going to be doing an oil change this weekend, going to be using either mobile 1 or rp.. which weight should i go with?

 

i use the mobil 1 high mileage 10W-40 and no complaints. i wouldn't use anything lighter than 10W-30....SBC's don't like 5W-30 very much. i'd stick with mobil 1 unless you plan to go racing.

 

Use the same weight thats already in there. Ive heard 10w-30 gets slightly better fuel mileage,but i dont know if thats true or not.

 

Lighter weights do tend to reduce pumping loses a little. Many OEMs are going with 5W-20 these days.

 

i used to use 10W-30 but i haven't noticed any drop in fuel economy whatsoever. i think it has to do more with how you drive over how light of an oil you use. i only use the 10W-30 because it provides a little more protection to an engine with almost 130,000 miles and it tends to leak less.

 

my dad's 5.3 (1999, the bad year most blew up) uses full synthetic 5W-20 and it has 169,000 miles on it with no probs. It works great you don't have to change it as much.

Royal purple is over rated. use Valvoline or Mobil 1. They work great, also get a good filter 8 microns or smaller filtration and it will run for a long long time (family vibe has 180,000 miles on it runs great)