Turbos in themselves don't shear oil - the oil is in the bearings - not the spinning blades. It is the intense isolated heat that 'burns up' the oil and cooks it into submission.
Do turbos damage oil?
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Originally Posted By: Shannow
Back in the day, a neighbour had an early (80s) aftermarket turbo on a 240 Volvo...18psi boost, with all of the gapless, forged, tricky bits...pre water cooled bearings.
Bloke who installed the aftermarket stuff argued that regular GTX was all that was needed, and that idle down was a fad.
Neighbour chewed up a number of centre sections (actually, whole turbos at that stage of the market in Oz, and finally decided on Agip sint 2000 10W-50, idle down to the point that he and his family had their seatbelts off, lights off etc....then used the 5,000km old oil a second time in his Datsun 1000/1200s beaters...way cheaper than new turbos.
A few points:
* aftermarket, non water cooled;
* aftermarket, high boost;
* mineral oil, no idle down.
That were solved by synthetic oil and idle down.
A petrol engine runs at stoichiometric, or pretty close, so has a pretty constant exhaust temperature, and during the idle down period, the exhaust system can get rid of the heat that has accumulated during use.
When you shut off the engine, the oil flow through turbo bearings stops, and what oil that remains has to cope with the heat that's left...hotter metal, hotter oil, more coke. (Water cooled helps a lot with this)...pulling off a highway into a petrol station is bad news on a petrol turbo.
Wouldn't worry about genuine shearing too much, as the bearings are hydrodynamic, and the radial loads on a turbo are comparatively light.
Diesel turbos are a different kettle of fish, as running lean of stoichiometric, the exhaust gasses are cooler...pulling off the highway into a petrol station not nearly so bad, certainly not ideal, but not as bad as petrol turbo.
Maybe that's why HDMOs are "apparently" so shear stable...they can be wrecked in a motorcycle transmission in short order, for all of their "stability".
Good post, if you don't have a newish car with an electric run on turbo oil pump that takes care of the few minutes required to cool the bearings it is bad news for both the bearings and oil.
Sudden stops for a call of nature on the German autobahn are bad news for old turbos, as it's possible to go from full power to shut down in 30 seconds as the entrance road are short. It takes longer to pull into the fuel stations, so I think it's the sudden calls of nature doing the damage. Stepping on the gas when cold is nearly as bad.
Turbo boost settings and temperatures vary a lot between different cars and the manufacturers approved oil guide will give good info on the type of oil required. My old Volvo TDI does not need even an HC synthetic, but the new TDI has a very serious full synthetic requirement listed due to a different turbo and engine.
Back in the day, a neighbour had an early (80s) aftermarket turbo on a 240 Volvo...18psi boost, with all of the gapless, forged, tricky bits...pre water cooled bearings.
Bloke who installed the aftermarket stuff argued that regular GTX was all that was needed, and that idle down was a fad.
Neighbour chewed up a number of centre sections (actually, whole turbos at that stage of the market in Oz, and finally decided on Agip sint 2000 10W-50, idle down to the point that he and his family had their seatbelts off, lights off etc....then used the 5,000km old oil a second time in his Datsun 1000/1200s beaters...way cheaper than new turbos.
A few points:
* aftermarket, non water cooled;
* aftermarket, high boost;
* mineral oil, no idle down.
That were solved by synthetic oil and idle down.
A petrol engine runs at stoichiometric, or pretty close, so has a pretty constant exhaust temperature, and during the idle down period, the exhaust system can get rid of the heat that has accumulated during use.
When you shut off the engine, the oil flow through turbo bearings stops, and what oil that remains has to cope with the heat that's left...hotter metal, hotter oil, more coke. (Water cooled helps a lot with this)...pulling off a highway into a petrol station is bad news on a petrol turbo.
Wouldn't worry about genuine shearing too much, as the bearings are hydrodynamic, and the radial loads on a turbo are comparatively light.
Diesel turbos are a different kettle of fish, as running lean of stoichiometric, the exhaust gasses are cooler...pulling off the highway into a petrol station not nearly so bad, certainly not ideal, but not as bad as petrol turbo.
Maybe that's why HDMOs are "apparently" so shear stable...they can be wrecked in a motorcycle transmission in short order, for all of their "stability".
Good post, if you don't have a newish car with an electric run on turbo oil pump that takes care of the few minutes required to cool the bearings it is bad news for both the bearings and oil.
Sudden stops for a call of nature on the German autobahn are bad news for old turbos, as it's possible to go from full power to shut down in 30 seconds as the entrance road are short. It takes longer to pull into the fuel stations, so I think it's the sudden calls of nature doing the damage. Stepping on the gas when cold is nearly as bad.
Turbo boost settings and temperatures vary a lot between different cars and the manufacturers approved oil guide will give good info on the type of oil required. My old Volvo TDI does not need even an HC synthetic, but the new TDI has a very serious full synthetic requirement listed due to a different turbo and engine.
Originally Posted By: GearheadTool
Originally Posted By: Shannow
...pulling off a highway into a petrol station is bad news on a petrol turbo
I knew there was a reason to leave it running during fill-ups! It cools the turbo!
Most likely all you are doing is wasting petrol.
Any modern car is fitted with a few things from an engineering perspective to promote good bearing health:
1. water and oil cooled bearings by design
2. Gravity fed coolant system so when turning car off, coolant can continue to flow a tad through the turbo bearings if needed
Its still advisable to run a good full synthetic with a turbo but the reasons are more for overall engine health as more and more cars go to longer OCIs.
Back in the day with standard sleeve bearing turbos, no water cooling, high boost operation, a hot run off the highway followed by a quick shut down meant that sleeve bearing and its thin film of oil was left to cool on its own after running near 100K RPM.
Harsh stuff for a motor oil, so you wanted something solid to help with this bad behavior.
Folks who install turbo timers and other items in modern street cars are just trying to relive the fast and the furious: they are not needed.
- bvl
2002 stage 2 WRX 132K and going
1992 MX5 FM 2 aftermarket G25/28 turbo 150K an no rebuild
Mostly M1, now on PU
Originally Posted By: Shannow
...pulling off a highway into a petrol station is bad news on a petrol turbo
I knew there was a reason to leave it running during fill-ups! It cools the turbo!
Most likely all you are doing is wasting petrol.
Any modern car is fitted with a few things from an engineering perspective to promote good bearing health:
1. water and oil cooled bearings by design
2. Gravity fed coolant system so when turning car off, coolant can continue to flow a tad through the turbo bearings if needed
Its still advisable to run a good full synthetic with a turbo but the reasons are more for overall engine health as more and more cars go to longer OCIs.
Back in the day with standard sleeve bearing turbos, no water cooling, high boost operation, a hot run off the highway followed by a quick shut down meant that sleeve bearing and its thin film of oil was left to cool on its own after running near 100K RPM.
Harsh stuff for a motor oil, so you wanted something solid to help with this bad behavior.
Folks who install turbo timers and other items in modern street cars are just trying to relive the fast and the furious: they are not needed.
- bvl
2002 stage 2 WRX 132K and going
1992 MX5 FM 2 aftermarket G25/28 turbo 150K an no rebuild
Mostly M1, now on PU
Originally Posted By: mechtech2
Turbos in themselves don't shear oil - the oil is in the bearings - not the spinning blades. It is the intense isolated heat that 'burns up' the oil and cooks it into submission.
The oil seperates the turbo shaft from the bushing in a hydrodynamic wedge of oil; turbo shafts can spin in excess of 100,000 rpm(even higher in some smaller diameter turbos). This action is what causes the shearing as the shaft literally tries to "rip"(technical term) the oil molecules apart between it and the stationary bushing.
Supercity. Not saying that pcmo's are not shear stable, they're just not as shear stable as hdeo's. Quite a few Mfr.'s who have turbo gasoline vehicles also have their own oil specs beyond what api or ilsac require; Porsche a40, Honda hto-06, vw 50X.XX, etc.
Turbos in themselves don't shear oil - the oil is in the bearings - not the spinning blades. It is the intense isolated heat that 'burns up' the oil and cooks it into submission.
The oil seperates the turbo shaft from the bushing in a hydrodynamic wedge of oil; turbo shafts can spin in excess of 100,000 rpm(even higher in some smaller diameter turbos). This action is what causes the shearing as the shaft literally tries to "rip"(technical term) the oil molecules apart between it and the stationary bushing.
Supercity. Not saying that pcmo's are not shear stable, they're just not as shear stable as hdeo's. Quite a few Mfr.'s who have turbo gasoline vehicles also have their own oil specs beyond what api or ilsac require; Porsche a40, Honda hto-06, vw 50X.XX, etc.
Originally Posted By: rrrrrroger
I've got a Beetle with a turbo. Is that thing doing nasty destruction to my oil? Maybe I should cut intervals in half (to 5000).
I wouldn't being doing 10K mile OCI's, that's for sure!
Should this post be in the diesel section? Or are you really getting 55-60 mpg in a gasoline car?
Originally Posted By: rrrrrroger
My replacement car gets 55-60 so I'm saving about 7000 dollars over the next decade. And I like the replacement car much, much better.
( edited for content- full post here: https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Main=86278&Number=2858012 )
I've got a Beetle with a turbo. Is that thing doing nasty destruction to my oil? Maybe I should cut intervals in half (to 5000).
I wouldn't being doing 10K mile OCI's, that's for sure!
Should this post be in the diesel section? Or are you really getting 55-60 mpg in a gasoline car?
Originally Posted By: rrrrrroger
My replacement car gets 55-60 so I'm saving about 7000 dollars over the next decade. And I like the replacement car much, much better.
( edited for content- full post here: https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Main=86278&Number=2858012 )
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Originally Posted By: LineArrayNut
Originally Posted By: rrrrrroger
I've got a Beetle with a turbo. Is that thing doing nasty destruction to my oil? Maybe I should cut intervals in half (to 5000).
I wouldn't being doing 10K mile OCI's, that's for sure!
This is sounding more and more like a TDI.
When using a good 5w40 CJ-4 oil and quality filter, a properly running TDI has no problem doing a 10k OCI. They can be extended quite a ways out from there comfortably.
Originally Posted By: rrrrrroger
I've got a Beetle with a turbo. Is that thing doing nasty destruction to my oil? Maybe I should cut intervals in half (to 5000).
I wouldn't being doing 10K mile OCI's, that's for sure!
This is sounding more and more like a TDI.
When using a good 5w40 CJ-4 oil and quality filter, a properly running TDI has no problem doing a 10k OCI. They can be extended quite a ways out from there comfortably.
With either gas or diesel you should be able to go 10,000 miles if you use a proper full synthetic oil. I do a lot of short trips with my TDI so I only go 5 or 6,000. Others say I am wasting money.
Do NOT use a dyno oil with any turbo. You need the higher flash point to deal with the high heat in a turbo which will cook and coke the oil and ruin your turbo. Also, cool down is often necessary after a long hot run, especially if you just went up a hill before stopping. A turbo can easily run 900 degrees going uphill. Even a synthetic can coke at over about 430 degrees. Once you are idling the exhaust gas temperature goes down fairly quickly, less than five minutes. Coasting to a stop in gear cools the exhaust gas even quicker.
Do NOT use a dyno oil with any turbo. You need the higher flash point to deal with the high heat in a turbo which will cook and coke the oil and ruin your turbo. Also, cool down is often necessary after a long hot run, especially if you just went up a hill before stopping. A turbo can easily run 900 degrees going uphill. Even a synthetic can coke at over about 430 degrees. Once you are idling the exhaust gas temperature goes down fairly quickly, less than five minutes. Coasting to a stop in gear cools the exhaust gas even quicker.
Stick with VW spec oil and your car will thank you. These are picky engines. This is coming from someone whose company car is a VW passat 2.0L TDI with nearly 200k miles and car still runs like new and only seen the regular vw spec oil.
As for the cool down of the turbo after long operation, I wouldn't worry about it too much.
Our passat's turbo is under shrouds, which acts as thermal blankets that allow an even dissipation of heat as the engine cools down.
As for the cool down of the turbo after long operation, I wouldn't worry about it too much.
Our passat's turbo is under shrouds, which acts as thermal blankets that allow an even dissipation of heat as the engine cools down.
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I think it's the oil that has made the biggest difference to the reliability of turbos these days. I'd happily use dino oil in a turbo for some applications and I did for many years. In the USA where Synth is so cheap I would not even bother with dino but here where it can cost $100 a jug for M1 you think twice.
Here's a little story,
For what it's worth I used an ELF/Total dino fleet oil, 15w40 SL era (rated for petrol and diesel turbos) in all sorts of petrol turbo applications, mostly Japanese and Euro. I personally saw many different cars over many years (this is a commercial workshop) and they seemed to run just fine on dino oil. I did notice that the Japanese cars would list 10w30 or 5w30 etc on the oil caps. I just ignored that, they were all too expensive and 15w40 was the right grade for our climate according to the oil charts of the day anyway. It was no uncommon for major dealer to use a 15w40 too.
My mates 94 Subaru WRX saw many track days and regular driving too. It clocked up 180km before he sold it and it never missed a beat. At the time the Subaru dealer was also using a 15w40, "GTX Protec". I did the RC gaskets and there was no varnish. We were not stupid though, they were left to cool down after track driving and we used a conservative OCI.
My own track car had a 1986 Fiat 2L 8V turbo engine. The turbo was a non water cooled Garrett T3. The engine had done 240,000km before I fitted it to my track car. I fitted new bearings and put a gasket set through it before I fitted to the car. It ran about 1 bar of boost, and it got a track day every month. I had no oil temp or pressure gauge. I did strip the turbo after about 2 years to build a T3/T04 hybrid which let me pull another 2000rpm, took the useable powerband from 5500rpm to about 7500rpm. Cooling was then a problem, I use to pull the revs back to 6000rpm once I saw 110C coolant and it would cool down. I'd have vapour spewing out the oil catch tank when pulling into the pits! Thinking the oil may be thinning out a bit too much (it was smoking) I decided to switch to a 15w50 synthetic blend. It was nothing expensive. Sounds barbaric now but it was only a cheap track hack and it was affordable to lose. I sold that car in 2008, it was still going strong, the engine was essentially 23 years old.
Here's a little story,
For what it's worth I used an ELF/Total dino fleet oil, 15w40 SL era (rated for petrol and diesel turbos) in all sorts of petrol turbo applications, mostly Japanese and Euro. I personally saw many different cars over many years (this is a commercial workshop) and they seemed to run just fine on dino oil. I did notice that the Japanese cars would list 10w30 or 5w30 etc on the oil caps. I just ignored that, they were all too expensive and 15w40 was the right grade for our climate according to the oil charts of the day anyway. It was no uncommon for major dealer to use a 15w40 too.
My mates 94 Subaru WRX saw many track days and regular driving too. It clocked up 180km before he sold it and it never missed a beat. At the time the Subaru dealer was also using a 15w40, "GTX Protec". I did the RC gaskets and there was no varnish. We were not stupid though, they were left to cool down after track driving and we used a conservative OCI.
My own track car had a 1986 Fiat 2L 8V turbo engine. The turbo was a non water cooled Garrett T3. The engine had done 240,000km before I fitted it to my track car. I fitted new bearings and put a gasket set through it before I fitted to the car. It ran about 1 bar of boost, and it got a track day every month. I had no oil temp or pressure gauge. I did strip the turbo after about 2 years to build a T3/T04 hybrid which let me pull another 2000rpm, took the useable powerband from 5500rpm to about 7500rpm. Cooling was then a problem, I use to pull the revs back to 6000rpm once I saw 110C coolant and it would cool down. I'd have vapour spewing out the oil catch tank when pulling into the pits! Thinking the oil may be thinning out a bit too much (it was smoking) I decided to switch to a 15w50 synthetic blend. It was nothing expensive. Sounds barbaric now but it was only a cheap track hack and it was affordable to lose. I sold that car in 2008, it was still going strong, the engine was essentially 23 years old.
Originally Posted By: GearheadTool
Originally Posted By: Shannow
...pulling off a highway into a petrol station is bad news on a petrol turbo
I knew there was a reason to leave it running during fill-ups! It cools the turbo!
Dumb dumb very dumb idea. I dont know how many times ive pulled up to a station and drove off because I've seen someone smoking while filling up. A car running while filling up is almost as bad.
Originally Posted By: Shannow
...pulling off a highway into a petrol station is bad news on a petrol turbo
I knew there was a reason to leave it running during fill-ups! It cools the turbo!
Dumb dumb very dumb idea. I dont know how many times ive pulled up to a station and drove off because I've seen someone smoking while filling up. A car running while filling up is almost as bad.
While I don't encourage it, what is the big fear of filling the vehicle's gasoline tank with the engine running?
Unlike a cigarette, a car engine emits no open flame to encounter the gasoline vapors. And if you're concerned about a hot exhaust pipe or catalytic converter, it is just as hot after the engine is shut off.
I'd be more concerned about a zap of static electricity near the filler.
Unlike a cigarette, a car engine emits no open flame to encounter the gasoline vapors. And if you're concerned about a hot exhaust pipe or catalytic converter, it is just as hot after the engine is shut off.
I'd be more concerned about a zap of static electricity near the filler.
Plug wires leak, and for the truly old school, points and distributors constantly spark. The fire is lit in my 1917 Fairbanks-Morse by the spark generated when a set of points opens in the combustion chamber.
I'd agree that static is more likely a problem on a modern, COP equipped vehicle.
Ed
I'd agree that static is more likely a problem on a modern, COP equipped vehicle.
Ed
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