...in fact I'm now using 0W30 Amsoil in my LS2. 
oil weight
Pro
Joined: Dec 2007
Posts: 633
Likes: 26
From: Montgomery Alabama
St. Jude Donor '09
I believe that GM got it right when the designed the engine and chose the 5w oil to go in it.
Safety Car
Joined: May 2006
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From: Providence Forge, VA
St. Jude Donor '08-'09-'10-'11-'12
Race Director
Joined: Jul 2004
Posts: 16,795
Likes: 62
From: Lake Havasu City, AZ
Yes...
5W30 flows better at start-up because it has a lower intrinsic viscosity .
BUT it has viscosity index improvers(VII) that make it thicken to a 30 weight oil (exactly like at 10W30 does) at operating temperatures.
This means at operating temperature ther is no difference in performance BUT at start-up 5W30 gets oil to all areas of your engine faster than 10W30 does.. so it provides better lubrication on start-up and the same lubrication while operating...
5W30 flows better at start-up because it has a lower intrinsic viscosity .
BUT it has viscosity index improvers(VII) that make it thicken to a 30 weight oil (exactly like at 10W30 does) at operating temperatures.
This means at operating temperature ther is no difference in performance BUT at start-up 5W30 gets oil to all areas of your engine faster than 10W30 does.. so it provides better lubrication on start-up and the same lubrication while operating...
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Drifting
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From: Upper St. Clair PA
St. Jude Donor '06-'07-'09
Le Mans Master
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From: Thousand Oaks California
HOOK-EM HORNS
Joined: Aug 2006
Posts: 3,517
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From: Port Aransas, Texas Tx
St. Jude Donor '08
I called one of my local dlr's, capital chevy in Austin, and the service adv. stated that they put 10-30 in a lot during the summer so I tried it. NO MORE. The oil sensor went to 70 percent life left when I first started it and in less than 3K miles was showing only 20 percent oil life left. It seemed to reduce my power a little but that might have been that I was not happy with the new oil after I changed it.
Instructor
Joined: Nov 2006
Posts: 210
Likes: 0
From: Columbus IN
After my H/C package at DTE they put 10W-30 in. I asked why and Phil responded it's better protection at the increased redline. Phil's in his 30s I'd guess so he's not from my era when you had summer oil and winter oil. I'm sticking with his recommendation since he's the warranty.
Race Director
Joined: Jul 2004
Posts: 16,795
Likes: 62
From: Lake Havasu City, AZ
DEV-06C6
There has been a lot of debate of oil for those with H/C packages.
That debate has centered on which API service classification of oil to use versus which weight.
The issue is an anti-wear additive called zinc di-thio phospate which is a fantastic anti-wear compound BUT impacts catalyst life on Japanese built car technology. Japanese manufacturers were having high warrarny failure rate of emmissions systems. When API went to the SM classification about a year ago, they conceded to EPA's requested removal of ZDTP.
So the newest oils are service classification SM (Mobil 1 included). They do not contain ZDTP. A lot of engine builders/performance shops are now recommending the usage of older technlogy ZDTP oils. Those can be found in commerical oil grades that are designed for mixed fleet operations like trucking companies that want one oil to cover the salesman's car and the big rig...
Products like Shell Rotella T synthetic and Mobil Delo still are not SM and thus still contain ZDTP. So to protect your warranty ask Phil for his recommendation of API service classification along with oil weight.
There has been a lot of debate of oil for those with H/C packages.
That debate has centered on which API service classification of oil to use versus which weight.
The issue is an anti-wear additive called zinc di-thio phospate which is a fantastic anti-wear compound BUT impacts catalyst life on Japanese built car technology. Japanese manufacturers were having high warrarny failure rate of emmissions systems. When API went to the SM classification about a year ago, they conceded to EPA's requested removal of ZDTP.
So the newest oils are service classification SM (Mobil 1 included). They do not contain ZDTP. A lot of engine builders/performance shops are now recommending the usage of older technlogy ZDTP oils. Those can be found in commerical oil grades that are designed for mixed fleet operations like trucking companies that want one oil to cover the salesman's car and the big rig...
Products like Shell Rotella T synthetic and Mobil Delo still are not SM and thus still contain ZDTP. So to protect your warranty ask Phil for his recommendation of API service classification along with oil weight.