[NHRABill]

Hey Fjasper the curb weight of the DeVille is what is killing it. its probably 4,000lbs at least all that leather and steel and not much you can do without ruining the car. My wife has the SRX AWD 4.6 N* v8 and given the right circumstances can net mid to upper 20's on highway easily. problem is around town it sucks cause the weight is over 4500lbs.

I love love love the Caddy its a monster cruiser with the 5spd overdrive trans. Not sure what your parents has but if it is the same as my wifes 2004 keep it over 45mph but under 65 and you will net great mpg fro a vehicle its size and weight. As far as head gaskets goes 140,000 miles on my wifes car and no issues yet bought car second hand 2nd one she has had 1st was the v6 2wd but the v8 AWD is so much more fun and if you are practical driver can net same mileage.

Suggestion Pay attention to tires and turn the mileage gauge on inside the car so they can see how they are doing as they drive and what they average its a built in scan gauge Cadillac has had them a long time my 91' coupe deville had one way back when.