Engine oil question.
Thread Starter
Racer
Joined: Nov 2005
Posts: 404
Likes: 0
From: KY
Engine oil question.
This is probably a stupid question, but here goes. Last time I got my oil changed I let a local shop do it that I often deal with. Instead of using the typical 5w30 synthetic they used the 10w30 synthetic. Which they told me afterwards. At the time I didn't really think to much about it and just assumed it would be alright. I've driven it a few hundred miles and haven't noticed anything funky. I was just curious if anybody else here uses 10w30? :o
P.S. Any other car and I probably wouldn't care, but I try to be extra careful with my Vette.
P.S. Any other car and I probably wouldn't care, but I try to be extra careful with my Vette.
Race Director
Joined: Nov 2003
Posts: 12,346
Likes: 5
From: Mustang OK
Per your owner's manual and the GM Service Manual, you may use SAE 10W-30 if it’s going to be 0°F (-18°C) or above and the oil meets GM Standard 4718M.
Here's what the 2003 Owner's Manual says. Yours should read much the same:
Following from the 2003 Corvette Owner's Manual, Section 5, Service and Appearance Care:
Hope this helps! 
Here's what the 2003 Owner's Manual says. Yours should read much the same:
Following from the 2003 Corvette Owner's Manual, Section 5, Service and Appearance Care:
What Kind of Engine Oil to Use
Look for two things:
Oils meeting these requirements should also have the starburst symbol on the container. This symbol indicates that the oil has been certified by the American Petroleum Institute (API). You should look for this on the oil container, and use only those oils that are identified as meeting GM Standard 4718M and have the starburst symbol on the front of the oil container. Your vehicle’s engine is filled at the factory with a Mobile 1® synthetic oil. which meets all requirements for your vehicle.
Substitute Engine Oil: When adding oil to maintain engine oil level, oil meeting GM Standard GM4718M may not be available. You can add substitute oil designated SAE 5W-30 with the starburst symbol at all temperatures. If temperatures are above 0°F (-1 8°C), you may substitute SAE 10W-30 with the starburst symbol. Substitute oil not meeting GM Standard GM4718M should not be used for an oil change.
Engine Oil Additives
Don't add anything to your oil. The recommended oils with the starburst symbol are all you will need for good performance and engine protection.
Look for two things:
- GM4718M
Your vehicle’s engine requires a special oil meeting GM Standard GM4718M. Oils meeting this standard may be identified as synthetic. However, not all synthetic oils will meet this GM standard. You should look for and use only an oil that meets GM Standard GM4718M.
Notice: If you use oils that don’t have the GM4718M Standard designation, you can cause engine damage not covered by your warranty.
- SAE 5W-30
As shown in the viscosity chart, SAE 5W-30 is best for your vehicle. However, you can use SAE 10W-30 if it’s going to be 0°F (-18°C) or above. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils such as SAE 20W-50.
Oils meeting these requirements should also have the starburst symbol on the container. This symbol indicates that the oil has been certified by the American Petroleum Institute (API). You should look for this on the oil container, and use only those oils that are identified as meeting GM Standard 4718M and have the starburst symbol on the front of the oil container. Your vehicle’s engine is filled at the factory with a Mobile 1® synthetic oil. which meets all requirements for your vehicle.
Substitute Engine Oil: When adding oil to maintain engine oil level, oil meeting GM Standard GM4718M may not be available. You can add substitute oil designated SAE 5W-30 with the starburst symbol at all temperatures. If temperatures are above 0°F (-1 8°C), you may substitute SAE 10W-30 with the starburst symbol. Substitute oil not meeting GM Standard GM4718M should not be used for an oil change.
Engine Oil Additives
Don't add anything to your oil. The recommended oils with the starburst symbol are all you will need for good performance and engine protection.
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 243
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Originally Posted by rws.1
At operating temperatures there is no difference in protection afforded by either 10W30 or 5 W30.
The question is ,did they use a synthetic 10W30 that meets GM4718M ?
As long as it's a full synthetic like Mobil 1, Amsoil, etc. you're good to go.
Premium Supporting Vendor
Joined: Aug 2001
Posts: 5,364
Likes: 38
From: King George VA
Originally Posted by phoenixfoundmac
...Instead of using the typical 5w30 synthetic they used the 10w30 synthetic.
__________________
C66 Racing #66 NASA ST2, SCCA T2
AMSOIL Dealer (Forum Vendor)
AMSOIL Preferred Customer Program (Members buy at Wholesale - a savings of about 25%)
C66 Racing #66 NASA ST2, SCCA T2
AMSOIL Dealer (Forum Vendor)
AMSOIL Preferred Customer Program (Members buy at Wholesale - a savings of about 25%)
Intermediate
Joined: Feb 2006
Posts: 30
Likes: 0
From: Naples Fl
I just had my oil changed at my local dealer and when I looked at the receipt it showed Mobil 1 10W30. I questioned the service tech and he advised they used it because of the Florida heat. I told him that I had 5W30 for adding when needed and he had advised they could be mixed with no problem. Should be OK if the dealership used it, right?
Race Director
Joined: Dec 2000
Posts: 19,304
Likes: 85
From: San Diego CA
I'd say so, but you might want to explain to those guys next time that it's the second number that determines the high temperature protection. Thus, even a 0W-30 protects as well as a 10W-30 under high heat conditions. The difference between the two is that the 0W-30 or 5W-30 oil flows more easily at startup - yes, even when startup is at 80 degreesF. Over the very long run, less wear at startup means longer engine life. Granted, this may mean that instead of getting 150,000 miles out of your LS1, you'd get 250,000 miles, so your choice of oil might be based upon how long you intend to keep your vehicle.
Premium Supporting Vendor
Joined: Aug 2001
Posts: 5,364
Likes: 38
From: King George VA
Originally Posted by HeatLtC6
I just had my oil changed at my local dealer and when I looked at the receipt it showed Mobil 1 10W30. I questioned the service tech and he advised they used it because of the Florida heat. I told him that I had 5W30 for adding when needed and he had advised they could be mixed with no problem. Should be OK if the dealership used it, right?
To add to the discussion mentioned by Dave, one reason to use a 10w30 over a 5w30 is that a 10w30 will require fewer viscosity improver's (VI) to attain its smaller viscosity spread. Thus, in general, a 10w30 will have a higher High Temp High Shear (HTHS) rating than its 5w30 counterpart. Additional, with fewer VIs, the oil is less likely to shear low out of grade, e.g. a 5w30 can shear down to a 5w20. As an example, according to Mobil 1's website, the HTHS rating of their 5w30 is 3.09 and the HTHS of the 10w30 is 3.14. So to some extent your dealership is correct, you get slightly better high temp protection with the 10w30. How much that is offset by increased wear due to high viscosity when cold is hard to say.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Instructor
Joined: Apr 2001
Posts: 212
Likes: 0
From: Northern California
Originally Posted by Subdriver
Mobil 1 10w30 meets GM Standard 4718M, but Mobil 1 Extended Performance 10w30 does not for some reason.
To add to the discussion mentioned by Dave, one reason to use a 10w30 over a 5w30 is that a 10w30 will require fewer viscosity improver's (VI) to attain its smaller viscosity spread. Thus, in general, a 10w30 will have a higher High Temp High Shear (HTHS) rating than its 5w30 counterpart. Additional, with fewer VIs, the oil is less likely to shear low out of grade, e.g. a 5w30 can shear down to a 5w20. As an example, according to Mobil 1's website, the HTHS rating of their 5w30 is 3.09 and the HTHS of the 10w30 is 3.14. So to some extent your dealership is correct, you get slightly better high temp protection with the 10w30. How much that is offset by increased wear due to high viscosity when cold is hard to say.
To add to the discussion mentioned by Dave, one reason to use a 10w30 over a 5w30 is that a 10w30 will require fewer viscosity improver's (VI) to attain its smaller viscosity spread. Thus, in general, a 10w30 will have a higher High Temp High Shear (HTHS) rating than its 5w30 counterpart. Additional, with fewer VIs, the oil is less likely to shear low out of grade, e.g. a 5w30 can shear down to a 5w20. As an example, according to Mobil 1's website, the HTHS rating of their 5w30 is 3.09 and the HTHS of the 10w30 is 3.14. So to some extent your dealership is correct, you get slightly better high temp protection with the 10w30. How much that is offset by increased wear due to high viscosity when cold is hard to say.
I'd say he knows a thing or two about oil and viscosities. I think the 10W30 would be ok for now, but next oil change switch back to the 5W30 for better oil start up protection.
Thread Starter
Racer
Joined: Nov 2005
Posts: 404
Likes: 0
From: KY
I really appreciate your responses. I figured everything would be cool. I guess I'm just a little paranoid sometimes. I also suppose I should have paid more attention to the manual when I was reading it.