Hello, Allpar Forums member or visitor! If you were a member, you would not see this ad!
Register or log in at the top right of the page...
Discussion in 'Dakota, 1998-2013 Durango and Aspen' started by Peymack91, Oct 23, 2016.
...gets better fuel economy around town than on the interstate.
I had a '72 B-van that got 19 mpg in town and 14 on the highway. It was a slant-6 with 3.55 rear gears.
I attributed that to aerodynamics and gearing.
It's usually the gearing. Some that tow a lot have gone to 4.56 rear ends. Great for towing and the engine doesn't have to work as hard accelerating and in town, but out on the highway the 4.56 ratio hurts fuel mileage.
When I bought my '92 Dakota with the V6, it returned a steady 18.5 mpg on the interstates (meaning long-distance driving at steady freeway speeds, not the big-city stop-and-go rush-hour traffic). My brother found that the hose to the crankcase breather was cracked; after replacing it, the truck has generally returned 21-22 mpg on the interstates. City mileage has always been ~16 mpg. Maybe you have a vacuum leak, and repairing it will improve mileage and performance.
But if your truck already returns 21-22 freeway mpg, and city mileage is even better than that, don't change a thing.
If you go above 75 mph on the highway, with the 3.55 axle, your city mileage will be better because the Dakota is a brick pushing a wall of air. Numerically higher axle ratios will be even worse.
If you stay at 65 mph, highway mileage should be better (19+) and city about 16.
Keep in mind a 1991 Dakota is a TBI engine. It has a lot less power than the 1992 and up Magnum engines. That will affect gas mileage.
Not a big factor. My brother had an 88 Dakota standard cab 2WD V-6 5-speed, before the one I have now. He got 23-25 mpg highway.
I used to have a 92 V6 and it got 21-23 until the dang E10 came along. Killed mileage. Now have a 92 V8 and through the TN hills got 18.3 at 75-80 and sometimes 85.
Gas here in MO is terrible.
There's a new Murphy's Express fueling station near us. They advertise non-ethanol 87 octane for $2.399/gallon (E10 is $1.789), but as fast as they get the non-ethanol fuel in it sells out.
Try slowing down to 65 mph or so and I'd bet you'd pick up 1-2 mpg easily. The faster you go the more fuel you'll use. BTW - here in VA 80 mph or 20 over the posted limit will add a wreckless driving charge to the speeding ticket. Could mean jail time as well.
The speed limit is 80 mph on I-10 in west Texas (and probably on other Interstates west of Fort Worth). In east Texas, 75 mph is the limit on I-45 north and south of Buffalo, and even on US 59 south of Texarkana. Slowing down to 65 mph on those roads during busy times will make you a traffic hazard.
I'll agree that E10 degrades mileage, but my '92 Dakota still returns 21-22 mpg with it in calm, warm weather at ~ 70 mph. The only ethanol-free gas I've seen advertised on my north-south trips is in Linden, Texas, and I've yet to stop there, as my truck normally has half a tank or more when I drive through.
Don't forget I-20 from the border almost all the way into Dallas (at least to around where it splits with US-80 near Terrel) - that's 75 MPH also.
Which *ahem* the eastern part my 1988, 347,000+ mile Dakota quite often sees at 75MPH *grins*
Actually I see less mpg at 65 because going up hills the converter unlocks because to maintain speed ya gotta mash the motor. Driven both trucks to VA as my son used to live in Norfolk and Suffolk. In fact in Grayson, KY the fuel pump on the V6 quit as I exited the highway...within sight of the Chrysler/Ford dealer.
85 with 3.55 gears puts the engine almost at its torque peak.
Wow! Post something and don't check it for a week...
I knew someone would echo my sentiments. I don't drive on the interstate that often, so it's no big issue for me. And the numbers aren't that bad (around 19 city/17 highway). I think my timing is off, which kills performance, which kills economy. I have to get into the throttle to
get 'er moving.
If you have efi your ignition timing is set by the ecu. If you mean injector timing then that can affect things. Dont go in and start moving the distributor if you have mpfi. You will mess things up.
It is a TBI truck in this case. The timing is set by moving the distributor on the TBI engines. It's the Magnum (1992+) Dakota that timing can't be adjusted on.
Hence my stating MPFI.
Speaking of timing: how do I set it? I mean, I know how to set timing, but I've never used the magnetic style timing light. Can I use a conventional light? I found the hash marks on the crank pulley, but where are the corresponding marks?
There should be marks on the timing cover. The process may involve disconnecting the temp sensor. I don't have a service manual for your truck to verify the procedure though.
I'll check the service manual when I get home.
Cool. Pictures would help to find the marks if possible.