Oil change method

I drain the oil on my aeroplanes cold when the weather is warm and warm when the weather is cold. Makes a great hand warmer that way when its minus 2 outside. 🙂

Generally, after draining warm oil from an engine, I refill with a cheap multigrade and run the engine for 10 to 15 mins before immediately draining that oil. As for filter changes/cleaning, I only do this after the second draining.

I don’t bother doing this with my auto engines but have always used this technique of draining and flushing on all the aircraft I have owned, even the VW conversions.

I’ve used Aeroshell multigrade as the oil of choice in Lycoming and Continental engines, as this oil has very good corrosion inhibiting additives for when an engine may not be run so often through the winter months, particularly when tied down outside.

As for the “flushng oil”, I don’t waste it. It goes in the ride-on mower or anything else that runs quite happily on the “cheap stuff”!

Even the old oil gets used in a burner or chain saw (for chain lub), so nothing goes to waste.

I put a big cross with masking tape on the windscreen :). And write on it “no oil”

Yes Tony agreed. I have held an LAME licence for 51 years, starting with DC3s and P&W 1830s and am still at it with Gipsy, Cirrus, Lyc and Cont. I always drain hot whilst doing the leakdowns. (Handy hint. Wipe the dipstick and put it across the throttle quadrant. Prevents someone running the engine without putting oil back in first.)

I always drain them warmed up, the crud in the oil settles when cold, so you warm an aero engine to move it around the system and get it back into suspension, draining it cold the stuff you want to remove will still be lying in the base of the sump etc. also as the vernatherm will tend to be shut you will not be getting the stuff in the cooler and hoses back into suspension

Well, whatever your belief is on the subject, maintenance companies don’t have the time to wait for thick oil to drain on a fixed price 50 hour inspection.
Personally, I’ve never known a routine practice of cold engine oil changes or compression checks and I’ve been around aircraft for a while.
I wouldn’t consider doing that on my 20-year-old car, never mind an aero engine.

As has been stated previously, the old philosophy was to drain warm to ensure the majority of thick oil was removed from cavities and block walls, also that any debris in suspension was removed. The warmer the oil the higher chance of debris being removed from the base of the wet sump.

Modern oils are much better at flowing but it still remains, warm oil flows better than cold.

As to cost, it is like the everlasting light bulb that will most probably, never be commercially available because it will do the manufacturers and their workforce out of a job; modern oil will last a lot longer than the manufacturers/authorities change-out time.

Unfortunately we are regulated to change it at their prescribed frequency, hence the cost and keeping people in jobs (oh yes and shareholders happy as well). Cynical, who would have ever thought it! :diablo:

Run your lawn mower for a year and see how it is. Usually pretty clean. Manufacturers often prescribe change at 25-50hrs or annually whichever the soonest! Modern oil will possibly last in excess of 100hrs in a 5hp mower.
Oh well back to scalded hands.:D

Maybe it would have something to do with trying to drive any moisture out of your engine that sits on the upper surfaces of your motor esp when stood around?? The odd lycoming cam has been red labelled for such issue’s as corrosion :confused:

An oil change will never change all of the oil – hot or cold, there will always be some left in the smaller galleries and as a coating on all exposed parts.

Following various AMMs for engine overhaul / storage, etc, the correct procedure seems to be to get the engine oil hot, drain it out. Refill, run and drain. Any oil left in the galleries should be of a higher percentage of new oil.

There is an issue – it’s damned expensive and more than a bit wasteful.. unless you happen to own a Gulf State….

There is no need for an engine ” Flush ” with the latest fully synthetic motor oils . Flush warm , not hot & if you are worried maybe leave it to drain for an extra hour or so . maybe whislt you are swapping out the spark plugs !!

I remember that the general practise used to be that the oil – hot or cold – was drained and then a thinner, less viscose oil was put in the engine and circulated, the intention being to scavenge and clean out the remnants of the old original oil. This was drained and replaced by the correct grade of operating oil. This method seems to have gone out of favour.

Flushing oil was the description I was looking for !

Hi Propstrike,
I’ve tried that method a few times but I keep seizing my engines. Am I doing something wrong here? Just joking.
I do think that the modern multi-grade oils, particularly the 10/40 and the 5/30, will drain fairly easily and not require warming up. This would seem particularly so for Rotax 912 series as all that is really drained is the remote oil tank and so a lot of oil does remain in the hoses and oil cooler – for a normal drain that is.
I would hazard to suggest that the warming method is something from the old days when oil was as thick as possible and we had summer and winter single grade oils.
The question now is – do I follow my own suggested doctrine or not?
Good debate.
Richard

I’ve done it both ways depending on circumstances. If cold, I’ll always give it an hour or so to fully drain while I get on with other stuff. Multigrades seem to flow out quite well hot or cold.

Assuming that the plugs are also coming out for cleaning and gapping, then pulling the prop through a few times will get a bit more of the residual oil out too.

If you do regular compression checks at oil change time, it seems sensible to do it with consistent engine temperature either cold or warm.

How about draining it cold, then run engine for 5 mins to chase out the last of it ?:diablo:

Fascinating post.

I have some experience of doing car oil changes and have always warmed the engine before draining and suffered the odd scalded hand doing so – better now latex gloves are fashionable.

Then I moved on to 50hr checks on a CofA aircraft and again started with a warm engine.

Having just completed my first (closely supervised) annual on an LAA type I was interested to note that the draining was done from cold. I didn’t question this as the engineer / inspector who was supervising was also the engine rebuilder – he should know what he’s doing.

Thinking about it, as your post has made me do, I am guessing it’s pretty much arguable either way.

Cold, and it doesn’t flow as easily, more may be left in the sump. Warm, and as you say all the galleries etc are freshly filled.

So let’s say 5% of the old oil remains in the engine. What harm can it do?

Moggy