Its late and I need to put a quart of oil in my car before it gets dynoed tomorrow and the only place I can go is Wal-mart. Right now I have Royal Purple 5W-20 in my car and all they have here is royal purple 5w-30 or a different brand of 5w-20 such as mobil 1. What should I go with? Its not going to really effect the engine putting a quart of 5w-30 in with 5 quarts of 5w-20, will it?

 

Id stick with the 5W-20 in a different brand. I don't like to mix visconsities.

 

mix oils ok...mix dif weights... not ok

 

for sure?

 

My current oil is one quart mixed. I have 5q of 10w-30 and 1q of 5w-30 (same brand and full synthetic). I've had the oil for a little over 5K miles in there. No problems at all. It's not like this is a top fuel drag car.

 

Mixing different weight oil is a bad thing. Mixing different brands is very common, even mixing different types like say you put 5qts of synthetic and one quart of non synthetic is ok. Different weights don't mix well and you get build up.

Also, yes your car is not a top fuel dragster, they tear those down after every pass, you expect your car to last a while and any type of oil build up can keep good clean oil from getting where it needs to go.

 

what they said! ^^^^^^^^^^

 

Well all I know is it's perfectly fine and one quart with a very small different weight is not going to hurt anything.

People get so paranoid over oil for no good reason.

 

Well it all worked out I put a quart of mobil 1 5w-20 in it and it runs fine. Thanks for the help guys

 

Too late. I was going to say that I'd rather mix the 2 Royal Purples than mix M1 with the Royal Purple. The reason being is that both weights of the RP most likely have very similar additive packages whereas the packages in the M1 may not mix well or may even detract from both oils properties. Regardless, you should be fine with the M1 for awhile. I'd just change the oil at the earliest convenience.