Oil weight vs protection question

[aquariuscsm]

I`d read on another car forum where a guy tracking his car with M1 15W50 spun a bearing. It seems people have had that happen with both thick and thin oils when racing,tracking,etc. So would spun bearings/engine failure be the result of oil starvation only,regardless of oil weight? Say for instance,a car specs 10W30-20W50. Would a 0W20 protect the engine as well as a 40 or 50 weight if said car was racing/tracking for extended runs as long as the oil supply wasn`t interrupted? I know a guy who uses M1 0W20 in his Z32 twin turbo (fsm says not to use 5W30 or lower) who regularly tracks,and never has any issues at all.

 

[simple_gifts]

I think oil temperature would be the deciding factor; Weight is @ X degrees. If it is 2X or 3X oil temp "It is going to be a factor"

 

[chubbs1]

There are several different states of lubrication. Some racers use really light weight oils (0w10/0w5)! While others use thicker oil, I think (this is the easy way out) the jury is still out on what is the "best". If you are going to have a problem it is going to be at the weakest link and I don't know if any oil can prevent it.

 

[electrolover]

there are alot of different things that can spin a bearing. poor machine work improper oil selection or just plain poor design.
the clearances and oil temp are whats going to determine your oil choice, so its a good idea to talk to your engine builder about oil selection. tell him what your going to be doing with the engine and what you need AND LISTEN to what he has to say.


on the drag strip i have had good luck with plain ole 10/30 in a stock engine but i have also had great luck with 20/50 in clearanced engines

 

[SrDriver]

We live near the Florida line and run 5W20 synthetic year around. Long hot summers. Have used in the last 4 vehicles with no problems.

Police use 5W20 too and vehicles see hard abuse with long periods of idling.

 

[CATERHAM]

The oil grade is not important, oil pressure is.
Run the lightest oil that provides the minimum optimum OP when the oil is as hot as it normally gets.
It's that simple.

 

[Torino]

Plain bearings derive their protection by the formation of a 'hydro thermic' wedge. The effectiveness of this wedge is mainly dependent upon the adhesion of the oil to the bearing surfaces in question. Point-most HIGH powered dragsters use 50-70 wt. ester oil. Its quite 'sticky' so to say. Whats the best for any given application? I don't know. Use what ever works for you. John--Las Vegas.

 

[Bullet]

Many spun bearings are a result of over revving the engine and the rod bolts stretch. And over heating the oil will do it too.

 

[A_Harman]

Originally Posted By: aquariuscsm
So would spun bearings/engine failure be the result of oil starvation only,regardless of oil weight?


Assuming the engine was built right in the first place, yes. As long as the bearings have a steady supply of oil, they will live. I qualify that by saying an oil should be used that has higher than the minimum HTHS viscosity recommended by the manufacturer. If starvation occurs, a higher viscosity oil will buy perhaps a few more tenths of a second before the oil film burns away, and the bearings weld to the crank.

Originally Posted By: aquariuscsm
Would a 0W20 protect the engine as well as a 40 or 50 weight if said car was racing/tracking for extended runs as long as the oil supply wasn`t interrupted? I know a guy who uses M1 0W20 in his Z32 twin turbo (fsm says not to use 5W30 or lower) who regularly tracks,and never has any issues at all.


The simple answer to this question is no, if one only considers that higher viscosity means higher film thickness. But there is more to it than that. An oil system not only consists of the passages pressurized by the oil pump, but also the passages that return oil to the sump after it has been ejected from the bearings. It is axiomatic that oil must return to the sump at the same rate it is pumped from the sump if steady oil supply is to be assured. This is where a thinner oil helps, because the lower kinematic viscosity speeds the return of the oil to the sump, making it less likely that oil starvation occurs in the first place. But you can go too far with thin oil, if it doesn't have high enough HTHS viscosity to maintain adequate film thickness in the bearings, bearing wear will also occur.

Call this the Goldilocks theory of oil viscosity selection: not too thick, not too thin, but just right.

 

[CATERHAM]

The minimum HTHS viscosity set by virtually all engine manufacturers is 3.5cP. This translates into a minimum heavy 30wt oil. So how can anyone run a 20wt with a HTHS vis of only 2.6cP (or less after shearing) on tne street let alone on the track?
Simple; low oil temperatures. The engine has no idea what the HTHS vis' rating is of any oil, all it knows is what the operational viscosity is at any given moment.
Oil presure is the best proxy for that operational viscosity.
If you maintain the minimum oil pressure (back pressure actually)
that's specified by the mfter you are by def'n maintaining a safe minimum viscosity for your engine with virtually no chance of bearing wiping.

That's why race cars can run 5wt qualifying oil or even 2wt drag oil with HTHS vis' as low as 1.4cP because the oil in the bearings of the engine doesn't have time to get too hot.

I

 

[A_Harman]

I take the viscosity recommendations that the manufacturers put in their service manuals as signifying the minimum HTHS that is safe to run in their engines. An engine that is specified for an Xw20, should be safe to run 2.6cP oil. An engine that is specified for Xw30, should be safe on 2.9cP oil. Heavy duty engine manufacturers generally specify 3.5cP as minimum HTHS. This is met by 40-weight oils, which are divided into two groups; 0, 5, & 10W-40 and 15, 20, and 25W-40. It used to be that 0, 5, & 10W's could have 2.9cP min HTHS, and 15, 20, and 25W's would have 3.7 min. This is why 15W40 was the predominant weight of HDEO's, although there were certainly many "lower 40" oils that exceeded 3.5 HTHS.

 

[440Magnum]

My hunch would be that most "spun bearing" failures aren't really oil-related at the root of the matter. My guess is that most are due to over-revving or under-spec rod bolts, stretching the rod bolts, losing the clamping force on the bearing shell, and allowing the initial rotation. After that initial rotation, the oil hole is blocked and the locating tangs are grinding against the journal, so failure happens REALLY fast after that.

Yes, you can fail a bearing through oil starvation, but the honest truth is the *mains* will starve before the rods in many cases because the crank acts as a centrifuge, raising effective oil pressure at the rod bearings at the cost of lowering it at the mains. If the flow rate can't keep up, it'll be a main that goes dry *first* followed by a rod.

 

[CATERHAM]

Originally Posted By: A_Harman
I take the viscosity recommendations that the manufacturers put in their service manuals as signifying the minimum HTHS that is safe to run in their engines. An engine that is specified for an Xw20, should be safe to run 2.6cP oil. An engine that is specified for Xw30, should be safe on 2.9cP oil. Heavy duty engine manufacturers generally specify 3.5cP as minimum HTHS. This is met by 40-weight oils, which are divided into two groups; 0, 5, & 10W-40 and 15, 20, and 25W-40. It used to be that 0, 5, & 10W's could have 2.9cP min HTHS, and 15, 20, and 25W's would have 3.7 min. This is why 15W40 was the predominant weight of HDEO's, although there were certainly many "lower 40" oils that exceeded 3.5 HTHS.

Today most German engine mfters stipulate an oil with a minimum 3.5cP HTHS rating. Does that mean you can't safely run a lighter oil? Of course you can. It is only with the advent of 0W-30 and 0W-40 oil grades that they did away with recommending 20wt and light 30wt oils for warranty purposes. For example my older Porsche manual recommends 5W-20 at ambient temp's below 0C and no high speed driving. Anyone using a 20wt oil of the day who forgot to change out the oil for the appropriate oil grade based on summer ambient temp's would no doubt experience accelerated engine wear when crusing at 150 mph on the autobahn if the oil temp's soared into the 130C range.
Today mfters can avoid the whole problem by simply specifying a 0W-XX oil of a known quality with a minimum operational viscosity (HTHS vis') and still have (not ideal but) acceptable extreme cold start performance.

Mfters who spec' 20 wt oil have their oil temp's well under control even under extreme operating conditions. I would argue that no engine spec'd for a 2.6cP HTHS 20wt would still be able to operate under maximum load with oil temp's in the 140C range without experiencing bearing wiping particularly with an oil that has sheared down into the 2.2cP area or in an engine that experienced unexpected fuel dilution (such as a leaking fuel injector).
IIRC truck mfters such as Toyota and Ford that recommend 20wt oil do also suggest 5W-30 for extreme duty applications to cover their buts.

When I say oil pressure is the bottom line, what I'm really saying is a certain minimum optimum operational viscosity is what one ideally want's to know, not the oil grade, and the only way to know how close to that optimum operational viscosity you're running is with an oil pressure gauge.

 

[440Magnum]

Originally Posted By: CATERHAM

IIRC truck mfters such as Toyota and Ford that recommend 20wt oil do also suggest 5W-30 for extreme duty applications to cover their buts.


Funny you mention this, because I just stumbled across the appropriate entry in the 08 Ram manual last week. Chrysler recommends 5w20 for all 3.7 & 4.7 Ram 1500 engine applications, as well as for all 5.7 applications less than 14,000 lb gross vehicle weight (with the footnote that Xw20 is critical for 5.7L engines with MDS/VVT). For any gasoline engine application over 14,000lb GVW- which basically means a Ram 2500 or 3500 with a trailer- then 5w30 is recommended. Technically no 4.7 should ever wind up at over 14,000 lb, so I'm sure that's the only reason it isn't called out as well. Were I thinking about pushing a 4.7 right to the limit, I'd go with a 5w30, 5w40, or 0w40 personally.

 

[Jeff_in_VABch]

Originally Posted By: aquariuscsm
I`d read on another car forum where a guy tracking his car with M1 15W50 spun a bearing.


What is tracking?

If this is drag racing, the 15W50 would be too high a viscosity. At a drag strip, you sit in the staging area for quite a while and the engine is cool to cold at the start tree. Plain engine bearings will spin when cold and subjected to high oil pressure and load. I see this happen on the engine dyno when testing is started before a full warm-up (160-170F oil).

If it is closed circuit racing, M1 15W50 is very good.

Originally Posted By: aquariuscsm
So would spun bearings/engine failure be the result of oil starvation only,regardless of oil weight?


On a hot engine, worn bearings or a high RPM excursion (missed shift)are the usual culprits.

 

[NYH]

Originally Posted By: 440Magnum
Originally Posted By: CATERHAM

IIRC truck mfters such as Toyota and Ford that recommend 20wt oil do also suggest 5W-30 for extreme duty applications to cover their buts.


Funny you mention this, because I just stumbled across the appropriate entry in the 08 Ram manual last week. Chrysler recommends 5w20 for all 3.7 & 4.7 Ram 1500 engine applications, as well as for all 5.7 applications less than 14,000 lb gross vehicle weight (with the footnote that Xw20 is critical for 5.7L engines with MDS/VVT). For any gasoline engine application over 14,000lb GVW- which basically means a Ram 2500 or 3500 with a trailer- then 5w30 is recommended. Technically no 4.7 should ever wind up at over 14,000 lb, so I'm sure that's the only reason it isn't called out as well. Were I thinking about pushing a 4.7 right to the limit, I'd go with a 5w30, 5w40, or 0w40 personally.

Chrysler recommends 5W-20 oil for two main reasons 1- to meet the CAFE standards like everyone else, 2- the MDS system in their Hemi vehicles that drops 4 of the cylinders to improve fuel mileage works with less resistance on the engine like flat cruising speeds without the vehicle having a heavy load or towing. The lifters are what controls the MDS system. They need thinner oil to do so. 5W-30 oil almost never lets the MDS system kick in. Their cars had the MDS system first then their SUV's and 1/2 trucks started using the MDS system in '06. My '05 Hemi Durango called for 5W-30. My '07 Hemi Ram calls for 5W-20. The 3/4 and 1 ton Hemi's trucks didn't have the MDS system so thicker oil can be used. My fathers '06 4.7L Dakota calls for 5W-30. Now I'm pretty sure all their gasoline powered vehicles call for 5W-20 oil to meet CAFE standards.

 

[demarpaint]

Originally Posted By: NYH
Originally Posted By: 440Magnum
Originally Posted By: CATERHAM

IIRC truck mfters such as Toyota and Ford that recommend 20wt oil do also suggest 5W-30 for extreme duty applications to cover their buts.


Funny you mention this, because I just stumbled across the appropriate entry in the 08 Ram manual last week. Chrysler recommends 5w20 for all 3.7 & 4.7 Ram 1500 engine applications, as well as for all 5.7 applications less than 14,000 lb gross vehicle weight (with the footnote that Xw20 is critical for 5.7L engines with MDS/VVT). For any gasoline engine application over 14,000lb GVW- which basically means a Ram 2500 or 3500 with a trailer- then 5w30 is recommended. Technically no 4.7 should ever wind up at over 14,000 lb, so I'm sure that's the only reason it isn't called out as well. Were I thinking about pushing a 4.7 right to the limit, I'd go with a 5w30, 5w40, or 0w40 personally.

Chrysler recommends 5W-20 oil for two main reasons 1- to meet the CAFE standards like everyone else, 2- the MDS system in their Hemi vehicles that drops 4 of the cylinders to improve fuel mileage works with less resistance on the engine like flat cruising speeds without the vehicle having a heavy load or towing. The lifters are what controls the MDS system. They need thinner oil to do so. 5W-30 oil almost never lets the MDS system kick in. Their cars had the MDS system first then their SUV's and 1/2 trucks started using the MDS system in '06. My '05 Hemi Durango called for 5W-30. My '07 Hemi Ram calls for 5W-20. The 3/4 and 1 ton Hemi's trucks didn't have the MDS system so thicker oil can be used. My fathers '06 4.7L Dakota calls for 5W-30. Now I'm pretty sure all their gasoline powered vehicles call for 5W-20 oil to meet CAFE standards.



Isn't the Pentastar engine using an MDS system? It calls for 5W30 oil IIRC. CAFE is only a part of it. Ford is using 5W30 in the eco-boost engines too I think.

 

[A_Harman]

The Pentastar doesn't have MDS.

 

[A_Harman]

Originally Posted By: Jeff_in_VABch
Originally Posted By: aquariuscsm
I`d read on another car forum where a guy tracking his car with M1 15W50 spun a bearing.


What is tracking?

If this is drag racing, the 15W50 would be too high a viscosity. At a drag strip, you sit in the staging area for quite a while and the engine is cool to cold at the start tree. Plain engine bearings will spin when cold and subjected to high oil pressure and load. I see this happen on the engine dyno when testing is started before a full warm-up (160-170F oil).

If it is closed circuit racing, M1 15W50 is very good.

Originally Posted By: aquariuscsm
So would spun bearings/engine failure be the result of oil starvation only,regardless of oil weight?


On a hot engine, worn bearings or a high RPM excursion (missed shift)are the usual culprits.


Tracking = track days = Non-competitive driving on closed-circuit road courses. Participants can expect to get 1.5 -3 hours of track time in a day, depending on the organization. This gives enthusiasts a chance to thoroughly enjoy their cars without John Law spoiling the fun.

 

[demarpaint]

Originally Posted By: A_Harman
The Pentastar doesn't have MDS.


Good to know, one less thing that can go wrong with it. LOL