High Mileage

I have a 00 Silverado Z71 with a 4.8. Engine has 298,000 miles on it. It is starting tu use some. Thete are no visible leaks any where on the motor. Local mechanic suggested i switch from Amsoil to a conventional oil and going to a heavier weght. Currently using 5w30. He said the sythetic is probably passing the rings because it is thin.
Anyone have any thoughts on this?

How much is it "starting tu use"?

Over the course of a 5000 mile oil change it's using just over a quart.

Over the course of a 5000 mile oil change it's using just over a quart.

For an engine with almost 300k miles on it, that's really not that bad. You can try 10w-30, it might help, it might not. The only guaranteed way to eliminate oil consumption is to replace the valve seals and piston rings, which is a lot of work if you do it yourself or very expensive if you have it done professionally. If you do decide to do all that, since you'd have the engine torn apart anyway, you might as well just do a full rebuild.

You have obviously taken very good care of your truck. That kind of oil usage for that mileage is awesome. With that said I would not recommend changing oil brands. Amsoil is expensive, but it's done its job for close to 300k miles. As mentioned above, maybe a higher weight would help?

Good job!!

I have a 00 Silverado Z71 with a 4.8. Engine has 298,000 miles on it. It is starting tu use some. Thete are no visible leaks any where on the motor. Local mechanic suggested i switch from Amsoil to a conventional oil and going to a heavier weght. Currently using 5w30. He said the synthetic is probably passing the rings because it is thin.
Anyone have any thoughts on this?

if you have some oil loss during your 5K mile synthetic oil changes I would not be concerned. there are new GM trucks with 70K miles that have to add oil @2K miles. 300K miles I would continue the synthetic oil . also add when its low. I would also check the PCV hose system .. replace the PCV ... prior to the oil change like a few hundred miles add 5OZ of marvel mystery oil to the oil. this may help remove any carbon /sludge issues. I would also add the MMO to the fuel like 1 oz per 10 gallons of fuel this helps the upper rings to clean up and not stick. MMO is an oil not a damaging solvent I use it in all my engines big and small.. I did have a vehicle run 380K I saved a lot of $$$ wit that one..