What provides protection against oil coking turbo?
- Thread starter elsmacko
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From what I've read, group III oils leave more deposits when coked, so you should look for group IV/V synthetics. Maybe someone will jump in and confirm or deny.
The most important thing you can do to prolong your turbo life is to let it cool off before shutting the engine down after a spirited drive.
The most important thing you can do to prolong your turbo life is to let it cool off before shutting the engine down after a spirited drive.
A good turbo-timer to let it cool off before shutdown.
And/Or
Redline with its polyol ester base stocks which will stand up to the heat are great.
And/Or
Redline with its polyol ester base stocks which will stand up to the heat are great.
To add a comment...the issue is not so much to just let the turbocharger cool off but to keep feeding it oil while it is slowing down. The rotor can be turning up to near 100,000 rpm when in full boost. From there is can take several minutes to roll to a stop. The problem is that, once the engine is shut down, the bearings stop getting a flow of oil and have to run with whatever oil is left in them. Because the turbocharger is still quite hot, conventional oil will actually "cook" and leave the bearings running dry. Good synthetic oil can take the heat and be able to provide adequate lubrication until the rotor comes to a stop. Or, you can let the engine idle for perhaps 2 to 5 minutes before shutting down. I have a 1994 Volvo 940 Turbo with 199,456 miles on it and the turbocharger still spins like a top. I have had it since 48,000 and have always used Mobil 1 with 10,000+ OCI.
A good anti Oxidant or use a good oil like RL.
bruce
bruce
As someone who has two of the darn things on his car that have lasted for 140K miles I have to agree. Synthetics and cool down. Post lubing is nice too. An accumulator with an orifice will do the job.
Well my turbo is watercooled also, and I let it idle after a long or hard run. Somtimes it really defeats the purpose of driving fast, if you have to sit in your car for 5 minutes after you get there to let the turbo cool down.lol Like going to work.
"Good synthetic oil can take the heat and be able to provide adequate lubrication until the rotor comes to a stop." Well that's what my question is asking: which aspect of the oil allows it to withstand turbo oil temps? I mean will Castrol Syntec work well enough? Is redline the only one good enough?
This is my 2nd turbo. Original lasted to about 120K. Previous owner went to jiffylube every 5000 miles for his usual does of 10W40 dino...back when I bought I did not know about turbo timing (or about a turbo needing better oil maintenance). I would run it hard go home and shut it off.
Anyway, is it probably the flash temp that matter most WHEN SELECTING AN OIL THAT HELPS PREVENT TURBO COKING OIL??
Anybody really know or spend much time on this?
"Good synthetic oil can take the heat and be able to provide adequate lubrication until the rotor comes to a stop." Well that's what my question is asking: which aspect of the oil allows it to withstand turbo oil temps? I mean will Castrol Syntec work well enough? Is redline the only one good enough?
This is my 2nd turbo. Original lasted to about 120K. Previous owner went to jiffylube every 5000 miles for his usual does of 10W40 dino...back when I bought I did not know about turbo timing (or about a turbo needing better oil maintenance). I would run it hard go home and shut it off.
Anyway, is it probably the flash temp that matter most WHEN SELECTING AN OIL THAT HELPS PREVENT TURBO COKING OIL??
Anybody really know or spend much time on this?
"To add a comment...the issue is not so much to just let the turbocharger cool off but to keep feeding it oil while it is slowing down. The rotor can be turning up to near 100,000 rpm when in full boost. From there is can take several minutes to roll to a stop."
Now if I beleive this to be true then where is all the compressed air going once the engine stops and the turbo continues to spin. I would think that the turbo will go from full spool to stop in just seconds as the engine slows down from full throttle to being shut off and stopped. The oil cokes from the heat that gets transfered from the exhaust impeller through the intermediate shaft to the central support bearing. Idle the engine for a few minutes to allow the shaft and bearing to cool down -- less heat will be transfered to the oil that remains stationary in the bearing after everything stops and that oil will not be pushed beyond its OXIDATION point. It is severe OXIDATION that causes the coking.
Now if I beleive this to be true then where is all the compressed air going once the engine stops and the turbo continues to spin. I would think that the turbo will go from full spool to stop in just seconds as the engine slows down from full throttle to being shut off and stopped. The oil cokes from the heat that gets transfered from the exhaust impeller through the intermediate shaft to the central support bearing. Idle the engine for a few minutes to allow the shaft and bearing to cool down -- less heat will be transfered to the oil that remains stationary in the bearing after everything stops and that oil will not be pushed beyond its OXIDATION point. It is severe OXIDATION that causes the coking.
That was my understanding as well.
""Anyway, is it probably the flash temp that matter most WHEN SELECTING AN OIL THAT HELPS PREVENT TURBO COKING OIL??""
Answer.. "A good Anti Oxidant" but you will not know what is used so just go with RL it is proven.
bruce
Answer.. "A good Anti Oxidant" but you will not know what is used so just go with RL it is proven.
bruce
Well, a few years ago I did my own test. I took a big old cast iron frying pan and heated the thing up until it was so hot that it burned off regular vegetable oil in a few seconds. I would guess around 400 to 500 degrees F. Then I put a few of drops of different oils at different spots in the pan. Very interesting. I could see the various dino oils smoke and darken and eventually turn to a sludgy residue. Mobil 1, Royal Purple, and Amsoil smoked just a little but did not blacken or sludge. After cooling the pan, they still felt like oil. The dinos were history. Not a scientific test but it proved the point that synthetics handle the heat much better than dinos.
As has been said above, Redline Oil is the way to go with a turbo.
I have a turbo-VW dune buggy that runs on alcohol. Over the years I've tried lots of stuff and Red Line with nothing else has been the best. I have a timer on the ignition that keeps the engine running for 2 (sometimes 5) minutes after I turn the key off. After switching to Red Line I quit using the timer. In the off season when you tear stuff down the turbos always looked better with Red Line. It costs a little more but I thing is worth it.
Any true synthetic should work well with a turbo. They handle heat better. Redline, Amsoil or Royal Purple would be good choices.
My turbo's come apart for updates and rebuilds fairly regularly. As a M1 15-50 user, I can say, without a doubt that the OLD formulation kept the hot side from forming any coke at all. The turbo is always perfectly clean, with minimal wear issues. Even the oil-only cooled version I used to use never had any coke build up on the hot side.
I am not so sure about this new Group III 15-50 formulation.
Chris
I am not so sure about this new Group III 15-50 formulation.
Chris
Nothing new. This is why synth only is used in jet turbines. The new question is if group 3 oil (or the SM "regular" oils) can also do it? Anyone cares to try?
Heck for modern jets even polyol ester base stocks have trouble with coking. The PAO stuff could not hang. Only the polyol ester base stocks could. GPIII not a chance.
I'd also add Castrol Syntec 0W-30 (a.k.a., "German Castrol" or simply "GC") to that list.
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