All I've heard, for what that is worth, is camshafts.
Here's the EPA fuel economy figures for the 420
Fuel Type
Premium Gasoline
MPG (city)
15
MPG (highway)
19
MPG (combined)
17
Here's what they say for the 300
Fuel Type
Premium Gasoline
MPG (city)
16
MPG (highway)
20
MPG (combined)
18
Jeff Zedic
Toronto
