If your mopar is you daily driver!

Let's face it -- you aren't driving an old Mopar for mileage. There really isn't enough difference between a small block and a slant's mileage to be worth a swap. Yes, you can do a lot of little tweaks to improve mileage, as folks have mentioned, but remember, basically, what you are doing is saving money on everything else: monthly car payments, insurance, registration fees (value-based in California), service (since you can work on your Mopar, but may not have the tools/expertise/time to deal with modern electronics). At least, I know I spend less on my car than people I know with late-model rides (or at least, I did before it went into the body shop -- now I might as well lease an Aston Martin <LOL>).