Being that the 2003 HO has a new common rail high pressure fuel system - what if any fuel additve should be used? I've read a lot of people with older trucks use marvel mystery oil. From what I can tell the main reason for an additve is increased lubricity for the pump and injection componets. Anyone have info that can apply to these new trucks?

 

Fuel additives in unit injector are OK, but only to a point. They are not necessary unless you run alot of poor quality fuel(IE: water, trash.) The tolerances in the unit injectors are so tight that the extra &quot;weight&quot; of the additives can cause problems such as sticking of the plunger in the barrell of the injector. I would suggest, if you are using a good to average quality fuel, to use one properly mixed tank full every 5-6 months or 20,000 miles. More often if towing(time) less often if just driving(20K.) Just like the #2 red diesel, the traces of this stuff can be seen during failure analysis if you have used too much. It's like overcharging you cooling system, just right makes it more efficient, but too much causes problems. <br>Brian<br>Volvo trucks North America Technical Support