Re: 97 powerstroke long starts
A lot of people don't 'drive' their vehicles, they drive them relatively slowly and since most are automatics, the rpms will naturally stay low as per the computer programming unless they press the pedal to the floor.
Selecting a lower gear while on the highway in any engine for a set time, will help clean out excessive carbon. Consistent high rpms can help blow out carbon and clean the valves a bit. When you see a car suddenly accelerate to pass someone, or merge onto traffic and a plume of white smoke comes out of the exhaust, you can tell the vehicle doesn't see much action above the usual 2000-3000rpm. If an engine had it's way, it'd run at maximum rpm at all times. Vehicle speed in governed through use of throttle calibration, and gears. This is why hybrids often use CVT transmissions. A CVT when you mash the throttle will slowly go up to just under the engine's redline - and stay there, until you let off the throttle. It's just too bad that CVT's sap more HP than a conventional automatic does.
Anyway, a couple good, long trips may help you here. If you have the funds, go see a relative or friend out of state even and go through a tank of fuel and as mentioned, stay in the upper RPM range for a while. 5 minutes each way at say 2700-2800rpm should be plenty, as I think your redline is around 3000rpm with the 7.3L V8 TD.
Diesel's can take more abuse and stay at high rpms longer than gas engines as they are generally over built for their purpose. That purpose is hard work, not just driving around without hauling a 40' trailer. If you had 4.56 gears in your truck, even in overdrive you'd knowingly see 2500rpm at a consistent 70mph. If you are unsure which gears you have (knowingly either 3.73 or 4.10s), check the glovebox for a sticker, the ratio should be listed on that, or on a tag/plate on the axle (might be covered in road grime).
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!