- Joined
- Dec 20, 2020
- Messages
- 298
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
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