I think 25 is optimistic in an Abody. Really depends on transmission/rear gearing/tire size etc... Challenger's have the variable valve timing (mdx?). As a matter of opinion 25mpg in a Challenger is tought to do, I drive a 5.7 Charger regularly and it doesn't get close to 25mpg.
I don't know if many guys have been able to use the MDX in older car applications.
