Can someone give me the skinny on having motor oil coking from high temps in turbo's?Does it happen as often now as in the past?
Can u see indications in a UOA?
Thanks folks.
Nut
Can u see indications in a UOA?
Thanks folks.
Nut
Motor oil coking
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This is a great question. Hopefully somebody that knows more can offer a definative answer. In my recollection, it came only from people who shut down before letting the turbo slow down and cool off. I never shut down above 300 and try for 250. That may be why my turbo has lasted nearly 20 years.
Do as Jim does. Another good thing to do to lower EGT's is to install a larger exhaust or remove restrictive devices from exhaust systems (factory restrictive mufflers, particulate filters) and replace with quality high flow aftermarket ones (less restriction means the heat is able to escape quicker out of the exhaust). I replaced my stock setup with a Magnaflow 4" turbo-back setup w/a 3.5" down pipe. My particulate filter fell off somewhere down the road also.
Synthetic oils are also a big plus in turbo setups due to the fact that they resist burnoff more effectively in high temp. applications -vs- dino oils.
Synthetic oils are also a big plus in turbo setups due to the fact that they resist burnoff more effectively in high temp. applications -vs- dino oils.
High ester oils like RL will have a lot lower tendency if at all to cokeing compared to a PAO or GPII/GPIII based oil
bruce
bruce
Red Line is about as bullet proof of an oil that there is. It's also the only oil that I've ever run in my truck that produced high soft metal wear per UOA's. I ran it in my truck for a little over 20k miles, but the soft wear never subsided like I hoped it would so I wound up dumping it.
Yes, coking is still a real problem, probably more now than in the past. I see numerous trucks come in with failed turbos due to heat/oil problems. The new emissions engines with EGR and DPF's cats and all the rest create a lot of extra heat. On a pre "emissions" engine and a post turbo pyrometer I like to see about 250-275*F before shut down, although Airesearch and Holset tell me in most cases a little more is fine. On the newer engines with variable geometry turbos, you'll have to settle for slightly higher temps, they just run hotter.
Let it idle a bit before you shut it off and that turbo will last almost forever.
Let it idle a bit before you shut it off and that turbo will last almost forever.
It depends on several things. The turbocharger is a gas turbine driving an air compressor. The gas turbine is powered by hot exhaust gases, up to 1200°F or more at high power. The turbocharger bearings are cooled by continuously flowing engine oil.
If oil of an unsuitable quality is used, it'll coke. If the oil flow is shut off before the turbocharger bearings have cooled, it'll coke.
So, for a diesel engine, any modern oil diesel engine oil is made to work satsifactorily in turbocharged engines. If you run very hard and hot, especially if the engine is modified, I'd choose a synthetic diesel engine oil. In any case, immediately after a hot run, let the engine idle for 3-5 minutes to keep the oil flowing over the turbocharger bearings and take the heat away. Alternately, install an electric post-lube pump to do the same thing.
Ken
If oil of an unsuitable quality is used, it'll coke. If the oil flow is shut off before the turbocharger bearings have cooled, it'll coke.
So, for a diesel engine, any modern oil diesel engine oil is made to work satsifactorily in turbocharged engines. If you run very hard and hot, especially if the engine is modified, I'd choose a synthetic diesel engine oil. In any case, immediately after a hot run, let the engine idle for 3-5 minutes to keep the oil flowing over the turbocharger bearings and take the heat away. Alternately, install an electric post-lube pump to do the same thing.
Ken
thanks for the great info guys!
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