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Farmer
Dodge Dakota
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11/22/2003
13:50:53
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 Subject: RE: Fuel Economy...
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I've got a 98 3.9 5spd xcab. 200KMs and high mileage pennzoil or castrol every 5000Km. I was pulling about 550Km out of 50-55 Litres. Then all of a sudden in August, she started to drop BIG TIME. Down to about 450Kms and now between 350-400Kms. I gave her a tune up about 2 weeks before all this happened. Just recently I replaced both O2 sens and put in a new OBD-II Cat. It's just getting worse. Any ideas??? I'm thinking about getting a fuel injector/system cleaning at a shop next.
Kev
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Richard
Dodge Dakota
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2/20/2004
17:56:31
| RE: Fuel Economy...
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Farmer
I am having the same problems.
Did you fix your problem and if so how?
Richard (not Dick)
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help
Dodge Dakota
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3/14/2004
17:58:12
| RE: Fuel Economy...
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I am going broke buying gas! Help !!!!!!!!!!!!!
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six pack
Dodge Dakota
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3/14/2004
19:37:44
| RE: Fuel Economy...
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99 3.9 shortbed sport 14+ in town od off short trips 23+ hiway steady cruise @ 75
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farmer
Dodge Dakota
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3/14/2004
23:18:36
| RE: Fuel Economy...
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Richard: I switched to Castrol Synthetic and saw an immediate improvement up to 450KMs per tank. I also butchered my box and pulled out the fuel pump. Tank was nice and clean, but I dumped a full bottle of carb cleaner in the fuel pump. That helped too; the guage is a little more accurate now as well. Should get better in the summer--less air,less fuel.
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BP
Dodge Dakota
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6/11/2004
12:28:35
| RE: Fuel Economy...
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at least oil prices are coming down and maybe gas prices next.
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LAD9DER
Dodge Dakota
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6/12/2004
00:01:13
| RE: Fuel Economy...
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What did you do when you "gave her a tune-up" Check your timing, did you replace the plug wires etc?? Any loss of performance other tha th eMPG decrease?
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another mark
Dodge Dakota
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6/12/2004
00:15:47
| RE: Fuel Economy...
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farmer - how do you know the gauge is a little more accurate?
My mileage new was 15.9 mixed, it's down to 12-13.5 now. New cat, new O2s and all new sensors on TB and new IAT, no change. I have no performance issues like stumbling or the like. Acceleration is excellent, mileage is crap. I don't get it either.
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Farmer
Dodge Dakota
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6/12/2004
19:34:15
|  RE: Fuel Economy...
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Before I removed the fuel pump, the low fuel light would come on at about 40-50L; after R&Ring the fuel pump, its closer to 60L. Weird thing- Dodge says there's 15 and 22 gallon tanks- The most I've ever been able to cram in there is 72L with the needle below the last line on the guage.
As for mileage, I'm getting about 7.5 Km/L which is lower than last summer; but higher than last fall/winter.
My tune-up consisted of the following
Synthetic oil & lube
Cap & Rotor
Plugs and Wires
K&N Air Filter
PCV Valve
I also just put on new summer rubber to replace my Ultra Grips and I'm getting a few more miles but not many.
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Bob Freerks
Dodge Dakota
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7/03/2005
09:46:45
| RE: Fuel Economy...
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I would like to reply only to the engine oil part of these posts. I am a PhD in chemistry and have worked formulating engine oils for many years with one of the only 4 additive companies in the world that formulate additive packages for engine oils.
All engine oils making API claims like SJ/CH-4 are highly developed products that have undergone over $1 Million in testing for each product to qualify for the performance claim. So any oil making these claims will meet engine manufacturers requirements for use in their engine.
Oil viscosity plays a small but measurable role in fuel economy. Synthetic oils are more often SAE 5W-30 viscosity grade or lower. This grade is very thin and pumps in the engine using less energy. Also viscous drag in the engine is less (piston to wall friction and windage are main impacts). That being said, the impact on fuel economy is relatively small. Standardized fuel economy tests show less than 5% and usually less than 1%. Using synthetic engine oil will not give a monetary payback. The fuel saved does not add up to the cost of the oil used.
I have been involved in NY Taxi Cab field tests comparing many types of oils from old cheap formulations to highly formulated synthetic oils. In short, we learned that changing oil frequently was far more important to engine life than using the best oil, even synthetics. The explanation is simple. Oil doesn't degrade, despite what advertising claims. The main source of deposits in engines is from unburned fuel that gets into the engine oil. To get this out of the oil, it must be changed. Also, synthetic and conventional oils all use the same additives. Amounts are dictated by standard engine tests. The additives wear out with use and time, requiring replacement. The Amsoil suggestion to change the filter means that the oil gets topped off with new additives frequently enough to make longer drains work in some cases. But if you have any fuel delivery problems (plugged air filter, bad O2 sensor, etc.) you will load the oil with unburned fuel which will cause deposits in the long run. Changing oil is the only way to remove the fuel dilution.
Modern FI engines have improved the situation over carbureted engines, and that has led to the recommended 7,500 mile drain interval. But for my money, I would change my oil every 3,000 miles and use any name brand oil that is on sale.
I have 100,000 miles on my 5.2L 98 4x4 and still get over 12,000 miles/quart based on how much oil has been used at the 3,000 mile change point. My Jeep 5.2L has 135,000 miles and also get over 12,000/quart. I use Chevron Delo 400 15W-40. The HD diesel additive package contains more dispersant and detergent additives than passenger car oils have. Look for the CH-4 claim or better (higher letter like CJ-4). It is available at Wal-Mart at a reasonable price in gallon jugs.
Yes, you can extend oil drain intervals, but unless you monitor the oil condition with tests, you really do not know how long you can go before you need to change oil. Recommendations are just that. They do not necessarily apply to you or your specific engine and driving condition. Considering that oil is cheap and you engine is not, make the best choice.
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N56629
Dodge Dakota
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7/03/2005
13:36:55
| RE: Fuel Economy...
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"Modern FI engines have improved the situation over carbureted engines, and that has led to the recommended 7,500 mile drain interval. But for my money, I would change my oil every 3,000 miles and use any name brand oil that is on sale."
So much for the Amsoil quackery. I have two vehicles with 200,000 miles on them, 1 Caravan and 1 Probe, both had fairly regular oil changes using whatever was on sale at WalMart and Fram filters. Yesterday I fired up the Caravan after it sat for the better part of two years, threw a 17' canoe on top and hauled it 40 miles. Don't believe in oil getting old either. I'm sure that I should have taken some precautions but at 200,000 the rest of it is falling apart and it has electrical problems. The engine will likely outlast the rest of the vehicle.
As for my '99 5.2, I get 16-17 mpg and it has 60k. I plan on taking care of it the same way as the others. Ditto on the '01 Stratus.
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