I have an E300D( 1997) that has 135000 miles on it. It misses sometimes and it seems to be dependent on where I gas up. If I use Chevron diesel it doesn't seem to miss but if I use some other diesel brand on the interstate, I get that problem. Are there differences in the type of fuel I use? Does the timing chain need to be changed in this type of vehicle? The maintenance book doesn't specify that this need to be changed. I do my own oil change and other maintenance religiously and it is in excellent shape otherwise. Thanks.