I just ordered some 5w-30 for an oil change in my 4.0L 2004 Jeep TJ. This is what the manual calls for when using the car in sub freezing temps, which it will be for most of the next few moths up here in Northern Arizona.

Anyway, I ordered a 5qt jug plus a single quart. I just realized that the single quart is 5w-20 not 5w-30. Will there be any disadvantages to running the single quart of 5w-20 in the car for the next few months, or is it worth the extra $10 to go buy a single quart of 5w-30 at the store?

I'm sure this is one of those "it doesn't really matter" situations, but I'd like to save the extra cash if I can!

  • 2
    Shouldn't be a problem at all. It will blend in with the other 5 quarts and won't hurt a thing.
    – CharlieRB
    Sep 27, 2016 at 20:20

1 Answer 1


The lower number is the viscosity at low temperatures - so 5 for both bottles. The upper number is the viscosity at running temperature; you could argue that if you use all six quarts, your upper viscosity is now 28.33. But that's going to be fine; in cold temperatures, it's the lower number that is most important.

Just keep topping off with 5w-30, and eventually it'll average out.

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