Quote:
Originally Posted by madmaxx
Mixing the oil as you describe is a very bad idea, The two oils do not congeal to form a 10W40, what happens is one half acts like a 10W30 and half acts like a 20W50. This came from both Mobil and Valvoline. I would stop this practice sooner than later. |
That's probably why Mobil & Valvoline sell both sell a 40 weight. Now I do not know the answers on this issue by any means, only what the tech folks at BP recommended. But I bet there's a petroleum chemist somewhere in the audience....