I've got an 89 chevy blazer, 350 5.7 liter engine and I was wondering what weight oil I should use. I've changed it before but different circumstances leaves me forgetting what I put in it last every time. I had to replace the gas cap and I do not have an owners manual. I want to say brand new it should have used 5w-30 but I'm sure I should go up in weight. Or I could be completely wrong. What do you think.

 

5-30 should be fine even 10-30. ive been running 10-30 forever, just cause i bought a ton of cases of oil years ago and still going through them

 

5W-30 preferred but 10W-30 is OK too. If you don't live in a really cold climate I'd run the 10W-30. This is out of the Chilton Manual.

 

Depends on engines condition. but ive always used 5w30 in the winter,and 10w30 in the summer. if the motor has high miles and not a whole lot of oil pressure,i bump mine up to 20-50 in the summer. Been doing it for years,no issues.

 

Alright guys I appreciate the info. I'm gonna throw in some 10w-30.

 

I've been running 5w-30 in mine all year round for around 2 years with no problem.