Originally Posted by Ateam
Guys it is ridunkulous to say to "not do this" or not drive it hard and immediatly change it out! Lets take it a step further and say you used an oil with a "0" viscosity rating. 1 quart would barely dilute the mix to be a difference, let alone a 30 or 40 weight instead of a 60 for 8/9ths of the mixture. Do the math. Using one quart of 5/30 would give you a weight of 57 when averaging the mix. So if you think 10w60 is so much more protective than 10w57 than by all means get to the dealer asap!
You need to apply that averaging theory to the kinematic viscosity of the oil at operating temperature (cSt) , not the "weight" value, to get a true representation of how the overall picture will change.