Dodge Dakota poor gas mileage


Old 11-15-10, 07:57 PM
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Dodge Dakota poor gas mileage


I have a 2003 Dodge Dakota SLT Quad cab 3.9L V6. The tank on this truck is 24 gallons. According to the website, it gets about 15 mpg city and 17 mpg hwy, with 16 combined. I mainly use the truck for driving to and from work. It is about 42 miles round trip from my house to work, which I drive the backroads. It seems that I am now having to fill up the truck about every 4 days. It doesn't make sense why a tank of gas will only last me 4 days. As I said, most of my driving is back roads, 35mph being the slowest speed and 55mph being the fastest.

I have Autolite Platinums in the truck and changed them out at about 60k miles. The truck now has about 110k miles on it. Not that it matters, but I do the oil changes at every interval in the service booklet.

Is this normal for me to be filling up the tank about every 4 days? I am open to suggestions.


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Old 11-16-10, 02:52 AM
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There can be countless reasons for poor gas mileage. A few of the main reasons are:

Bad driving habits (Having lead foot disease).

Transmission torque converter clutch failure, (transmission slipping). Does the transmission feel like it’s slipping. If yes, scan for codes, and post any codes.

Change transmission fluid and filter screen every 40.000 miles. Use only ATF+4 fluid. Add a cooler to the system, and never have system flushed.

Clogged fuel injectors. Clean using the “On the vehicle cleaning method”. Use only Wynns, OTC, or BG products. Don’t waste your money on any “Pour in the tank products”.

Low tire pressure. Maintain at “OE” specs.

Overdue oil changes. Use only Castrol GTX (organic) oil, and only “Purolator Pure One” oil filters. Change oil and filter every 3000 miles. Synthetic is “BS” and a waste of money.

Dirty air filter. Use only “Purolator Pure One” air filters on your truck.

Wrong Spark Plugs. For your truck you should be using NGK laser platinum part number PZFR6F-11.

Throttle body carbon buildup. Completely disassemble throttle body and clean each part separately in a parts washer. Reinstall using new gaskets.

Vacuum leaks. Rule out using engine vacuum pressure tester, and repair as necessary.

Carbon buildup on EGR valve or in EGR system. Clean valve and system with carburetor cleaner.

Overdue fuel filter change. Change every 50.000 miles
Cheap gas. Use a “Top Tier Fuel” and never let the tank level go down below half.

You need to get an accurate reading of the actual gas mileage. Fill the tank till the pump nozzle clicks off on its own. That way you’ll know exactly how much fuel you'll have to replace after driving for a hundred miles. Then take your right shoe off and go for a long level (no hills 50 mph ride). Don’t do any jackrabbit starts, and don’t kick down into passing gear. Do this for a hundred miles. Now go back to the same station and fill the tank till the nozzle kicks off on its own again. Now do your calculations to see just how close you come to the EPA ratings for highway.
Old 11-16-10, 09:31 AM
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One other item that could be at fault would be the oxygen sensor. I have a car that I would drive monthly over a 246 mile trip. The vehicle normally got 30-32 mpg on the trip. All of a sudden the mileage dropped off to 24-25 for two trips in a row.

I tested my oxygen sensor and determined the thing was shot. The vehicle had about 140K miles on it. I replaced the sensor with a new one and, bingo, the mileage returned to 30+ and has remained there since.
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