I used to use Valvoline Synpower (fully synthetic) 10w30, but then I did some research and decided to use Mobil 1 fully synthetic. My truck has always had fully synthetic 10w30, and for the biggest part of it's life, it has been Mobil 1. Now, I've been thinking about going down to the 0w20 Mobil 1. Would this hurt my truck? It has about 150,000 miles on it, and it's a 97 4.6. My oil always looks good when I drain it, and it performs well, I've never had any issues, so is this even worth changing for?

 

I'd never go to lower Viscosity oil than is recommended. It's possible that a lower viscosity could lead to quicker component wear and Engine damage.

On a High Mileage Engine the use of a Higher Viscosity can some times help restore some lost compression and Quiet noisy lifters.

But if your oil always has looked good and oil changes and you've no problems. I'd recommend staying with what you're using.

Doug

 

...if it ain't broke, don't fix it. I'd stay with the oil you have been using. I'm not sure if I would trust 0w20 ... sounds like lubricity problems, accelerated wear, and trouble.