I asked my engine builder (Nicholsen Mclaren) if they had observed any patterns regarding engine oil types and got an uninterested “no”.
Same here, look my oil analysis in the other thread … almost perfect now with W100 plus Camguard and much better than a year ago when i flew 15/50 without Camguard. It really seems to be the only additive that works.
(Now I also bought an engine heater, more this afternoon after i did some pictures)
Sticking Valve and Synthetic Oil
I read recently in the book “Fly the Engine” that the primary cause of sticking valve is dirty oil cooking between valve guide and valve stem. Since synthetic oil is more stable at higher temperatures, the conclusion is that engine oils blended with synthetic oil, like Exxon Elite, should be preferred over pure mineral oils, if sticking valve is a concern. Makes sense to me. Opinions?
Exxon Elite is not synthetic oil. I vaguely recall synthetic oils were tried some years ago and resulted in many damaged engines and lots of compensation.
My high oil loss issue was not AFAIK related to valves, but to bunged up oil ring(s). My oil loss is now stable around 3-4hrs per quart.
Peter wrote:
Exxon Elite is not synthetic oil.
Yes, but 25% is synthetic, perhaps enough to make a difference in terms of temperature stability.
Aeroshell 15W/50 is also semi-synthetic
You may have a point about semi synthetic oils being less likely to jam valve guides but I don’t recall reading such a finding, and I would have expected it to be well known in the big US community.
Also valve guide jamming is much less common with the chrome plated guides (the cylinders marked with “C”) which have been around since about year 2000, so the population of affected engines will be reducing.
The wider question of multigrade versus single grade has been discussed too. The conclusion, to the extent that one can be reached, seems to be that single grade plus Camguard is the best, because the multigrades contain additives which are undesirable (Exxon Elite causes watery sludge – I can vouch for that very much – and Shell 15W/50 damages seals in the engine, according to an oil specialist who has occassionally posted here). But if you have to deal with big ground temperature variations then multigrade may be necessary to start the engine, and his advice was to use 50/50 15W/50 and W80 (plus Camguard).
Is there evidence that aeroshell 15/50 which is 50% synthetic is less likely to result in sticking values.
I’ve had 3 sticking values in ,o-200 over something like 4000 hours. One of the aircraft was run on aeroshell the other two monograde.
I also know off a C150 that did 1500 hours over about 18 months all on UL91. It had done about 500 hours of avgas before that. I was certain that over time this aircraft engine all stayed alot cleaner and it never had lead fouling problems. Howver it did need one cylinder replacing as it lost compression. That aircraft ran on monograde.
Also as you alluded I’m another one of your post how effective are the cleaning/washing/dispercent agent in modern (read ancient) aircraft oils.
A good example was the tb20 with excessive oil loss/consumption written about on these forums. That was using dispercent oil (and I think the oil was replaced every 25 hours). Yet one assumes deposits still built up with this oil. Onecalso assumes the additives in mobil one (0w-20w) cleans much better. As the spark plug pictures were quite remarkable.
A good example was the tb20 with excessive oil loss/consumption written about on these forums. That was using dispercent oil (and I think the oil was replaced every 25 hours). Yet one assumes deposits still built up with this oil. Onecalso assumes the additives in mobil one (0w-20w) cleans much better. As the spark plug pictures were quite remarkable.
Yes, although that event happened only after a close succession of high altitude (low power – probably 40%) flights. In the previous ~2k hrs the engine didn’t have a problem. The conclusion seems to be that these engines don’t like running at low power for too long. You have to do higher power flights in between.
The problem with motor oils (0W20 etc) is that they can lead to metallic deposits in the combustion chamber which can cause pre-ignition. From what I heard, this takes some tens of hours, so the motor oil solution to clean the engine is suitable for short periods only, say 5-10hrs before a service.
In thirty or so years in the business I have yet to see a stuck valve in a high chrome guide fitted to a fixed wing aircraft, most valve sticking is down to very old valve guides and /or very high oil temp for long periods of time.
Sticking valves is largely a helicopter problem, the machines work at high power for long periods especially when training.
