I recently bought a 93 Deville. Its in great shape. There is about 112,000 miles on it. My question is how can I increase my MPG. As of right now I get 9.3 MPG and as far as i an tell is correct and im not very heavy on the gas. Yesterday I put some gas (89 not 93) in it and got 70 milles and 7 gallons. When I drive 10 miles it drops a gallon. I have heard of some devilles getting 20 mpg. Does anyone else have this problem or is it just me. I understand it is a V-8/4.9L and requires alot of gas but this just seems crazy. Is there anything I can do to improve my MPG. Also I have a slight leak in my exhaust system im not sure if that matters.

 

Tune up will help. Clean/new air filter, new spark plugs/wires if necessary. Clean the fuel injectors. Properly inflate tires.

I get 12.5 MPG city driving on my 6000 lbs Escalade, 6 liter engine. It's not great, but at 6k lbs, it's not bad.

 

I just got my '99. It does get 21 MPG in general driving (city and highway).

But I think it might be a whole different engine and all that.

 

Your car is capable of 20+mpg if everything is in good working order and you use good driving habits.
Sounds like either a heavy lead foot or an issue that needs to be repaired.
Take your car to a qualified mechanic and explain the problem.
A 1 to 2 hr diag charge should be in order to find and maybe even correct your problem.
Many many things could cause this.
If you are a doityourself person and have some knowledge/experiance with electronic fuel injection we can help you through it.

 

No im not to heavy on the gas, so Ill have my mechanic look at it. In the Mean time my power steering line has a pressure leak, my power breaks dont work, my alternator is going, as well as the pipe infront of my cadilitic converter just snaped. This happend all in a week. Now I wish my only problem was getting 9.3 mpg.

 

Hello, hear you can see the Cadillac DeVille real fuel consumption in mpg or liters Cadillac DeVille fuel consumption, miles per gallon or litres/ km | Cars Fuel Consumption

All information how much fuel consumed your Cadillac DeVille is taken from owners manual. Also here you can see the real capacity of the tank.

 

I had a 1989 with the 4.5L TBI engine (I believe that's what the 1993 had), and I got 22mpg highway. The two biggest reasons for horrendous MPGs are a clogged air filter and clogged injectors. Replace the air filter, run a high-quality injector cleaner, and watch the MPGs soar!

TS