Oil Consumption Question

HGeorgeC*

Hi All,

Quick Question…

1981 Seneca III TSIO-360KB’s, mid time engines with OK compressions (mid 60’s with MO of 45), Borescopes OK and no visible fluid leaks.

What is a normal oil consumption rate?? 1 qt every 4-5 hours? More? Less?

What would be an abnormal consumption rate, both Hi and Low?

Your Thoughts!

Thanks in advance!

Stay Safe, Fly Safe!

George

N8434M

planewrench

I would suggest you locate the maintenance manual for the engine, the max consumption rate will be in there. In general, for TCM engines

Oil Consumption Trend Monitoring

A formal oil consumption record should be

generated for the engine installation. If oil

consumption is more than one quart every

three hours of operation or if the oil

consumption trend has changed

substantially, conduct the differential

compression and borescope examinations

defined by sections 1 and 2 of the TopCare

Health Checklist. If the oil consumption

trend is stable and the oil consumption is less

than one quart every three hours, continue

with the TopCare Health Checkl

This from TCM top care program information. For most engines. when you start getting to 1 to 1.5 qt per hour usage, you should start looking. Your engine seems to be going in that direction. Sure compressions can be fine, BUT, cylinder choke is worn, and compressions wont tell you the status of the OIL Control piston rings. If your oil is totally black after 10 hrs, you most likely have a lot of blow by. In that case, we suggest going to more frequent oil changes. Get that crap out of the engine.

Not to mention, what oil levels you run.

Carl

empannin

Hi George,

With compressions in the 60's where is the air going? rings, intake or exhaust? Are they scoping it as well with images of the cylinder walls and valves?

Carl has some great feedback. There is also something called a ring flush that is not standard but I have seen help oil consumption and compression issues past the rings.

https://resources.savvyaviation.com/wp-content/uploads/articles_aopa/AOPA_2022-01_cylinder-rescue.pdf

Here are the details of a ring flush including the mixture. I would add you should carefully clean your spark plugs too. I have heard of people using Marvel Mystery Oil too. The general idea is to force solvent past the rings to take out carbonized gunk.

https://resources.savvyaviation.com/wp-content/uploads/savvy_pdf/savvy-oil-control-ring-solvent-flush.pdf

I would say opinions vary on the authority of an owner to do this and/or if any FAA approval is required. Talk with your mechanic!

HGeorgeC*

Thanks Carl & Eric!

Appreciate you guys taking the time to respond!

I run the AD oil right at 6 qts, this Seneca has a 8 qt Tank Capacity and running anything over 6 qts seems to just blow out.

The consumption has been running at about 3/4 to 1 full qt every 5 hours.

I’ll take a look at that TCM Manual.

Thanks again guys!

George

empannin

George, 3/4 to 1 qt every 5 hrs sounds about perfect. I top off to 7 and fill at 6 and see about the same consumption as you. Filled to 8 qts you do lose that qt quick!

The TCM spec will be a limit value probably close to a qt per hr.

griff390

George;

Yeah, the general rule for Cont and Lyc GA piston engines is anything more than 6 qts of oil just winds up on the belly of the plane. In this case, the "general rule" absolutely holds true.

There are dozens of factors that affect oil consumption. Even 2 identical engines with similar hours will consume oil at different rates.

That being said, I agree with Eric, your engine's oil consumption doesn't sound excessive. Enjoy!