Higher viscosity = higher operating temps?

[ZeeOSix]

Originally Posted by CR94
Interesting chart, RDY4WAR. Assuming the intermediate temperature range, it would've had put 0W-20 or 0W-10 in my 1981 Mazda, for which the service manual specified 0.0009" to 0.0017 clearance for mains.


What did Mazda specify for that engine?

 

[Mad_Hatter]

Originally Posted by CR94
Interesting chart, RDY4WAR. Assuming the intermediate temperature range, it would've had put 0W-20 or 0W-10 in my 1981 Mazda, for which the service manual specified 0.0009" to 0.0017 clearance for mains.

I think those are the optimal viscosities for those clearances. That doesn't mean other viscosities wouldn't be suitable, they just might not be "optimal".

The optimal viscosity is one that provides a) a MOFT that prevents catastrophic wear and b) one not so thick that it creates excessive heat via viscous drag (the lube itself is so thick that it creates friction/heat) and flow reduction. The heat wears on bearings and robs the engine of power and in turn fuel economy.

Many lubes (like an Xw30) could satisfy this requirement so long as the HTHS isn't too high. This is where base oil viscosity and VM type and quantity come in. Too high a 150c HTHS can actually increase wear rates in tight clearances. A case where more is not necessarily a good thing.

 

[CR94]

Originally Posted by ZeeOSix
Originally Posted by CR94
... Assuming the intermediate temperature range, it would've had put 0W-20 or 0W-10 in my 1981 Mazda, for which the service manual specified 0.0009" to 0.0017 clearance for mains.

What did Mazda specify for that engine?
API SE. The manual shows an old-fashioned chart with many viscosity grade options.
5W-20 between -35 and -20°C
5W-30 between -35 and 0°C
10W-30 between -25 and 30°C
10W-40 between -25 and 55°C
10W-50 between -25 and 55°C
20W-20 between -10 and 20°C
20W-40 between -10 and 55°C
20W-50 between -10 and 55°C
SAE 30 between 0 and 40°C
SAE 40 between 30 and 55°C

I'm not claiming that's all logical. Obviously they didn't have much confidence in shear stability of 5W-x0s of 1980. I mostly used 10W-40, with occasional bouts of 10W-30 in cool weather. Never any issues with wear of oily metal parts in 606k miles.

 

[OilUzer]

In the old days they were wiser and used thicker oil. don't worry, the internet people will learn from history and will join the thickies club!

Originally Posted by CR94
API SE. The manual shows an old-fashioned chart with many viscosity grade options.
5W-20 between -35 and -20°C
5W-30 between -35 and 0°C
10W-30 between -25 and 30°C
10W-40 between -25 and 55°C
10W-50 between -25 and 55°C
20W-20 between -10 and 20°C
20W-40 between -10 and 55°C
20W-50 between -10 and 55°C
SAE 30 between 0 and 40°C
SAE 40 between 30 and 55°C

I'm not claiming that's all logical. Obviously they didn't have much confidence in shear stability of 5W-x0s of 1980. I mostly used 10W-40, with occasional bouts of 10W-30 in cool weather. Never any issues with wear of oily metal parts in 606k miles.

 

[ka9mnx]

Originally Posted by CR94
Interesting chart, RDY4WAR. Assuming the intermediate temperature range, it would've had put 0W-20 or 0W-10 in my 1981 Mazda, for which the service manual specified 0.0009" to 0.0017 clearance for mains.

Yes, interesting chart. That would work for your Mazda bearings but remember 40% of engine friction is in the liner, piston and ring area. It is also the most prone area of oil breakdown (viscosity loss). So it would probably be a bad idea for the ring/liner area.

 

[Cujet]

That chart makes little sense with regard to rod bearings. The clearances quoted have little resemblance to any previous or common era conventional engines. The rule is about or around 0.0007 inches of rod bearing clearance, per inch of journal diameter. With wiggle room of 0.0005 inches for rigidity reasons. It's been that way for 50+ years.

Generally only race engines with high viscosity oils do otherwise.

Factors such as crank and block rigidity are major reasons older engines would last longer with larger clearances.

RPM drives the rod bearing size and oil requirements. Many direct injection engines don't rev as high as engines from the recent past. Allowing smaller bearing diameters and the resulting tighter clearances.

 

[RDY4WAR]

Originally Posted by ka9mnx
Originally Posted by CR94
Interesting chart, RDY4WAR. Assuming the intermediate temperature range, it would've had put 0W-20 or 0W-10 in my 1981 Mazda, for which the service manual specified 0.0009" to 0.0017 clearance for mains.

Yes, interesting chart. That would work for your Mazda bearings but remember 40% of engine friction is in the liner, piston and ring area. It is also the most prone area of oil breakdown (viscosity loss). So it would probably be a bad idea for the ring/liner area.


The rings also operate in boundary and mixed lubrication, where the additive package has a far greater impact on wear and friction than the base oil.

 

[ZeeOSix]

Originally Posted by Cujet
That chart makes little sense with regard to rod bearings. The clearances quoted have little resemblance to any previous or common era conventional engines.


I believe the Ford Coyote 5.0L V8 has minimum rod clearance of 0.001", might even be a hair less. I'll look in the factory sevice manual and snip-it and post later.

 

[Mad_Hatter]

Originally Posted by RDY4WAR

The rings also operate in boundary and mixed lubrication, where the additive package has a far greater impact on wear and friction than the base oil.

Good point..+1.. this is where your EP addys come into play due to the temps/pressures.

 

[ka9mnx]

Originally Posted by Mad_Hatter
Originally Posted by RDY4WAR

The rings also operate in boundary and mixed lubrication, where the additive package has a far greater impact on wear and friction than the base oil.

Good point..+1.. this is where your EP addys come into play due to the temps/pressures.

The oil DOES operate at boundary lubrication with the designed oil. Running a lower grade oil puts the rings at TDC (thinned because of heat) in jeopardy

Analysis of Parasitic Losses in Heavy Duty Diesel Engines
by Christopher Joseph James
B.S. Mechanical Engineering
Northeastern University, 2010.

In this analysis a 50% reduction in lubricant viscosity predicted approximately 25% decrease in power cylinder friction.
It should be noted that a 50% reduction in lubricant viscosity would dramatically increase wear
rates in the power cylinder and would not be technically feasible without aggressive wear
mitigation strategies.

(Thanks Shannow)

 

[MetalSlug]

Made me want go back 0w20 instead of 5w30 on my i4 Honda Accord 2011

 

[RDY4WAR]

Originally Posted by ka9mnx
Originally Posted by Mad_Hatter
Originally Posted by RDY4WAR

The rings also operate in boundary and mixed lubrication, where the additive package has a far greater impact on wear and friction than the base oil.

Good point..+1.. this is where your EP addys come into play due to the temps/pressures.

The oil DOES operate at boundary lubrication with the designed oil. Running a lower grade oil puts the rings at TDC (thinned because of heat) in jeopardy

Analysis of Parasitic Losses in Heavy Duty Diesel Engines
by Christopher Joseph James
B.S. Mechanical Engineering
Northeastern University, 2010.

In this analysis a 50% reduction in lubricant viscosity predicted approximately 25% decrease in power cylinder friction.
It should be noted that a 50% reduction in lubricant viscosity would dramatically increase wear
rates in the power cylinder and would not be technically feasible without aggressive wear
mitigation strategies.

(Thanks Shannow)


This is assuming you're comparing base oils of similar pressure-viscosity coefficient and same additive package. Even when not, the experience with the high rpm alcohol engines I mentioned earlier showed little difference in wear with huge jumps in viscosity SAE 50 to 0w-3. The only area where wear was more apparent with the thinner oil was in the bearings. Reducing the ZDDP and MoDTC content by 20% had a much larger effect on wear of the rings and cylinders than the base oil viscosity. This was measured by tearing the engine down after 100 or so 1/4 mile passes, with oil changes every 25 passes, and accurately mic'ing everything. As a side note, Rotella T4 15w-40 (older CJ-4 formula) was run through these engines as well and 4 of the 16 cam lobes failed inspection after 100 passes due to loss of lobe lift. These engines are also running billet solid roller cams with over .900" valve lift and near 1,000 lbs of spring pressure which is well more than that oil was ever designed to withstand.

Another observation is that the wear rates were greater at lower oil temperature than higher, despite lower viscosity at higher temperature, which also indicates the additive package being a greater variable than viscosity as your anti-wear and friction modifier additives require heat to activate.

Think of it like sending an army into battle. You can send the most elite, well-trained men (base oil) into the fight, but if you don't give them weapons to fight with (additives), they're just cannon fodder.

 

[ka9mnx]

Duly noted but you are comparing a 1/4 mile engine to a grocery getter. Apples to oranges.

 

[Lowflyer]

Originally Posted by RDY4WAR
Reducing the ZDDP and MoDTC content by 20% had a much larger effect on wear of the rings and cylinders than the base oil viscosity.
Sorry. No. What gives you that idea?

 

[RDY4WAR]

Originally Posted by Lowflyer
Originally Posted by RDY4WAR
Reducing the ZDDP and MoDTC content by 20% had a much larger effect on wear of the rings and cylinders than the base oil viscosity.
Sorry. No. What gives you that idea?


The micrometers don't lie. It didn't matter what viscosity of oil was in the engine. The rings, pistons, and cylinders just didn't care. Same wear observed regardless of viscosity. Minor changes in the additive package had a much larger effect on cylinder wear than major jumps in viscosity. The only part of the engine that cared about the oil's viscosity were the bearings. That's a solid roller engine though. An engine with hydraulic lifters can be picky about viscosity depending on bleed down rates, and usually the issue is with too high viscosity rather than too low. Morel hydraulic lifters are a prime example. Anything above around 15 cSt and they tend to chatter.

 

[Lowflyer]

oil-club.de have a UOA of forgery, I mean, M1 5W-50. Looks like a mix of W60 und 75W-90

With a additives in the ballpark of 100 ZDDP (something like that). Yes, rofl.

Ok the driving profile was (fortunately) very unproblematic. And the wear values of UOA was not a big Wow... BUT, but it was also not disastrous (!) It was, I tell, medium of averages (UOAs).

Therefore ( who would have thought it?...): It is still and continue, the oil, that lubricate.
Base oil -> base, bedrock.
Addons -> adds. Useful, but not the bedrock.

 

[ZeeOSix]

Originally Posted by ZeeOSix
Originally Posted by Cujet
That chart makes little sense with regard to rod bearings. The clearances quoted have little resemblance to any previous or common era conventional engines.

I believe the Ford Coyote 5.0L V8 has minimum rod clearance of 0.001". I'll look in the factory sevice manual and snip-it and post later.


So I got around to looking up the main and rod clearances on the Ford Coyote 5.0L V8. As you can see they can be tight, around 0.001" minimum clearance. Even the piston to cylinder clearance can be pretty tight.

Even though the oil spec is 5W-20 for street use, Ford will recommend running 5W-50 for track use. So as usual, this shows that journal bearings (or other parts) clearance doesn't have much to do with what oil viscosity is specified for an engine.

 

[Cujet]

Originally Posted by ZeeOSix


So I got around to looking up the main and rod clearances on the Ford Coyote 5.0L V8. As you can see they can be tight, around 0.001" minimum clearance. Even the piston to cylinder clearance can be pretty tight.

Even though the oil spec is 5W-20 for street use, Ford will recommend running 5W-50 for track use. So as usual, this shows that journal bearings (or other parts) clearance doesn't have much to do with what oil viscosity is specified for an engine.





Yup, no different than engines from decades ago. The standard remains 0.0007 inches per inch of journal diameter, with 2 inch journals having as much as a 0.0005 inch leeway on the tight side, if desired. No magic there. As a general rule, trending towards the tight specification simply required excellent component structural stability at the expected loads, nothing more than that. While testing for Ford, we assembled engines to those specifications, 35+ years ago.

The performance engine builders that required "loose" clearances did so for reliability on structurally unsound equipment. Going "loose" was no faster, but it certainly was more reliable in some race situations.

 

[demarpaint]

Originally Posted by ZeeOSix
Originally Posted by ZeeOSix
Originally Posted by Cujet
That chart makes little sense with regard to rod bearings. The clearances quoted have little resemblance to any previous or common era conventional engines.

I believe the Ford Coyote 5.0L V8 has minimum rod clearance of 0.001". I'll look in the factory sevice manual and snip-it and post later.


So I got around to looking up the main and rod clearances on the Ford Coyote 5.0L V8. As you can see they can be tight, around 0.001" minimum clearance. Even the piston to cylinder clearance can be pretty tight.

Even though the oil spec is 5W-20 for street use, Ford will recommend running 5W-50 for track use. So as usual, this shows that journal bearings (or other parts) clearance doesn't have much to do with what oil viscosity is specified for an engine.

So much for the engines are being built so tight they "must" have a 20 grade oil in order to operate properly and not self destruct, as some allude to here.

 

[RDY4WAR]

Originally Posted by ZeeOSix
Originally Posted by ZeeOSix
Originally Posted by Cujet
That chart makes little sense with regard to rod bearings. The clearances quoted have little resemblance to any previous or common era conventional engines.

I believe the Ford Coyote 5.0L V8 has minimum rod clearance of 0.001". I'll look in the factory sevice manual and snip-it and post later.


So I got around to looking up the main and rod clearances on the Ford Coyote 5.0L V8. As you can see they can be tight, around 0.001" minimum clearance. Even the piston to cylinder clearance can be pretty tight.

Even though the oil spec is 5W-20 for street use, Ford will recommend running 5W-50 for track use. So as usual, this shows that journal bearings (or other parts) clearance doesn't have much to do with what oil viscosity is specified for an engine.

They are also assuming the street will see 200-220*F oil temps and the track will see >260*F oil temps. If you were to plot the viscosity, the KV150 of the 15w-50 would be pretty close to the KV100 of the 5w-20. Temperature is the other part of that equation that must be considered.

NHRA Pro Stock engines have rod and main bearing clearances around .0028-.0032" and use 0w-2/3 oil because their oil temp is 100-130*F.