Viscosity & CAFE Q&A w Corvette Development Team Leader

[Robvette]

I asked Russ Craighead, who led the Corvette development team for GM, through the C5 and C6 programs, and Russ also owned four C4s.

Question: Hey Russ, here’s a quick question that of the people I know - you may be able to answer.

When my 92 Corvette came home from being built by Lingenfelter, they put 10W-40 oil in it. When Calaway modified C4 Corvettes, they would fill them with Mobil 1 15W-50.

The owners manual in my 89 (and all the other years of the C4 too) specify 5W-30, and energy conserving seems to be the emphasis.

Some believe that the 5W-30 recommendation was chosen to help achieve CAFE* fleet fuel economy targets for GM, and it protects the engine sufficiently, but not optimally.

If engine protection, performance and longevity are top priorities then it seems 10w40 or 15w50 would have been recommended by GM.

Does that seem accurate?

In later model Corvettes, GM seemed to address this by saying in the owners manual 5w30, and “if going to the track then use 15w50”. Essentially meeting CAFE *and* instructing owners to use a viscosity that protects better when needed most.

Answer: “Yep. With government and corporate emphasis on fuel economy, lower viscosity was tested and recommended. Like Lingenfelter, I used somewhat higher viscosity in my personal Vettes.” ~ Russ Craighead

*CAFE = corporate average fuel economy

 

[Pelican]

I asked Russ Craighead, who led the Corvette development team for GM, through the C5 and C6 programs, and Russ also owned four C4s.

Question: Hey Russ, here’s a quick question that of the people I know - you may be able to answer.

When my 92 Corvette came home from being built by Lingenfelter, they put 10W-40 oil in it. When Calaway modified C4 Corvettes, they would fill them with Mobil 1 15W-50.

The owners manual in my 89 (and all the other years of the C4 too) specify 5W-30, and energy conserving seems to be the emphasis.

View attachment 176023

Some believe that the 5W-30 recommendation was chosen to help achieve CAFE* fleet fuel economy targets for GM, and it protects the engine sufficiently, but not optimally.

If engine protection, performance and longevity are top priorities then it seems 10w40 or 15w50 would have been recommended by GM.

Does that seem accurate?

In later model Corvettes, GM seemed to address this by saying in the owners manual 5w30, and “if going to the track then use 15w50”. Essentially meeting CAFE *and* instructing owners to use a viscosity that protects better when needed most.

Answer: “Yep. With government and corporate emphasis on fuel economy, lower viscosity was tested and recommended. Like Lingenfelter, I used somewhat higher viscosity in my personal Vettes.” ~ Russ Craighead

*CAFE = corporate average fuel economy

I've ALWAYS said that the owner's manual is a "Compromise" between what the engineers want and what the marketing Dept wants, now one can also add what CAFE wants. What oil is best depends on the use, for most buyers perhaps 5W30 is sufficient enough not to cause immediate or middle term damage, but if you press it and drive in a spirited manner or even race, that would not be enough especially long-term. That's why they move up to 10-15W40-50 also they are not concerned with cold weather starting in this situation.

 

[buster]

The current gen M1 Supercar 0w40 was designed for daily driving and track use. HT/HS of 3.53 and it sits right on the 30/40 grade line.

 

[Cujet]

Having done hundreds of dyno runs for OEM and race engines and decades of racing, it became quite clear to me that in conventional engines, oil temperature matters more than just about anything else. OEM's don't often do anything to address high oil temps in severe conditions, and racers sometimes get it right. In high boost engines, with connecting rod-shortening levels of pressure, adequate viscosity is a must. Remember, there is a reason that robust oils for hard working engines nearly always have an HTHS above 3.5. Generally 3.8 or higher. Quite simply, an oil that provides adequate viscosity at high temperatures is a very good thing, when things get tough.

We can race with 0W-16, with a few requirements. Oil temp is maintained at a low number, sump capacity is adequate, flow rates are high, and rod bearing sizes are adequate. Think about that for a minute and it becomes quite clear why some high performance engines can't use Wesson motor oil (a little joke). If one is road racing a 450HP 2.6L NA engine with 1.5" bearing journals, and expect the engine to last a few seasons, we might want to choose a 50 viscosity oil.

 

[DirectRejection]

Having done hundreds of dyno runs for OEM and race engines and decades of racing, it became quite clear to me that in conventional engines, oil temperature matters more than just about anything else. OEM's don't often do anything to address high oil temps in severe conditions, and racers sometimes get it right. In high boost engines, with connecting rod-shortening levels of pressure, adequate viscosity is a must. Remember, there is a reason that robust oils for hard working engines nearly always have an HTHS above 3.5. Generally 3.8 or higher. Quite simply, an oil that provides adequate viscosity at high temperatures is a very good thing, when things get tough.

We can race with 0W-16, with a few requirements. Oil temp is maintained at a low number, sump capacity is adequate, flow rates are high, and rod bearing sizes are adequate. Think about that for a minute and it becomes quite clear why some high performance engines can't use Wesson motor oil (a little joke). If one is road racing a 450HP 2.6L NA engine with 1.5" bearing journals, and expect the engine to last a few seasons, we might want to choose a 50 viscosity oil.

Well, after all, Toyota did jump all the up to 0W20 on Corolla GR.

BTW I use only highest quality very thin oil.

Any thoughts on Red Line High Performance 5W30 for Vettes ? HTHS 3.7 . Highest quality ingredients. Albeit just below the 3.8 threshold.

Of course most would want head room, but I am trying to get at the demarcation point, considering particulars of oils beyond viscosity alone.

 

[Robvette]

The current gen M1 Supercar 0w40 was designed for daily driving and track use. HT/HS of 3.53 and it sits right on the 30/40 grade line.

Also

 

[Lavrishevo]

Good article on the subject

Motor Oils - Fuel Economy vs. Wear

Conventional wisdom states that engine oils that increase fuel economy allow less friction and prolong engine life. The purpose of this article is to challenge conventional wisdom, particula…

www.machinerylubrication.com

 

[DirectRejection]

I am still waiting for someone to convince me the M1 SuperCar 5W50 offers superior performance and significantly better protection than Red Line High Performance 5W30.

 

[edyvw]

I am still waiting for someone to convince me the M1 SuperCar 5W50 offers superior performance and significantly better protection than Red Line High Performance 5W30.

Generally it is bumped to have certain grade for duration of OCI. BMW was using 10W60 bcs. it would shear fairly fast to 50 grade and stay there.
Higher viscosity provides better pressure stability.
My point is that depends on application, type of use: street, track or race, or bit of street and a lot of track, or a lot of street and few track days a year. And it depends on UOA.

 

[DirectRejection]

Generally it is bumped to have certain grade for duration of OCI. BMW was using 10W60 bcs. it would shear fairly fast to 50 grade and stay there.
Higher viscosity provides better pressure stability.
My point is that depends on application, type of use: street, track or race, or bit of street and a lot of track, or a lot of street and few track days a year. And it depends on UOA.

I am still trying to ascertain the HTHS.
I see it is SP, but not catalytic converter compatible like the 0W40. And it's mid SAPS. OCI anyone ?

 

[edyvw]

I am still trying to ascertain the HTHS.
I see it is SP, but not catalytic converter compatible like the 0W40. And it's mid SAPS. OCI anyone ?

I am not sure what is the deal with Supercar considering there is Euro lineup.

 

[DirectRejection]

I am not sure what is the deal with Supercar considering there is Euro lineup.

That's it. I am going with HPL Euro 10W30. HTHS 3.652. This driver is not crazy about wide range, 5W50 or 10W60.

 

[buster]

I am still waiting for someone to convince me the M1 SuperCar 5W50 offers superior performance and significantly better protection than Red Line High Performance 5W30.

I couldn't tell you, but to me I put value into the testing that is done with the product. That seems to be what they're saying here in this article. Marketing for sure but XOM tested Supercar 0w40 for 2 years with GM.

Red Line looks the best oil on the planet when you look at their data sheets, but UOA's show otherwise.

Site Maintenance

 

[edyvw]

That's it. I am going with HPL Euro 10W30. HTHS 3.652. This driver is not crazy about wide range, 5W50 or 10W60.

What is oil for?

 

[DirectRejection]

What is oil for?

Protection + performance.

GF-7 is going to be stricter on SAPS.

The noose will tighten.

CAFE vs higher grades.

 

[edyvw]

Protection + performance.

GF-7 is going to be stricter on SAPS.

The noose will tighten.

CAFE vs higher grades.

I was thinking you are looking for specific stuff.
I really don’t pay attention to it. I ran in Toyota M1 0W40 sometimes. It was gas pig either way.
I get this argument that when you take into consideration how much it saves fuel on millions of cars, it is actually substantial number. But, at the same time it seems all gains in fuel economy went to upsize SUV’s. Kind of people are set with certain mpg, SUV has it, go get it. It would be better if we found a way to downsize vehicles a bit.

 

[gfh77665]

In later model Corvettes, GM seemed to address this by saying in the owners manual 5w30, and “if going to the track then use 15w50”. Essentially meeting CAFE *and* instructing owners to use a viscosity that protects better when needed most.

Answer: “Yep. With government and corporate emphasis on fuel economy, lower viscosity was tested and recommended. Like Lingenfelter, I used somewhat higher viscosity in my personal Vettes.” ~ Russ Craighead

100%.

 

[Cujet]

I am still waiting for someone to convince me the M1 SuperCar 5W50 offers superior performance and significantly better protection than Red Line High Performance 5W30.

It is not likely to happen. In fact, the boutique oils may be just a touch on the "more robust" side of the specs, more shear stable, and will likely provide all the protection needed.

 

[DirectRejection]

@edyvw
@Cujet
et al

This is what I am trying to get at, as you seem to reference...

With a Corvette, why limit yourself to these SP requirements ?

With street and track usage, why have any sort of "ESP" line thinking ?

I am thinking about protecting this Corvette engine and getting performance out of it, over emmissions and emmission system components.

IDK. There are definitely people who insist on strictest compliance with these labels, SP, DEXOS R and ESP, but these boosted oils would be of great interest, in my book.

 

[DirectRejection]

Jeesh.
Semantics.
Lawyers.
"Adequate"
vs
"Optimum."