Which oil do you need for a 91 V6 Jimmy?
This information can be found in your owner's manual. If you
don't have one, you can order one from a dealer. You may also find
one at a salvage yard. I have a 91 S-15 Jimmy 4x4...4.3L...and I
run 10W30 Valvoline in it year round. Depends on driving conditions
and weather. 5w30 is a good middle of the road oil. Make sure the
oil you use meets API standards. I just use 5w 30 year around.
Especially in the cold weather it circulates easier. Honestly your
owners manual should say 5w 30. However that is the manufacturers
suggested oil for when the car was made. What weight oil you use
especially for older cars should be based upon how many miles you
have on it. If it's a 91 I'd say you have over 100k on the clock.
Use 10w 30 year round. If you want in the summer you can use 10w 40
because oil tends to run thicker in the summer. If you notice any
oil leaks then up the weight to 10w 40 and 20w 50 in the summer or
use an oil additive such as Lucas.