2001 Dodge Dakota Poor Gas Mileage

I have a 2001 Dodge Dakota 4x4, 3.9L V6. It has ~110,000 miles on it and, up until recently, was running strong. The past few months I’ve seen a drastic drop-off in gas mileage. I used to get 275-300 miles off of 16 gallons; recently that has dropped to 200 or fewer. I’ve had the oil changed or changed it myself every 3,000 to 6,000 miles, and changed the spark plugs less than a year ago. I had a fuel system cleaning done last year, too. It has a newer air filter, and I’ve added fuel injector cleaner a couple times. The tires are at the appropriate pressure, and still have a decent amount of tread.

It’s been idling a little high, sometimes consistently, sometimes intermittently. It often makes a sort of gurgling noise, like the sound of a kitchen sink draining or a diesel engine running. Every once in a while it emits a high pitched squeal/squeak when accelerating.

In a few month’s time, I’ll be driving around 2,700 miles with it, so I really need to get this problem taken care of. For an older vehicle and a pickup, I know I can’t expect stellar gas mileage, but I’d like to get it up to 17-19 mpg or so again. The major issue: I don’t have a mechanic that I trust. I’m used to going to the chain companies, and I always feel like they’re giving me the run-around because I’m pretty clueless when it comes to anything beyond oil, filters, and spark plugs, and I can never tell if they’re being honest with me. I know that gas mileage problems are tricky to begin with, but I really don’t want to take the truck in someplace and rack up hundreds of dollars worth of ‘repairs’ that don’t actually solve the problem.

I plan on getting a locking gas cap in case someone has been siphoning off my fuel, but I haven’t noticed a drastic drop overnight on the gas gauge and, given the age of the engine and the noises it’s making, I don’t doubt something mechanical is going on. I just don’t know where to start. Before I take it in to have it looked at, I’d like to have a better idea about what might be causing the problem. All the better if I can try a few things myself.

Anyone run into this problem before, or have any ideas what might be going on? I’d really appreciate any advice.

Try this simple trick. Park on a level parking lot. Turn off the engine and put the vehicle in neutral. Step completely out of the driver’s door and push the vehicle back and forth. If it doesn’t roll freely then you have a sticking brake problem. It could be the parking/emergency brake or pressure trapped in one or more of the rubber brake hoses that go to each wheel. A sticking brake(s) will kill your fuel economy.

"The major issue: I don't have a mechanic that I trust."

Check out the “mechanics files” link at the top of this page, and ask people you know for recommendations on local independent car repair shops. Gather several possibilities, and note which ones get mulitple recommendations. Then visit those to get a feel for the company, and gather some basic data such as their labor rate, how far in advance you need to schedule an appointment, etc. While you are there, you will get a better idea if this is a business you want to patronize as a regular customer. You want to know which business seems more qualified and skilled, as well as treating customers respectfully, being trustworthy, etc. Some shops will simply feel too casual, others too unfriendly, to suit you. If you know someone else who will be taking a car to their preferred shop sometime soon, you could just go along and be a fly on the wall gathering impressions.

Once you have identified a shop where you think you’d be satisfied to be a loyal customer, take your truck there so they can diagnosis your symptoms. Given that you seem to have taken care of your truck, chances are that your problem is something like a sensor beginning to fail, and not a terribly difficult or expensive repair. Or it may be just something like what missleman suggested which you can check yourself. You’re wise to solve this before your long trip.

You might try replacing the thermostat and gasket.

If the thermostat is stuck open the engine coolant doesn’t reach the proper operating temperature. When this happens the computer keeps the engine management system in open loop mode. In this mode the engine will use more fuel because the computer thinks the engine is still cold.


Thanks for your input, everyone. I will try the parking lot trick and have a look at the thermostat and gasket. Meanwhile, the search for a trustworthy mechanic continues!

+1 on the stuck thermostat.
Would cause the high idle too.
Beware of cheap aftermarket parts.
The squeak might be the serpentine belt. Is it over 5 years old?