Engine Oil HTHS (High Temperature High Shear) Specifications

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Engine Oil HTHS (High Temperature High Shear) Specifications

June 05, 2025, 08:15:43 am

My cousin who was a Porsche mechanic for years sent me the below Duramax discussion on engine wear damage due to the HTHS values in US manufactures oils. Shear pertains to how well the oil holds up to lubrication between metal surfaces in high heat. The focus was on the high shear value being too low @ 2.5 in some US oil manufacturers. This value helps to increase mileage but at the cost of engine wear. The European shear values are at 3.5 which mileage suffers but engine wear is vastly improved. This is the problem with those low viscosity oils recommended by the US vehicle manufactures such as or similar to 0W-20 and 0W-30. Here is what my cousin sent to me:

Ford 7.3 Godzilla Engine
I looked up the specifications for the 7.3 gas motor. Ford states 5w-30 Synthetic blend but according to various tech websites, Ford also states that you can use full synthetic. The 5w oil is to help meet fuel economy standards from what I have read.
Your motor will be pulling close to full weight all the time and running a 5w-30 oil would make me a little nervous climbing the Rockie Mountains with those long steep grades.
I noticed in Walmart today that they carry Castrol Edge 5w-30 Euro and 5w-40 Euro full synthetic which meets Porsche C40 .
They also carry 5w-40 Mobil 1 full synthetic. Shell Rotella also has a 5w-40 diesel oil that according to Shell, can be used in gas or diesel.

You need to use what you feel comfortable using but as long as you stick to a European spec oil with the higher HTHS rating, I think you will be fine.
Amsoil and Shaeffers as well as Mobil 1 EUROPEAN SPEC (ESP)
European spec oils have a higher HTHS, you want a minimum of 3.5 HTHS
HTHS- high temperature high shear
Oils to consider
Mobil 1 5w-30 ESP HTHS 3.5
Mobil 1 0w-40 Super Car ( Corvette oil ) HTHS 3.5
Amsoil 0w-40 for gas engines HTHS 3.5 (cars)

****Amsoil 0w-40 Max Duty HTHS 4.2 gas and diesel trucks...this would be my choice

If you decide to run a 5w-30, then you want a c3 oil, not a c2 or c1
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I post this here mainly for your awareness and discussion.
Mike C

Re: Engine Oil HTHS (High Temperature High Shear) Specifications

Reply #1 – June 05, 2025, 11:53:16 am

Interesting topic.
Euro-spec oils are fine for use in gas engines.
The discussion above pertains to diesel engines, a wholly different breed of engine.
Diesel engines produce much more torque, particularly impacting the rod bearings with much higher pressures, repeated thousands of times a minute..

Do Euro oils provide better protection for gas engines? We would need the advice of experienced engine design engineers. On the Jeep sites I frequent, I see similar postings from many"experts" wanting everyone to switch to heavier oils and/or Euro oils. Everyone is an expert on the internet.
If wanting to test the two types of oils, the only method I see available to us mortals is using an oil analysis to see if one produces fewer wear products.
Blackstone Labs
Oil Analysis | Blackstone Laboratories

Larry

Re: Engine Oil HTHS (High Temperature High Shear) Specifications

Reply #2 – June 05, 2025, 05:34:09 pm

I am curious what about engine oil weight should be used in the Ford 6.8 liter V-10. Our 2003 model year has the recommendation for synthetic blend 5w20. I have head that later years called for synthetic blend 5w30. I seem to recall that Larry W used to say the engineers who designed these engines knew best what we should use but I seem to think the suggested oil changed over the years.

Larry, your rig had a 2003 engine the same as mine. Then you got a remanfactured engine and later a 3rd engine. So what oil weight are you using?

For the record, I continue to use full synthetic 5w20 and I have been using Penzoil Platinum for over a decade. We now have over 140,000 miles on it and have not found I need to add oil between changes. I was thinking about switching the the "High Mile" version of the same oil but have been reluctant to change my methodology.

Steve K

Re: Engine Oil HTHS (High Temperature High Shear) Specifications

Reply #3 – June 05, 2025, 09:22:16 pm

Quote from: Steve K. - June 05, 2025, 05:34:09 pm

I am curious what about engine oil weight should be used in the Ford 6.8 liter V-10. Our 2003 model year has the recommendation for synthetic blend 5w20. I have head that later years called for synthetic blend 5w30. I seem to recall that Larry W used to say the engineers who designed these engines knew best what we should use but I seem to think the suggested oil changed over the years.

Larry, your rig had a 2003 engine the same as mine. Then you got a remanfactured engine and later a 3rd engine. So what oil weight are you using?

For the record, I continue to use full synthetic 5w20, and I have been using Penzoil Platinum for over a decade. We now have over 140,000 miles on it and have not found I need to add oil between changes. I was thinking about switching the the "High Mile" version of the same oil, but have been reluctant to change my methodology.

I now run 5w-30 Mobil 1, switching from the 5w-20 that was originally required when Ford upgraded to 5w-30 for the V10s. I wouldn't hesitate to run 10w-30 in the summer.

Several years ago, Joan Taylor had an oil analysis done on her 2003 T/KL at 120,000 miles with Blackstone. The report showed an excellent wear analysis and indicated the 5000-mile change interval was fine and could have gone longer. This was using Ford's semi-synthetic 5W-20 oil exclusively.

The High Mileage version of Mobil 1 has more of the additives that are used while driving, enabling longer oil change intervals.

I have mentioned before about a long-term oil analysis we ran at LAX 20 years ago on a wide sampling of its large fleet of trucks, cars, and heavy equipment between normal, dino oil, vs Mobil 1 synthetic. The results showed normal oil was good for 7000 mile change intervals and synthetic for over 10,000 miles.
Not wanting vehicles to stay out in the field for extremely long periods without being fully checked out, a 7000-mile change interval with normal, non-synthetic oils was selected, except for engines where synthetics were required by the manufacturers.

Larry

Re: Engine Oil HTHS (High Temperature High Shear) Specifications

Reply #4 – June 05, 2025, 09:58:51 pm

Thanks for the information Larry!

Re: Engine Oil HTHS (High Temperature High Shear) Specifications

Reply #5 – June 06, 2025, 12:29:19 am

Quote from: Steve K. - June 05, 2025, 09:58:51 pm

Thanks for the information Larry!

If you want to spend a lot of time reading about what others think about engine oil, the premier engine oil site is 'Bob the Oil Guy" .
https://bobistheoilguy.com/forums/
Have fun.

Larry

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