I have a 99 f150 4.6 with 165k. I have always used conventional motor oil. Can I swith to full synthetic?...nothing wrong with her...I could drive from here to NY and back and id feel pretty confident id make it. Just wondering about the oil.

 

Why change from what is working? I would never do it.

 

You probably could, but I don't know if I'd chance it with that many miles on it.

If it's not using any oil between changes *AND* you can verify that it's sludge-free, go for it. To verify if it's sludge-free, you would need to pull the valve covers.

 

Well I did have a po304 code so I pull off the throttle body and the tubes combing from the egr valve were completey blocked with carbon and soot, I cleaned it all up but wonder if the rest of the engine looks like the TB did?

 

Oh yeah it does use about a quart of oil between changes. It has ever since I bought it 10 years ago.

 

The two are not related. The TB has no oil sludge in it, t's from fuel.

 

Agreed....

 

i did the mistake of switching and now have major oil leaks and my engine only has 80k on it...

 

no its not

 

There are several suppliers of Walmarts synthetic oil. Look at the bottom of the bottle at your Walmart. If you see the initials WWP, it's made by Warren and is a Gp III decent oil. If those initials are not on the bottom of the bottle, it's highly likely it's made by Mobil/Exxon. Another decent Gp III oil. But neither are a premium oil and frankly, wear will be a little higher in analysis than a blend. Motorcraft and Pennzoil are producing the best wear metals....for now, anyway.