I have a friend who drives a Dodge Ram '05 with a Hemi, and he said when he put RP in it, he averaged over 22 mpg. He also said he slapped a bedcover on it (which I'm sure helped out a lot) but still, that's pretty d*mn good for a Hemi. I asked if he thought it might be the MDS, and he said he wasn't sure if his truck had it or not. In any case, he said his mpg went up when he put in the RP. He's pretty auto savvy, so I believe him.