Diesel fuel is usually 50+ cents a gallon more than gasoline--it was not until the past few months that I could buy diesel for almost the same cost as gas--diesel last week at my last fill up at the cheapest place locally was 2.15 a gallon--gas was 1.96...I bet once prices go back up,diesel will rise the most,and stay high the longest..
In my experience a NA 6.2 with highway gearing has about the same acceleration and torque of a 250 straight six..makes the most torque at low RPM's like a straight six...but if you hold it in the lowers gears and let it wind up a bit,instead of letting it upshift so soon with the stock govenor in the trans,they will keep up to normal speed ,unless of course your going uphill or towing..this kills off some mpg though..
"Chained Dog" is a bit much,but there has been times my pickup felt like it couldn't pull the foreskin off a mosquito...other times it feels as strong as a 454..its best performance is when your plowing with it,it likes to lumber along at low rpms and grunt..the fact it hasn't enough HP also helps the drive train live longer..