Start with pulling out your O2 sensor and clean with oven cleaner. Put it back in and try another tank. Usually awful fuel mileage is a plugged air filter or the O2 sensor. Plugged cats is also an issue on these trucks as well, so good chance that's the prob.

During the Magnum era, the V10, 360, 318, and V6 are all within 1mpg of one another.

It was -5F yesterday and I got 14.8mpg out of my 360 Mag in a full-size quadcab, all highway, about 60mph. If it was town it would probably be 12mpg in this kind of cold.

Edit* Shoulda' got that white one.......