Hey all- quick question--I was running low on oil the other day.. didn/t have 5w-30, so I used 5w-40. Is this ok? Is it going to do any harm? Thanks

 

The only weights I would advise using are either 5W30 or 10W30 depending on the climate the vehicle is driven in. That said, the actual viscosity of a motor oil is going to vary based upon the manufacturer. I have seen oil analysis where a particular 0W30 was showing the viscosity of some 5W30's. It's not actually a cut and dried, written in stone type of thing.

 

you shouldn't mix oil weights. Vehicles can use a pretty good range of oil ranges, but it's bad if you mix one oil weight with another, IMO

 

Don't worry. In a pinch a qt. of 5w40 will not hurt a thing. It will mix and raise the viscosity only slightly. Although it is not recomended my guess is if you had all 5w40 in there it would not hurt a thing.

It is best to follow the owner's manual though. It probably says 5w30 on the filler cap.

 

It shouldn't, although as a regular oil change, I do not recommend this. If you go with a -w20 or a -w40, these oils are not the right viscosity for you motor. The weight is set by the manufacturer due to tolerances in the motor. Too thick can make it hard to flow in the motor, too thin will prevent the oil from doing it's job. Throwing in a quart of 5w40 to tie you over until you change your oil should be fine, however.

 

You are perfectly fine with the 5w40. Many people run 5w40 year round. You could even run 15w40 if you live in a warmer climate. I didnt see where you live. Dont sweat the 5w40, it is a very good oil and one qt will not harm your engine. Run your normal OCI and dont worry about it. 5 and 10w 30's are recommended because that viscosity range covers most any weather and drivings conditions adequately. That does not mean that it is the "best" under all conditions.

Also, when you are looking for higher viscosity ranges such as 15w40 and 5w40, just make sure it is API SM rated. If it is, use it with confidence. Some heavier oils are only diesel rated (CI only) and could harm your engine over long usage periods.