I am running a 2001 jeep 4.0, and was wondering if there is any benefit to adding some straight 30 to another oil. I have read that a straight weight will hold up to shear better than, say a 10w acting as a 30 because is is a real 30 weight. My jeep call for 6 quarts of 10w30, would there be a benefit of mixing 4 quarts 5w30 and 2 quarts sae30 to get a oil similar to 10w30 yet will hold up to shear better? Is this unnecessary with todays synthetics? Thanks