I had a 1990 cadillac sedan deville. I loved the car and got about 22 miles per gallon. I recently bought a 1993 cadillac deville and am only getting 14 miles per gallon. I have had the injectors checked and air filter changed. Is there that much difference between the 4.5 and the 4.9 engine?
If you go to www.fueleconomy.gov you can see both vehicles should get about the same gas mileage. There could be many factors as to why this vehicle does not get as good gas mileage. It's possible that this engine was run harder and it does not run as efficiantly as your previous one.
You would probably have to check deeper than the injectors and air filter.
〉 Answered on Mar 25th, 2007 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines