a few months a ago my 92 deville was getting 24.8 MPG and over the last few months it has dropped to 21.6 MPG where it is now, i tried fuel injector cleaner and that did not help my mileage any. my driving style is the same and i have always put 93 octane gas in it? any suggestions on why and how could i get my mileage back to where it was? thanks

 

Air filter and tire pressure are two easy ones. Get a new filter and pump up the pressure. I keep mine at 40 psi, rocky ride but better mileage.

 

its got an almost new air filter and my tire psi is 35 on all four, i'll try that thanks

 

What about plugs, how old are they? wires?

 

not sure haven't changed them since i bought itjan 08

 

One year old, should be ok.

 

It may not hurt to check them and change if needed.

I just got my first Caddy, a '97 Deville D'elegance, at the end of September. Since I don't know the history, I've been going over things one by one. Like changing the oil even though it said there was 48% life left (did someone simply reset it without actually changing it?). On my first long highway trip with it it ran fine on the first leg but developed a strange "missing" on the return trip, which got worse over the following week (no SES). Most of my research indicated plugs and wires. So I bit the bullet and got them, and much to my surprise this engine is the easiest 8-cylinder I've ever changed plugs on! All they plugs looked about the same, minor deposits etc, but I found the #1 plug wire had a cut in it, down into the carbon. The "missing" is gone, runs a bit better than before.

I have not had my car that long, but after a trip to visit the grandkids a few weeks ago, the average MPG on the car (dash indicator) was 26.8. On paper it was 28 - even on a couple of tanks of 91 octane, which seems to be the best you can get in Kansas/Missouri area. It was the best 600+ mile one-way trip we have taken to date! This car replaced a '92 Olds 98 Touring Sedan with over 200K. Before developing severe electrical issues last year it would routinely achieve 30-32 with a supercharged 3800. I thought my T/S was comfortable (3 major back surgeries so far) and was a little upset when Oldsmobile went orphan, but I believe I found a suitable replacement.

Tom

 

i will check them the first chance i get, i know the car was well maintained,thankstom and katzmans caddy

 

would a climate change, and driving habits of that change be the reason? is this a one time mpg check, or is it a constant reading now?
rickyd

 

its gotten colder here over the past few weeks, my driving habits are the same, the digital average MPG use to go from 24.8 to 25 and now it says anywhere from 21.5 to 21.8, currently still at 21.6