Quote:
Originally Posted by Mystic ZR-1
Why is 10w40 so popular?
GM said 10w30.
Ya know, they're really smarter than we give
them credit for...  |
Good question, one I have wondered as well. The way I understand, GM started using Mobil 5W-30 on 1993 cars and beyond. When I bought my '91, I had no idea what was in it. After most here use 10W-40 Amsoil, I went same route. High Zinc, has all the GM ratings, etc.......Since then, I have noticed a smoother idle, and no " chain rattle" at all. That maybe due to the new AC Delco PF970C oil filter as well. But I hope it will run cooler some what in the summer with the 10W-40 as well. I maybe totally wrong with my conclusion, time will tell.
But also, I would think motor oils now are way better than in the early 90s. But this is an endless conversation, I think it boils down to preference, easy of availabilty, price as well.