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I recently purchased a 2002 DTS. The vehicle only had 3900 miles and had been sitting for a while. Before selling the owner serviced the car. I am happy with everything except the fuel mileage. To say the least it is terrible. No where close to what was posted that this car should get. I feel I am a conservative driver and have never had trouble with any previous vehicle not getting what the manufacturer posted. I had the car serviced and was told all looked fine and there was nothing that could be done. Is this normal? I do good, pampering the vehicle all I can, to get around 10 MPG locally and maybe 15 to 16 on a longer trip. Any suggestions? I am about to the point of selling the vehicle. I might as well keep driving my large SUV. Actually I get just as good gas mileage, if not better.
 

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White Diamond '03 DHS (with DTS floor shift)
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That milage is not normal unless you are doing city driving with a lot of jackrabbit starts. Check for a leaky FPR first. Look in the Tech Tips section for how to do it. It's very easy and is a common cause for bad fuel milage.
 

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Thanks for the input. I'll have that checked out. If that is not my problem do you have any other suggestions?
 

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That mileage is very low, there's probably something that can be fixed and you'll be back up a few more miles. I don't see anything better than 16 MPG (combined city/highway) everyday.....which is probably "normal". Cost-wise, I feel like I'm driving a truck......
 

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White Diamond '03 DHS (with DTS floor shift)
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Challenge said:
Thanks for the input. I'll have that checked out. If that is not my problem do you have any other suggestions?
You are obviosly burning unregulated fuel. If it's not the FPR then I would look for a stuck open injector(s) but the FPR is more likely.
 

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If you have a 2000-2005 Deville or Deville DHS you have around a 2.60 gear ratio in the transmission. If you have a Deville DTS you have 3.70 gear ratio in the transmission. This is why the DTS will blow the doors off of the other two models. Not the 20 or so horsepower. I have a 2001 DTS and it gets 19 to 20 on the highway at 75 to 80 mph. My dad has a 2000 Deville and his gets 25 on the highway. With the low profile tires and gear ratio you are turning a lot of rpm's at highway speeds. I think you can put a taller tire on the car. I am going to try this in the coming weeks even before the tires are worn out. I think the EPA must have only tested the Deville and not the DTS for the fuel window sticker. A low gear is great in a sports car, but lets be honest this is big sedan. If I had it to do over I would buy the DHS just to get the better fuel economy. A 25% improvement with 40,000 miles per year @ $2.50 per gallon is a savings of $1000.00 per year. Our Suburban gets 15 to 16 on the highway. My (Leadfoot) wife gets 17.5 in her LS430 in town. I believe the DTS needs a different gear or a 5 speed auto as the Lexus has.

Mark
 

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White Diamond '03 DHS (with DTS floor shift)
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DHS & base Deville have a 3.11 final drive ratio. DTS has 3.71. HP difference is 275 vs 300
 
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