I have a 97 3500 dually and I run addditive in her all the time, Have found that it helps with mileage and H.P. but ya have ta make sure it has centane boast in it.[ She has 559000 Kms on her also]:thumbsup:try for yourself and see, thats the best way.It won't hurt just don't by cheap stuff. Later from Ontario Canada!!!!!arty018:I just purchased a 97 2500 and a mechanic told me that i had to run a additive since the diesel fuel now has a decrease in sulfur which is a lubricant for the diesel. If that is so what is a good additive to use?