sil80er

This may be a stupid question but how bad would it be to mix two weights of oil like 10w30 and 5w30. my wife brought me home four quarts and two were 5w30 and two were 10w30 which is what i already use.

MABAGAL

the wieghts are still the same its still 30 wieght. the 5 and 10 you read is the temperature the oil is test when it becomes molasses so at 5 degrees that oil will turn molasses untill it warms up and so on for 10 degrees. so your fine.

MGBRaceman

I never do it. When temperatures get colder the two oils will seperate as you start the engine (the numbers 5 and 10 determined by how viscous the oil is at cold temperatures and how long it takes that oil to pass through an orifice) Why not take the time to exchange the oil and do what's right for your vehicle.

MAD_DOHC

You can mix them if you want, won't hurt. I used to run 3qts. 20w-50 and 2 qts. of 10w40 in my Bronco in the summer time and never hurt it. Just depends on what you want.

GaRn

Thats incorrect..

It won't hurt anything at all..

Fabrik8

Oils can't seperate under shear load like that, I don't know what you're thinking about but it's not oil.. Many oils are blended from different base stocks this way, it's the same thing. If you have a 50/50 mix of 5W and 10W, you should end up with 7.5W which won't hurt anything.


Think about it this way: If I mix corn syrup and light corn syrup together, and pump them through a strainer, will they seperate out?

dasboost

It doesn't matter if you mix weights, but I wouldn't mix brands. Different companies use different types of base oils, such as the Pennsylvania based oils (Pennzoil, Quaker State, etc.. using Paraffin based stocks). Here's a good site to check out:

http://www.bobistheoilguy.com

Go to the "Oil Forums" link on the first line. It is one of the best sites I have seen, and they have info on just about any automotive oil somewhere in there.