement.
 
weirdjim said:
I think it is fairly safe to say that one of the main reasons we use ashless dispersant oil in our engines is to keep the particulate matter (carbon, dirt, etc.) in suspension. And, the main reason for that is that most of the pancake engines flying today don't have oil filters, just screens to catch pieces big enough to have the serial number on them intact. The idea is to keep all that crap floating around until it is time for the next oil change.

keeping the particulate matter in suspension is not the purpose of a Dispersant, the ingredient is to stop sludge from forming.

The problem is that it really doesn't all stay floating around, but some of it "plates out" into nooks and crannies where it solidifies and becomes a permanent part of the engine. Anybody who has torn an engine down at TBO or beyond knows the goop that collects on the internals of the engine and probably does no harm, but certainly doesn't do us any good.

It is the best thing we have to stop corrosion, is the oil varnish that forms on steel parts.

So what if, just prior to an oil change, and without doing any flying, you were to drain the old aviation oil, put in some relatively high detergent motor oil, run the engine on the ground (perhaps even taxiing it to get the temps up), and then immediately drain the motor oil, put in the aviation oil, and then resume normal operations. The motor oil, detergent as it is, ought to have at least scavenged SOME of the crud out of the engine. Given enough time and enough oil changes, ought that engine not to be relatively clean on the inside?

It will, and it will do no harm.Airboat engines run auto oils with no problems

Just a thought, and no, I haven't done the experiment. Advice appreciated (and not from a legality standpoint ... operationally only).

Jim
Click to expand...

To help understand oil terms read oil talk for dummies at

http://www.eci.aero/pdf/BreakInInstructions.pdf#pagemode=bookmarks&page=5
 
dmccormack said:
Many airplanes have filters installed via STC. Not all.
Click to expand...

I know not all planes have filters. I wasn't even saying that more planes have filters. I was just saying that the more screens than filters statement may not necessarily be true.
 
EdFred said:
Every plane I've rented or owned had a filter, and not a screen. I don't know if "most" is necessarily an accurate statement.
Click to expand...

I'll wager every one did have a screen. It is a certification requirement, they may also have a filter.

the filter is on the pressure side of the pump, the screen is on the suction side and in ALL Lycoming Engine maintenance manuals must be removed and cleaned and checked for debris at EVERY oil change
 
dmccormack said:
Many airplanes have filters installed via STC. Not all.
Click to expand...

And many were manufactured equipped with filters and require no STC but all of them have a screen too.

It is a certification requirement to protect the oil pump from damage form large debris that would ruin the pump, and stop oil pressure.
 
Tom-D said:
I'll wager every one did have a screen. It is a certification requirement, they may also have a filter.

the filter is on the pressure side of the pump, the screen is on the suction side and in ALL Lycoming Engine maintenance manuals must be removed and cleaned and checked for debris at EVERY oil change
Click to expand...

I know mine did at one time, I've got the paperwork in the binder that says it was converted to a filter. Same with the last plane I owned. However, I don't care about 1963, I'm talking now. And NOW, whether STC'd or 337'd, or by whatever process - legal or not there are a lot of planes with filters on them. I'm not saying there are more filters out there than screens, I am just saying that the statement of "# with only screens > # with filters" is not necessarily accurate.
 
Dispersant: Suspends wear metals and contaminants in the oil until they
can be filtered or drained. Has no adverse affect on Break-In.

Note in this definition there is no mention of suspension of particulate matter.
 
Tom-D said:
Dispersant: Suspends wear metals and contaminants in the oil until they
can be filtered or drained. Has no adverse affect on Break-In.

Note in this definition there is no mention of suspension of particulate matter.
Click to expand...

Wouldn't particulate matter be considered a contaminant?


Trapper John
 
EdFred said:
I know mine did at one time, I've got the paperwork in the binder that says it was converted to a filter. Same with the last plane I owned. However, I don't care about 1963, I'm talking now. And NOW, whether STC'd or 337'd, or by whatever process - legal or not there are a lot of planes with filters on them. I'm not saying there are more filters out there than screens, I am just saying that the statement of "# with only screens > # with filters" is not necessarily accurate.
Click to expand...

the STCs that have been approved have you remove the large pressure screen, but leave the suction screen in place.

If you are flying a Lycoming the suction screen is still there even with the new STCd filter installed properly.
 
Trapper John said:
Wouldn't particulate matter be considered a contaminant?


Trapper John
Click to expand...

Yes it is, but described separately, as it has different properties than chemical contaminates.

Water, acids, and other contaminates are produced as the engine heats and breaks down the oil.
 
I ran auto engine 15W40 oil in my homebuilt's engine until I did a little research and found that auto oils will peel off some of that varnish in the engine, sometimes fast enough to plug either the suction screen or pressure screen. Took it out and resumed using aircraft engine oil. If the engine was relatively new and clean the auto engine oil might be OK, though the same research indicated that some of the metals in aircraft engines (magnesium crankcases) don't get along well with auto oils.

I wish I could find that article.

Dan
 
The Ashless requirement comes from day long gone when aircraft had bottom cylinders and top cylinders. the bottom cylinders would consume large quanities of oil and the deposits from that oil burning would leave a metal ash that would cause pre-ignition in the lower cylinders of most radials.

we long longer tolerate that kind of oil usage in our flat engines, and no longer worry about metallic ash.

but as always the FAA requirements still exist.
 
weirdjim said:
What the hell is a magnesium crankcase?

Jim
Click to expand...

It's a crankcase made of magnesium. Some of the old Continentals, IIRC, contained a bunch of it, either straight or as a magnesium-rich alloy of aluminum.

Dan
 
Dan Thomas said:
It's a crankcase made of magnesium. Some of the old Continentals, IIRC, contained a bunch of it, either straight or as a magnesium-rich alloy of aluminum.

Dan
Click to expand...

IIRC the only magnesium in any horizontally opposed aircraft engine is the occasional accessory case made of that material.
 
gismo said:
IIRC the only magnesium in any horizontally opposed aircraft engine is the occasional accessory case made of that material.
Click to expand...

The only magnesium I ever knew existed was the brake housings on Goodrich wheels in the early Cessna series. I never knew that anything was made of magnesium that would get anywhere near anything that could ignite it. DAMN but it burns bright.

Jim
 
weirdjim said:
The only magnesium I ever knew existed was the brake housings on Goodrich wheels in the early Cessna series. I never knew that anything was made of magnesium that would get anywhere near anything that could ignite it. DAMN but it burns bright.

Jim
Click to expand...

Even aluminum burns pretty good, at least in powdered form if you get it hot enough.
 
weirdjim said:
The only magnesium I ever knew existed was the brake housings on Goodrich wheels in the early Cessna series. I never knew that anything was made of magnesium that would get anywhere near anything that could ignite it. DAMN but it burns bright.

Jim
Click to expand...

C-145 and 0-300 oil sumps are mag.
 
Dan Thomas said:
It's a crankcase made of magnesium. Some of the old Continentals, IIRC, contained a bunch of it, either straight or as a magnesium-rich alloy of aluminum.

Dan
Click to expand...

Mag and aluminum can't be alloyed, the mag fumes off before the aluminum melts.
 
weirdjim said:
I think it is fairly safe to say that one of the main reasons we use ashless dispersant oil in our engines is to keep the particulate matter (carbon, dirt, etc.) in suspension. And, the main reason for that is that most of the pancake engines flying today don't have oil filters, just screens to catch pieces big enough to have the serial number on them intact. The idea is to keep all that crap floating around until it is time for the next oil change.

The problem is that it really doesn't all stay floating around, but some of it "plates out" into nooks and crannies where it solidifies and becomes a permanent part of the engine. Anybody who has torn an engine down at TBO or beyond knows the goop that collects on the internals of the engine and probably does no harm, but certainly doesn't do us any good.

So what if, just prior to an oil change, and without doing any flying, you were to drain the old aviation oil, put in some relatively high detergent motor oil, run the engine on the ground (perhaps even taxiing it to get the temps up), and then immediately drain the motor oil, put in the aviation oil, and then resume normal operations. The motor oil, detergent as it is, ought to have at least scavenged SOME of the crud out of the engine. Given enough time and enough oil changes, ought that engine not to be relatively clean on the inside?

Just a thought, and no, I haven't done the experiment. Advice appreciated (and not from a legality standpoint ... operationally only).

Jim
Click to expand...

The chemicals that keep crud in suspension are the dispersants.

Ashless doesn't mean it keeps them in suspension any better than a standard dispersant. It means they don't produce ash when burned. Ie, ashless dispersants burn completely, and don't leave additional crud in the engine.

This is important due to the compression an aviation engine will see. A car doesn't run at 100% for 5 mins and then 75% for 2 hours, so it's not as big a deal.

I've also gotten several bad reports from highly detergent oils and additives. Basically, as the engine wears, your clearances get wider, your seals move around. The crud fills in those spaces. Rinsing it away is counter to normal operations unless you're doing an overhaul.

Anyway, oil detergents don't work in a matter of 30 minutes for a warmup. In a car, you'd run it for 500 miles, then change again. That's probably 10-15 hours of engine running. I think the wear of 10-15 additional hours on an AC engine is far more expensive than the icky feeling of having a dirty engine.
 
weirdjim said:
The only magnesium I ever knew existed was the brake housings on Goodrich wheels in the early Cessna series. I never knew that anything was made of magnesium that would get anywhere near anything that could ignite it. DAMN but it burns bright.

Jim
Click to expand...

Most industrial parts made of magnesium are not 100%. I've tried igniting such things, and they don't burn. After I dug into it more, it's usually alloyed (aluminum, copper, etc) to improve strength and prevent it from being self-sustaining in a fire.
 
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