i want to avoid coking/shearing in a turbo car

[mino]

correct my statement if needed - the turbo bearings get very hot during turbo cooldown - this is when coking happens ( heat breakdown that causes oil to form solids in/around bearings of turbo when otherwise cooling would take place during normal engine operation ) - to avoid this - longer cool down peiods allow turbo to circulate oil and water around itself to bring temp down . if you neglect the cooldown period the oil around the bearing sits on the hot bearing and is subjected to coking - shearing is the wiping of oil off a metal surface on a microscopic level thus causing metal on metal contact and wear - QUESTION - would the best choice of full synthetic oil avail over the counter be either pennzoil platinum ; mobile 1 ;castrol syntex ; royal purple - thanks for input - i know alot recommend amsoil , but i prefer a retail chain store brand

 

[ConfederateTyrant]

You could use any of those and be safe, as long as you didn't use the oil too long. All of the cooldowns can be detrimental to the length of your OCI, as the oil will begin to breakdown without actually being used inside the engine.

If you want to stay conservative, then any of those oils at 5,000 mile intervals should be more than adequate.

 

[BuickGN]

Cool down is part of the reason I use a Preluber. It continues to circulate oil after the motor is shut down. I'm not a big fan of water cooled turbos except in the Porsche 951. They do it the right way with a small electric water pump that continues to run after the engine is shut down. With the motor shut off and oil shut off, heat from the turbine side tries to heat up the center section to the same temp.

I've never had a turbo failure even before the preluber except from extreme abuse. Just make sure you drive it easy at least 2 miles before you shut it off and give it some idle time. For what it's worth, after a hard run, mine will glow for a few minutes no matter if the engine is on or off. I've had great luck with cheap dino oil but I change the oil from 500- 1,000 miles.

 

[TallPaul]

If it were my car, I would be running Redline. Delivered to my door is better than over the counter, though I can get it at Detroit Speed Shops about 6 miles from me. You may have a hot rod shop in your town that sells it. I believe Redline will out perform any of the oils you listed in your application.

 

[gtx510]

If I'm flogging my car I'll run the heater for a few minutes before shutting her down. It helps if your driving around slowly, both for radiator airflow and rpm's to get your coolant flowing.
I stay away from 30wt oils, but I might try GC 0W30 this winter.

Most turbos are water cooled, oil cooled is old technology. I think lotsa European cars come with auxillary (electric) water pumps that help keep flow going to the heater core while they're idling. Some might run after the engine is off, I know some BMW fans will do that.
I've been thinking about adding an auxillary pump to my 323GTX. Does anyone have more info on them?

 

[Saab9-3]

My saab has a water/oil cooled turbo, always let it sit for a min before turning it off and had no issues on my uoa's.

As per oils,, why not give Elf, Motul a shot, as they are both euro's and designed toward the Euro market .

Personally with my Saab, it has never run smoother (currently running Elf). I use to run XD3 in her.

What kind of car are you driving ? Turbo ? Boost ? type of driving ?

 

[Nederlander75]

Originally Posted By: TallPaul
If it were my car, I would be running Redline. Delivered to my door is better than over the counter, though I can get it at Detroit Speed Shops about 6 miles from me. You may have a hot rod shop in your town that sells it. I believe Redline will out perform any of the oils you listed in your application.


It doesnt do bad in my UOA comps, but I have had better Oxid and Nitr numbers from RP than RL and certainly better than M1. That said the best I have found has been NEO.

 

[TallPaul]

Okay, Elf, Motul, Neo, I think are all on the same order as Redline. Go for the best when running turbo.

 

[Eddie]

Mobil 1 & Pennzoil Plat in 5w30 meet the new Honda/Acura turbo spec. I assume other may but, have not been tested. Based on present approval spec I'd use Mobil 1 or PP. Both of these oils are avail at WalMart in 5 quart jugs for 20-23 dollars.

 

[mitchcoyote]

Mobil 1

 

[LargeCarManX2]

Just buy the best synthetic oil that meets the engine builders specs. The engine can be monitored by a few things during cool-down.

1. Oil pressure (you want to bring the rpm's up a tad from idle)

2. Turbo heat (a pyrometer measures the heat of the turbo)

If your oil can take the heat of the bearings after a cooldown period. Where you kept the oil flowing past/through the bearings by a slightly elevated rpm to raise the oil pressure. And allowed the turbo to cool to 800-900 degrees....a quality oil won't coke or shear at the temp after shut-down.

 

[jorton]

mino, heavy duty mixed fleet 10w-30 or 15w-40 like Shell Rotella is a good quality-cost compromise when you have to change oil in a turbo 4 or 5 times a year due to fuel dilution.

 

[gtx510]

Best over the counter turbo oil?
A synthetic HDEO.
Rotella 5W40, M1 TDT (Delvac 1) 5W40, M1 10W40, etc.
Something with a A3/B3 or A3/B4 rating...

 

[BuickGN]

I don't agree with the statement that oil cooled turbos are obsolete. Water cooled is great if you have an aux pump that circulates water after the motor is shut down. If not, they do nothing for you. The water that is left in the turbo will vaporize and leave it as if it were a regular non-water cooled turbo.

With the newer ball bearing turbos, less oil is fed to the bearings vs the older bushing style so maybe water cooling has a place there. Regardless, I haven't had a lubrication failure in the 120,000 miles I've had my turbo car with regular dino oil and non-water cooled turbo. Driving easy for a couple miles before your destination goes a long way for turbo life. Or in my case, letting the car idle while I wait 5 minutes for the windows to roll up.

My EGTs stay around 4-600 degrees during normal driving but hit upwards of 1,650 degrees under WOT and high boost. You can see where driving easy would help a little with turbine heat.

 

[gtx510]

I didn't mean to say that oil cooled turbos are obsolete, just that they are the older technology. Oil cooled Garretts are the like older T04B, the TO4E is water cooled and I think they also have improved wheels. I can't think of a modern car turbo that isn't water cooled. If you're running an oil cooled turbo then the turbo shop cheaped out a little on your upgrade by using an older style center section. You don't see this alot outside of custom T3's or T4's. If it saves you money, it saves you money.
If you allow the turbo to cool down some then an oil cooled turbo isn't bad. But, imho, a water cooled turbo would be better for most people. Water cooled turbos were standard in the middle-late 80's, way before BB turbos were available to the public. That was F1 territory back then.

Just curious. Is you EGT sensor before or after the turbo?

 

[BuickGN]

Originally Posted By: gtx510
I didn't mean to say that oil cooled turbos are obsolete, just that they are the older technology. Oil cooled Garretts are the like older T04B, the TO4E is water cooled and I think they also have improved wheels. I can't think of a modern car turbo that isn't water cooled. If you're running an oil cooled turbo then the turbo shop cheaped out a little on your upgrade by using an older style center section. You don't see this alot outside of custom T3's or T4's. If it saves you money, it saves you money.
If you allow the turbo to cool down some then an oil cooled turbo isn't bad. But, imho, a water cooled turbo would be better for most people. Water cooled turbos were standard in the middle-late 80's, way before BB turbos were available to the public. That was F1 territory back then.

Just curious. Is you EGT sensor before or after the turbo?


It's before the turbo. I originally had it in the downpipe but the exhaust would lose ~200 degrees or more after the turbo depending on how much throttle I gave it.

I agree with your post. Water cooled turbos are definately better for the average person that doesn't know how to care (or doesn't care) for turbos. With a proper setup you don't have to worry about cool down which is nice at times. It doesn't bother me but my car is retired to toy/weekend status. It got annoying in it's daily driver days.

I would love to try some of the new Garrett "GT" series turbos but I'm still running an old PTE-67 from 5 years ago. I even went so far as to build a bigger 4.2L motor (up from a 3.8) not for power but for better spool. If the newer turbo technology was around back then it could've saved me some money.

 

[brianl703]

Originally Posted By: BuickGN
Water cooled is great if you have an aux pump that circulates water after the motor is shut down. If not, they do nothing for you. The water that is left in the turbo will vaporize and leave it as if it were a regular non-water cooled turbo.


First, it ought to be noted that one of the laws of physics says that if the coolant is vaporizing, it is removing heat from the turbo.

Second, let me quote what Saab has to say about the subject:

"The turbocharger is water-cooled, which lowers the temperature in the bearing housing considerably. Temperature reduction reduces the risk of the oil boiling and the damages that can arise from such. Coolant is taken via a pipe from the cylinder head. After passing the bearing housing, coolant is led further via pipes to the thermostat housing. When the engine has been switched off and the coolant pump has stopped, coolant in the system self-circulates through thermosiphoning."

Incidentally, Saab recommends Mobil 1 0W40 or Castrol Syntec 0W30 for the car that this service manual information is quoted from. (The GM LL A 025 spec)

 

[DABEAR95]

IMO a top quality oil and 30-45 seconds of idle time should work will in almost all cases unless you just finished racing...


With that said I use the TIT as a gauge to tell me when to shut down. Once the EGT gauge shows a normal idle temp, I shut her down. My turbo is a variable nozzle oil cooled unit.


Jason

 

[BuickGN]

Originally Posted By: brianl703
Originally Posted By: BuickGN
Water cooled is great if you have an aux pump that circulates water after the motor is shut down. If not, they do nothing for you. The water that is left in the turbo will vaporize and leave it as if it were a regular non-water cooled turbo.


First, it ought to be noted that one of the laws of physics says that if the coolant is vaporizing, it is removing heat from the turbo.

Second, let me quote what Saab has to say about the subject:

"The turbocharger is water-cooled, which lowers the temperature in the bearing housing considerably. Temperature reduction reduces the risk of the oil boiling and the damages that can arise from such. Coolant is taken via a pipe from the cylinder head. After passing the bearing housing, coolant is led further via pipes to the thermostat housing. When the engine has been switched off and the coolant pump has stopped, coolant in the system self-circulates through thermosiphoning."

Incidentally, Saab recommends Mobil 1 0W40 or Castrol Syntec 0W30 for the car that this service manual information is quoted from. (The GM LL A 025 spec)


The theory is great and I do understand what you're saying. But in the real world, our members that had coking problems with traditional turbos had the same problems with water cooled. There are a few ounces of water left in the bearing housing at the most. The 10lbs of 600 degree cast iron in the turbine housing is going to boil it quickly. Thermosiphoning may occur in some setups depending on how the turbo is mounted and how the coolant hoses are routed. For the cars I deal with, the turbo is higher than the coolant level so it's doubtful the coolant will flow uphill with the engine off.

I still stand by my theory that proper cool down is more effective than a water cooled center section but not to say that the water cooling doesn't help a little.

 

[brianl703]

Originally Posted By: BuickGN
Thermosiphoning may occur in some setups depending on how the turbo is mounted and how the coolant hoses are routed. For the cars I deal with, the turbo is higher than the coolant level so it's doubtful the coolant will flow uphill with the engine off.


I'm sure the cooling system can be engineered to ensure that thermosiphon will take place. For example:

In the case of the Saab the pressurized coolant tank is the highest part of the cooling system. I'm sure this is to allow thermosiphon to take place(as well as to eliminate air pockets after a drain/refill). The Saab is also configured to allow the electric radiator cooling fans to come on after the engine has been shut off, based on readings from the engine coolant temp. sensor, and in fact I have seen this happen several times. This probably also plays a role in allowing thermosiphon to take place.