Thanx for the info. I've only used 1 bottle and that was 2 tanks ago. I just got this van a month ago so I'm still getting used to A: my first sprinter and B:my first diesel. I plan on changing the fuel filter out in the next week or so. I bought the van with 88,000 miles on it and it's my daily driver so I've been trying to take good care of her. New air (k&n), cabin, oil filters, Mobil 1 X1 (****s expensive!), checked trans fluid, will flush coolant and already had to fix the roof top AC leak (seal around the top). I have noticed a slight squeal from the belt area so something might be going out. Anyway, thanx for all the info!