I have an 01, 6 speed manual, 2WD with 220,000 miles. It runs great and gets 20 mpg, highway.
Should I use an additive to clean the injectors? If so, which one? I don't want to screw anything else up, since it's running well.
Also, is there any other maintenance that I should do as far as "tuning up" a truck with this mileage? I've owned it since 77,000 miles and have done nothing to the engine. I can change oil and filters, but other than that I'm useless so nothing complicated
Thanks.

 

I believe cummins suggests adjusting the valves at 150k

 

Diesel is the best solvent out there. Try Power Service Diesel Clean or the like for a few tanks.

Adjust valves

Good fuel filter is your best insurance, Baldwin, Napa Gold, Fleetguard, etc.

 

Also check/replace air filter.

 

At that mileage I'd be checkin front and rear diff, t case, power steering, and trans fluids as well...