Mixing Oil Viscosities


Old 03-15-02, 09:07 PM
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Mixing Oil Viscosities

What is the reasoning behind not mixing viscosities such as 10w30 with straight 30 oil if any?
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Old 03-15-02, 11:14 PM
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you can do it, but you are just changing the weight on the cold side a little if any. the 10 is the thickness of the oil when its cold and the 30 is when warm. You want a thinner vicosity at cold start up to go through the motor faster and thicken as warmed up. At least I think thats right...haha
Old 03-16-02, 08:27 AM
Join Date: Jan 2001
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Chevymudbogger is right you want the thinner oil when the engine is cold so it flows faster & thinkens up when the engine warms up to protect the moving parts. Thats why they make multi-viscosity oil.
Old 03-16-02, 11:09 AM
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Mixing oils

You can get away most of the time mixing oils of the same brand. But under no curumstances mix oils of different brands!

Hey you know the Castrol Syntech blend? Half Synthetic & half reg oil. We did that before Castrol did. Yep we took three qts Castrol 20 W 50 and put in 3 quarts Syntech. Chevy Small blocks can run 2 quart oil filters. While in the shop we had a lot of salesmen leave samples of their oil. Soo we mixed a lot of oils. like half a jar of Quaker State the the other half Wolfs Head & so forth. Some separated, some turned to snot. It all about the chemicals that company uses in their oil additives package.
Old 03-16-02, 03:42 PM
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Oils of the same weight/type can be mixed. I have done it in the past no problems.

You probably wouldn't have a problem even mixing weights, but it's not a good idea.

Oil's cheap enough by the case.

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