is there any effect on the car if i mix .25qt of castrol 10w30 into 4 qts of mobil 1 synthetic 5w30? i just bought 4 qts of it and thought it would be gravy to add in the leftover 10w30 i have...would it make any differences negatively/positive?

 

matters not my friend...evil teken is correct as usual...

 

change your name to yoda you should...

 

5w30 in say 85 degree weather is going to burn that much faster than 10w30??