Okay, I have 5 qts 5w-20 and 5 qts 10w-40 Proline dino. I originally was going to use the -20 in my mom's Camry and the -40 in my car for the Auto-Rx rinse phase but now I'm wondering if I will get close to a 30 weight if I mixed the two 1:1. Will there be any negatives?