I have an early 03 with 316k and I've always used 15w-40 either rotella or motorcraft. I'm in GA and don't really haul a trailor much. I have 1 very small oil leak dropping from the passenger side on oil pan area thats been around for a long time. I drive 50/50 street and highway traveling. Is synthetic a better and cleaner oil that can go longer than 6k-7k and or change the weight as well? What about other manufacturers?

 

In mine i have used motorcraft oil and filters. Mine currently has 338k. Im not even closely responsible for the first 326k though. I wouldnt go more than 5k on the oil changes. Injectors and injector issues would be my main concern. The 6.0 uses oil for more than just lubrication and the oil is rapidly broken down due to the injection system

 

If you have 316,000 miles on an original engine I'd just continue what you have been using.

 

What he said

 

My last oil/filter change was Motorcraft Filter and MobileOne 5w40 Diesel. The motor is significantly quieter than Motorcraft 15w40, my cold starts are significantly improved also.

 

I think you answered your own question.

 

For me (in this order) either:

Scharffers 5w40
Mobil 1 5w40
Delo 5w40

I've been running Schaeffers 5w40 since may and it's some amazing stuff that has removed my stiction and cleaned my engine internals like no other. It's not cheap and costs as much as Mobil 1, but it is without question worth it to me.

 

Cool!

I just ordered 6 G of Schaeffer's for $190 shipped.

 

Awesome! Stick with it going forward and you'll be amazed at the results.