New Caddy Owner/Gas Milage

[2002DTS]

I picked a 2002 DTS with 73000 miles a few weeks ago. I made a round trip from KC to Daton OH. I got about 20.5 mpg. This seems low as it was advertised at 27 mpg. The weather was great and I ran about 70 mph. Yesterday I changed the plugs. They looked ok but I thought what the hell. I was wondering if anyone had any ideas on anything I could check. Thanks for the help.

[Bruce Nunnally]

Congrats on the new-to-you Deville. Tell us more about colors and options and link a picture if you have one please.

You are on the right track. The first thing I recommend when you buy a used Cadillac is go over it thoroughly, change the oil, new air filter, check the air pressure in the tires, check the other fluids (transmission, brakes, coolant). The plugs should be good for 100K, but I'm okay with changing them at 73K.

A single trip mpg check is interesting. To be clear, and hopefully not being too obvious, be sure to reset the mpg to 0 at the beginning of the test and then read the average mpg at the end of the test. I know more than one person I talked to left the average mpg running, which included city and highway mpg, then was disappointed that the highway mpg was not as good as expected.

[Texas Jim]

I picked a 2002 DTS with 73000 miles a few weeks ago. I made a round trip from KC to Daton OH. I got about 20.5 mpg. This seems low as it was advertised at 27 mpg. The weather was great and I ran about 70 mph. Yesterday I changed the plugs. They looked ok but I thought what the hell. I was wondering if anyone had any ideas on anything I could check. Thanks for the help.

As Bruce said, check all your fluids, belts and tires.

Not for gas mileage, but for preventive maint.

Unless you bought it from someone you know, you don't know how it has been maintained.

I run 2 or 3 lbs more air pressure in the tires than the recommended pressure on the door sticker.

My door sticker says 30 all around.

I run 33/34 in the front and 32 in the rear.

The Cadillac DTS is geared differently than the regular DeVille.

It is geared LOWER for more performance, but that hurts the gas mileage a little bit.

I have a 2006 DTS Performance Model, that has a similar drivetrain to your 2002 DTS.

Meaning that it is geared the same way.

I usually get from 20 to 23 on the highway depending on how I am driving.

I can drive it REAL EASY and get 23 or 23.5 or I can drive the dickens out of it and still get 20.

I usually get around 21.5.

[Ranger]

20.5 is terribly low for highway mileage. You should be closer to 26. Check or a leaky FPR.

[BodybyFisher]

Retrieve your codes from the computer, you could have a problem that is hurting your fuel efficiency like an O2 sensor, or TCC problem, etc..

Post them here if you have any and we will help you with them.

You have an onboard computer, click how to at the top of this page go to READING DTC CODES, and do the procedure to get the codes

[JohnnyG]

The Cadillac DTS is geared differently than the regular DeVille.

It is geared LOWER for more performance, but that hurts the gas mileage a little bit.

I have a 2006 DTS Performance Model, that has a similar drivetrain to your 2002 DTS.

That's a good question. When did they change the "REAL" DTS, which I'll call the performace gearing version, to the "NEW" DTS? The NEW DTS in this case will be the taller geared, highway cruiser, like my 2008.

I'm thinking it was 2006, which offered both the Deville or DHS and the performance DTS, right?

My "new version" DTS fell a little short on fuel economy this last trip across Ohio, but still manged 27 mpg highway. When I say highway MPG, it is measured and the computer reset after reaching and maintaining 71 mph, which I found to produce optimum economy for this car. I filled up with Sunoco 87 in Pittsburgh, and usually run 89, so that might explain part of the difference. Or it could have been the heavy rainstorms that we had to drive through to get home. Usually it will return its PEAK MPG on this section of the trip, 28.5 mpg, measured over 100 miles.

[Texas Jim]

That's a good question. When did they change the "REAL" DTS, which I'll call the performace gearing version, to the "NEW" DTS? The NEW DTS in this case will be the taller geared, highway cruiser, like my 2008.

I'm thinking it was 2006, which offered both the Deville or DHS and the performance DTS, right?

2005 had the DeVille...DHS...and DTS.

2006 Had ONLY the DTS... in 4 different versions.

Lux l, Lux ll, Lux lll and Performance Sedan.

All the Lux models had the taller gears while the Performance Sedan (like mine) had the lower gears.

My mileage runs 21 to 23 at around 80/85 or so. Usually 21.5 to 22.