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.
I have an '05 Hemi Ram. I can get 22mpg with the cruise on 75mph per the overhead console. When I try and figure it out by miles divided by gallons at the pumps sadly its not anywhere near that.
MDS didnt go in the Rams till 2006.
Several car magazines have dyno-tested RP and other oils. One of them mentioned that RP was the only oil which seemed to give additional horsepower every time they performed a test. And yes, they have been testing Amsoil and Havoline and others, as well. One of them also claimed that this is the cheapest way to get additional horsepower.
I keep very good gas millage records. I switched my Subaru from Dino 5w30 to Mobil 1 10w30 engine and both differentals to Mobil 1 gear oil. My gas millage did increase by 0.3 mpg +/-0.05. I will never recover the cost of one oil change in 100,000 miles by switching unless I use a very extended OCI.
Eddie, could some of your gains be reduced wear and a longer engine life? Kind'a hard to prove, one way or the other in one car. Your starter could have a longer life. Maybe you won't catch a cold this winter. Or, now that you are using a synthetic oil you could go down in viscosity and still protect the engine. I wonder if that would give another tenth or so mileage?
Eddie: I am always skeptical that a test with only one car vs a fleet will give reliable results. But its nice to see a person do a thorough check and report results to the degree that you did. I get weary of the quick reports of "I switched my engine oil (only) to synthetic and got 3 mpg more" .