Highest HTHS oils available, taking into account shear stability

[Cujet]

All about the highest HTHS oils available, not concentrating on motorycles oils specifically, however, MC oils do tend to be high up on the list. My experience is very positive with M1's 20W-50 V-Twin oil in turbocharged race cars.

A friend with a KTM recently asked me about the most robust oils available. I suggested M1, V-Twin 20W-50 due to the superb resistance to shear and the high HTHS, which by memory is 5.9, and it is believed to be free of VII's too! Redline 20W-50 Motorcycle oil has a published HTHS of 6.1 along with similarly excellent ZDDP levels (2200/2000). The Redline might be the highest (published) HTHS 20-50 oil commonly available.

One would have to go to Amsoil racing 60 (25.0 at 100ºC) to find what I think is the absolute highest HTHS, and the specs seem to show a stunning 7.7!

Castrol Edge Supercar 10W-60 has an HTHS now said to be 5.6–5.8, (down from 6.1) and similar 10W-60 motorcycle oils are also in this range. Although with VII's the 10W-60's tend to shear fast and I don't trust the high HTHS specs to hold up for any length of time. KTM's forged chocolate camshaft wear problems might back this up.

By way of comparison, M1 15W-50 has an HTHS of 4.5. It has been a favorite of mine for OPE and turbocharged cars, as it is not a particularly viscous oil, and does exceedinly well when stepping up from a straight 30 or 10W-30/40, especially for air cooled engines. The 15W-50 falls short on brutal track days in some engines (that I may or may not have been involved with...) , when oil temps are not well controlled. An example might be during a Florida track day in a stock twin turbo V6, or even my past Turbo Honda S-2000 with 400HP and no oil cooler.

• Mobil 1 20W-50 V-Twin: 5.9 cP
• Red Line 20W-50: ~5.5–5.8 cP (with the motorcycle version showing a published 6.1)
• Amsoil V-Twin 20W-50: ~5.6 cP; Dominator 20W-50: 5.5 cP (estimated)
• Motul 300V 15W-50: 5.33 cP
• Ravenol RSS 10W-60: 5.7 cP
• HPL Euro 10W-60: ~5.5+ cP (estimated)
• Castrol Edge 10W-60: 5.6–5.8 cP, possibly 6.0 cP historically, but not now.
• Highest worldwide: Straight SAE 60, Amsoil 7.7

 

[kschachn]

• Highest worldwide: Straight SAE 60, Amsoil 7.7

Which out of your list would fit the title of the thread. That would be completely shear stable.

 

[BrendanC]

may try some 15w-50 for my accord next OCI to see if it won’t burn as bad. thanks for the information.

 

[Cujet]

Which out of your list would fit the title of the thread. That would be completely shear stable.

Both M1 and Redline 20W-50 motorcycle oils meet the 'top dog' requirement. I'm not at all sure they are different. It is very likely that Amsoil is also 'top dog' here with regard to shear. But the published HTHS is 5.6, a bit lower.

 

[kschachn]

Both M1 and Redline 20W-50 motorcycle oils meet the 'top dog' requirement. I'm not at all sure they are different.

Only different in whether they contain VM or not. Of course some VII are more stable than others but if you want absolute shear stability then a monograde is the way to go.

 

[Cujet]

Only different in whether they contain VM or not. Of course some VII are more stable than others but if you want absolute shear stability then a monograde is the way to go.

As I understand it, the 20W-50 Amsoil, M1 and Redline motorcycle oils contain no VII's. By comparison, the 5-50's and 10W-60's traditionally all did (maybe there is one now Ravenol 10W-60 that does not).

An example of a KTM 790 camshaft. Often operated on 10W-60 oil. The fact that the cam is manufactured from drop forged and heat treated chocolate has no bearing on it's rapid wear. It's the oil's fault.... (just kidding of course) It is anybody's guess whether more robust oil would help here.

 

[Cujet]

may try some 15w-50 for my accord next OCI to see if it won’t burn as bad. thanks for the information.

It will run just fine in your accord. I used it in my S2000 turbo with fantastic results.

 

[kschachn]

As I understand it, the 20W-50 Amsoil, M1 and Redline motorcycle oils contain no VII's. By comparison, the 5-50's and 10W-60's all do.

Could be. If they don’t then they could be labeled as a monograde as well, it’s up to the blender how they are labeled. They can put either one or both per the SAE rules.

 

[chris719]

Ravenol RSS is 6.4 now. Castrol Edge 10W-60 is 5.2 based on the last datasheet where the value was published. Ravenol claims the new RSS contains no VM but that could be a translation thing.

Due to the special mixture of synthetic, highly polar Group V base oils with a high proportion of high and low viscosity PAO, it could be formulated without the use of viscosity index improvers.

 

[RevvCats]

Those are all thick out of the bottle but sheer stability, especially HTHS stability since most labs don’t even offer that test as an add on, is another question

LSjr tested a few off the shelf oils a while ago at HPL and HTHS sheered pretty significantly right along with the kinematic viscosity at 100C. Only four oils to draw conclusions from but if any of those oil you listed are known to sheer their KV100 down then their HTHS is probably pooping the bed too.

 

[Kalle.J]

may try some 15w-50 for my accord next OCI to see if it won’t burn as bad. thanks for the information.

You are probably joking.
But anyway don't bother, I tried 5W50 in the D16z5 DOHC Honda Crx way back when.
Just felt like it lost a couple HP.

 

[Cujet]

Ravenol RSS is 6.4 now. Castrol Edge 10W-60 is 5.2 based on the last datasheet where the value was published. Ravenol claims the new RSS contains no VM but that could be a translation thing.

Ohhhh, nice!!! Although traditionally all of the 10W-60's contained VII's and shear fast. A 10W-60 without VII's and a stunningly high HTHS would be a relatively new 'thing'

 

[Cujet]

You are probably joking.
But anyway don't bother, I tried 5W50 in the D16z5 DOHC Honda Crx way back when.
Just felt like it lost a couple HP.

For specific problems, the 15W-50 will work quite well in Honda engines. That feeling you are talking about is unlikely on an engine with weak ring seal. The higher viscosity can sometimes result in better ring seal and more efficiency/power.

 

[Kennedy01]

What is the HTHS on 70 weight racing oil like Driven GP-1 or Redline?

 

[BrendanC]

You are probably joking.
But anyway don't bother, I tried 5W50 in the D16z5 DOHC Honda Crx way back when.
Just felt like it lost a couple HP.

not joking, the car eats oil for breakfast. it needs valve stem seals.

 

[DV0993]

It will run just fine in your accord. I used it in my S2000 turbo with fantastic results.

Any thoughts on Mobil 5w50? I have plenty of it, but tend to run 5w40 race oils in my s2000 (no burning)

 

[FCD]

Valvoline VR1 20W50 conventional is around 5.0 iirc.
I've used it several times, definitely made a difference on the oil pressure.
Sadly where i live it's become too expensive so i don't buy it anymore, something like 45€ / 5L

 

[Cujet]

Any thoughts on Mobil 5w50? I have plenty of it, but tend to run 5w40 race oils in my s2000 (no burning)

If you have it, try it. While the 5W-50 is known to shear, it may be worlds better in your engine than the required 0W-water viscosity.

 

[RaymondP]

By way of comparison, M1 15W-50 has an HTHS of 4.5. It has been a favorite of mine for OPE and turbocharged cars, as it is not a particularly viscous oil, and does exceedinly well when stepping up from a straight 30 or 10W-30/40, especially for air cooled engines. The 15W-50 falls short on brutal track days in some engines (that I may or may not have been involved with...) , when oil temps are not well controlled. An example might be during a Florida track day in a stock twin turbo V6, or even my past Turbo Honda S-2000 with 400HP and no oil cooler.

Have been using M1 FS 15W50 since I acquired my low mileage new to me 2013 Triumph Thruxton air-cooled parallel twin that runs hot in the summer months. In 2023 I completed the valve/cam check and switched out the shims to bring it back into spec. Not way out of spec. but now safely in the middle of the range. For what it's worth, on inspection engine has remained very clean and bike continues to run well.

 

[kschachn]

Those are all thick out of the bottle but sheer stability, especially HTHS stability since most labs don’t even offer that test as an add on, is another question

LSjr tested a few off the shelf oils a while ago at HPL and HTHS sheered pretty significantly right along with the kinematic viscosity at 100C. Only four oils to draw conclusions from but if any of those oil you listed are known to sheer their KV100 down then their HTHS is probably pooping the bed too.

But also, mechanical shear (not sheer) of the VM is highly dependent on the engine. Most engines do not place high shear loads on the oil, but some might. In those results you posted, the no-VII result shows the margin of error for the test.