How will 5w-20 motor oil affect or what will it do to my 1998 gmc sierra z71?

Asked by Dec 12, 2015 at 10:01 PM about the 1998 GMC Sierra 1500

Question type: Maintenance & Repair

Didnt realize i had changed my oil with 5w-20
instead of what its suppose to have which is 5w-
30 untill i had already poured almost all of it in.

3 Answers


Possibly an increase in oil consumption. Top it off with 5W-30 if you need to.


That depends on if it is convential or synthetic oil and where you reside, if it is synthetic I doubt you will notice much difference, but convential a could give you a lower oil pressure reading when warmed up, so keep the RPM's down and avoid engines loads, just to be on the safe side you might consider adding a quart of Power Punch to the oil, that should make it last till the next scheduled oil change and you won't loose the oil already in there. HTH


It is winter and if it is cold where you are it should be ok- depending on the condition of your tired old engine-

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