I see most alot of synthetic oil companys stating that not using a full synthetic oil in a turbocharged engine will cause "oil coking" in turbo after shutdown....this may be the case with different grade gasoline oils, but do you guru's think that petroleum HDEO's suffer from this same problem? I have yet to hear of a turbo related failure on a over the road diesel semi using the very popular rotella t 15w40.
15w40 conventional turbo coking??
- Thread starter Ponch
- Start date
- Status
Originally Posted By: Ponch
I see most alot of synthetic oil companys stating that not using a full synthetic oil in a turbocharged engine will cause "oil coking" in turbo after shutdown....this may be the case with different grade gasoline oils, but do you guru's think that petroleum HDEO's suffer from this same problem? [b]I have yet to hear of a turbo related failure on a over the road diesel semi using the very popular rotella t 15w40.[/b]
Sounds pretty accurate to me. Lots running dino without any failures for a long time.
I see most alot of synthetic oil companys stating that not using a full synthetic oil in a turbocharged engine will cause "oil coking" in turbo after shutdown....this may be the case with different grade gasoline oils, but do you guru's think that petroleum HDEO's suffer from this same problem? [b]I have yet to hear of a turbo related failure on a over the road diesel semi using the very popular rotella t 15w40.[/b]
Sounds pretty accurate to me. Lots running dino without any failures for a long time.
Last edited:
Turbos are much better designed for proper lubing these days. Oils are also much improved. I'd not worry about it. Maybe on a super long run when its really, really steaming outside let it idle for 3 to 4 minutes to cool the turbo.
JHZR2
Staff member
OTR diesels may be significantly different in turbo and lube design than consumer vehicles. I also doubt that OTR truckers instantly turn their engines off after slamming on the brake off an interstate offramp from an 80 MPH cruise.
The coking on the innards of the turbo can be an extremely slow process, and the number of hot shutdowns is a major part of this as I understand it. OTR trucks have a significantly different use profile than your typical idiot consumer.
The coking on the innards of the turbo can be an extremely slow process, and the number of hot shutdowns is a major part of this as I understand it. OTR trucks have a significantly different use profile than your typical idiot consumer.
HDEO's haven't been a problem in my Turbo.
Manufacturers assume idiot consumers when they say things like that.
The average person won't go easy on it for the last minute or 2, and let it idle for 30 seconds before shutdown to cool the turbo. They'll WOT it when cold, park it and shut it down immediately after a hard run, etc. In cases like that, synthetic will delay the inevitable turbo failure a bit.
The average person won't go easy on it for the last minute or 2, and let it idle for 30 seconds before shutdown to cool the turbo. They'll WOT it when cold, park it and shut it down immediately after a hard run, etc. In cases like that, synthetic will delay the inevitable turbo failure a bit.
JHZR2
Staff member
+1
I agree with everyone else here...I haven't heard of this being a big issue. If you are concerned there are a couple of things you can do. First install an exhaust temperature gage to monitor the temps...when higher than 350 degree pre-turbo...let it idle for a minute or so before shutting down. And second you can install a delay system that lets you set the amount of time the truck will idle before shutting down with the key off and in your pocket. I did both of the above...probably overkill...but what the heck it is only money.
Dont forget that most modern turbos are water cooled, allowing the coolant to heat soak after shut down rather than the oil.
I wouldn't say that syn oil will not coke your turbo if the engine is shut off when really hot and what is the coking point of the various syn base stocks? I am sure a watercooled turbo helps .
dnewton3
Staff member
If one were to run a very hard, long pull and then immediately shut down, perhaps the EGTs would have heat-soaked the turbo enough to cause a potential concern; perhaps not.
This can be eliminated by simply letting the vehicle run at idle for a moment or two to let the EGTs drop, and then dino oils won't have any issue whatsoever.
In fact, I'm not convinced that a PAO would survive a grossly heat-soaked turbo at shutdown that much better than a dino; they can only do so much and are NOT miracle fluids. Better? Yes. But NOT perfect.
This can be eliminated by simply letting the vehicle run at idle for a moment or two to let the EGTs drop, and then dino oils won't have any issue whatsoever.
In fact, I'm not convinced that a PAO would survive a grossly heat-soaked turbo at shutdown that much better than a dino; they can only do so much and are NOT miracle fluids. Better? Yes. But NOT perfect.
I've seen coked turbo bearings.
One vehicle/owner in particular. Petrol, aftermaret turbo, 18lb boost. GTX 20W-50, no idle down, and two trashed cartridges.
Agip Sint 2000, and no probs.
Diesel EGTs are lower in normal operation, and didn't show issues through the 80s
One vehicle/owner in particular. Petrol, aftermaret turbo, 18lb boost. GTX 20W-50, no idle down, and two trashed cartridges.
Agip Sint 2000, and no probs.
Diesel EGTs are lower in normal operation, and didn't show issues through the 80s
Originally Posted By: dnewton3
In fact, I'm not convinced that a PAO would survive a grossly heat-soaked turbo at shutdown that much better than a dino; they can only do so much and are NOT miracle fluids. Better? Yes. But NOT perfect.
It might have been more of an issue years ago with inferior oils. Besides, even if we were to assume that PAOs were perfect with respect to heat in such a scenario, we know that oils aren't anywhere near 100% PAO.
Year ago, on farm machinery, I ran full throttle/max boost for hours on end using 15w-40 conventional in turbodiesel tractors. One simply didn't go straight to idle and shut down, that's all.
In fact, I'm not convinced that a PAO would survive a grossly heat-soaked turbo at shutdown that much better than a dino; they can only do so much and are NOT miracle fluids. Better? Yes. But NOT perfect.
It might have been more of an issue years ago with inferior oils. Besides, even if we were to assume that PAOs were perfect with respect to heat in such a scenario, we know that oils aren't anywhere near 100% PAO.
Year ago, on farm machinery, I ran full throttle/max boost for hours on end using 15w-40 conventional in turbodiesel tractors. One simply didn't go straight to idle and shut down, that's all.
Although dino oils will not offer the same protection as synthetic oils, dino oils have come a long way. I am using Delo 15w40 and my 7.3 seems to do ok with it.
Our OTR trucks and heavy equipment ALWAYS gets a cool down period after hard use,gets ya fired if you don't!
Synthetics definitely can still coke in the turbo, but at a given temperature, they'll coke a bit less, delaying the user-induced failure.
I've run my fair share of dino and HDEO oils in my '00 VW GTI 1.8L Turbo. My factory turbo seems fine at 165K miles.
Modern turbos can run at speeds over 100,000 rpm. Why take a chance with a conventional HDEO, when a longer oil change interval with a synthetic oil can eliminate the cost difference?
I have a turbo timer on my Pajero,but hardly ever use it.I very seldom go from full load full boost to stopping and shutting down - there is usually a period of driving around city or town streets before I stop,that's enough cooling down time.335,000km and the turbo is prefect.
wemay
Site Donor 2023
I know this is a 5 year old thread but while reading my Owner's Manual, 15w40 is listed as one option for the 2.0Turbo. Under what conditions would this viscosity be favorable? I do see that many of these oils are dually rated for diesel/PCMO.
- Status
Similar threads
- Sticky
