10 W 40 Application

Patman

Staff member
Messages
21,989
Location
Oakville, Ontario
Are you sure GM specifies 5w30 for that engine? Even the new 3.8 engines out now all specify 10w30 actually. I wouldn't go with a 10w40 unless it's a full synthetic, as 10w40 conventional oils will thin out fast. Why is your mechanic saying you need 10w40 though? Is the engine burning oil? Just because an engine has higher mileage on it doesn't always mean it needs a thicker oil. If it's doing well so far on the 30wt oils, stick with it.
 
Messages
263
Location
San Diego, CA
My '98 Grand Prix GTP calls for either 5w-30 or 10w-30 depending on the temp. I believe the 10w-30 kicks in around 60F, but it seems to also show that 5w-30 can be run all year. When i took it in to the dealer last spring for a change with Mobil 1, they put in 5w-30. Maybe for the Olds put in 5w-30 in the winter and then 10w-30 in the summer? And i agree about keeping away from the 10w-40 unless you have a problem with 30wt. ferb!
 

MolaKule

Staff member
Messages
21,699
Location
Iowegia - USA
I would go with a good 10W30 blend, such as Schaeffer's #703, or Mobil 1 10W30 SuperSyn for both vehicles. I use both and am happy with the analysis result for both. In fact, I run Schaeffer's #703 in my '92 Suburban which has 257,000 miles on it. Consumption actually went down with Schaeffer's as compared to the Amsoil synthetic I was using.
 

Patman

Staff member
Thread starter
Messages
21,989
Location
Oakville, Ontario
quote:
Originally posted by Ferb: My '98 Grand Prix GTP calls for either 5w-30 or 10w-30 depending on the temp. I believe the 10w-30 kicks in around 60F, but it seems to also show that 5w-30 can be run all year.
Double check that again. I had a 97 Grand Prix GTP, and on the oil cap it even said 10w30 was preferred.
 
You can use 5W30 in the winter, but I'd go with 10W30 the rest of the year. Stay away from synthetics or blends at this point unless you're already using them. Pennzoil, Mobil Drive Clean, Chevron Supreme, and Havoline (Chevron/Texaco) are some of the better dino oils.
 
Messages
263
Location
San Diego, CA
I looked up the page in the manual for the oil specs. It does say that 10w-30 is preferred in my engine (3800 Series II Supercharged) but that if you live in cold weather a 5w-30 is an option. In the graphic the 10w-30 arrow goes down to 0F, whereas the top of the 5w-30 ends at 60F. And yes, i remember seeing the 10w-30 on the oil cap, thats why the dealer fill of 5w-30 in a Southern California springtime concerned me. I guess this brings up a decent point.. If an engine is running fine and not burning oil on a lower winter number, is there a reason to increase? ferb!
 
Messages
6
Location
Philadelphia,Pa. U.S.A
I have 1 1990 Olds with a V6- 3.8 as a 2nd vehicle. I have been using the 5W-30 as directed by GM in the manual. My mechanic says, I should be using 10W-30 but prefers 10W-40 because the car is aging. What would you recommend. I live in Pennsylvania, the winters can be quite cold.
 

Patman

Staff member
Thread starter
Messages
21,989
Location
Oakville, Ontario
Have you done oil analysis though? Sure the engine probably seems to run well on the 5w30 all year round, but you may have slightly higher wear metals with that 5w30. I'd stick with 10w30 personally. I think PA's weather is similar to Toronto and I'm gonna run 10w30 all year round.
 
Top