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bob brown
Dodge Dakota
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5/08/2008
13:12:24
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 Subject: gas milage
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i have a 2007 v6 and only get 14 mpg. friend has a hemi that gets more than i do. what gives?
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dakota49
Dodge Dakota
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5/08/2008
16:49:54
|  RE: gas milage
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bob, there are, or can be a lot of varibles as to why you aren't getting as good gas mileagew as your friends Hemi. One thing you could do is check for trouble codes, and if you find someone who can actually see what the engine sensors are doing while the truck is running would be a big help. Another thing is driving style, do you make a lot of short trips? A lot of stop and go? Mostly highway? All of those can make a big difference. Overall, I would say that 14 is pretty bad. My 88 gets around 18-22 around town/highway and a little better on highway only, and a little worst if city only, still city only I am getting right at18.
Good Luck
Dakota49
1988 3.9 4X4 5speed
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sport02
Dodge Dakota
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5/09/2008
00:01:26
| RE: gas milage
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wow, 2007 and only 14mpg. Is that on highway or city or a little bit of both? For a 2007 i doubt you have any codes but it's possible. Dakota49 is right, how do you drive? The dakota's are heavy trucks for a V6 and that is why sometimes the big V8's can get seemingly better gas mileage because they can pull the load easier but it's all about going light on the pedal. I have a 2002 V6 regular cab 2wd 5spd and i've learned real quick how to adjust my driving style. I only take rpm's up to 2000 and i shift to next gear. Don't down shift, you only rev the motor higher. get a cover for the bed. drive 65mph or less and leave a little earlier for work. stop passing everybody. don't haul anything in the bed. tire pressure at 35 lbs at least. no air conditioning. stop pulling out quickly. d these are just some things to consider and they do help. my 2002 gets about 21-22 highway and only mods are K&N drop in filter and flowmaster muffler. YOu should still be under warranty. Have the dealer check for codes, if nothing than seriously consider driving habbits, they do make a difference.
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daddio
Dodge Dakota
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5/09/2008
08:47:31
| RE: gas milage
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bob brown, what configuration truck do you have? CC, QC? 4x2, 4x4?
what config is your friends Hemi?
the latest gen of Daks is the heaviest yet.
yeah, 14 sounds low but we would need more info to determine if in fact it is low for your truck and driving habits.
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DakotaDog
Dodge Dakota
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5/10/2008
11:19:31
| RE: gas milage (16.3)
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Me too. Lousy gas mileage. I can't remember a time when I got better than 16.7 mpg even when it was new. Lately it's decreased to 16.3 mpg. 70% of my driving is cityish/heavy traffic. There has also always been a strong smell of raw gas coming out of the exhaust. Does anyone else have this?
Used to be tolerable, but now that gas prices are up, I'm wanting to figure out what the problem is. I'm going to try a few things - new plugs, air filter, etc. Might even try a HHO generator for the fun of it, but if things don't start to get a little better, I feel a (gag) Prius in my future.
==============================
2000 3.9L V6 2WD Quad Cab SLT
91,000 miles.
Solid Tonneau cover installed.
Tires: Yokohama AVID S/T P275/60R15 107T
Pretty much stock otherwise.
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dakota49
Dodge Dakota
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5/10/2008
20:59:22
| RE: gas milage
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You might want to check the O2 sensor(s) and the cat to see if its gone bad.
Good Luck
Dakota49
1988 3.9 4X4 5speed
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do the mods
Dodge Dakota
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5/10/2008
21:54:02
| RE: gas milage
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i did all of larrys mods and i get 21 in town and 23 highway
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DakotaDog
Dodge Dakota
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5/10/2008
23:11:34
| RE: gas milage
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"do the mods" - 21 in town is amazing. What were you getting before the mods?
I have been really disappointed with my 3.9L gas mileage since the day I bought the thing. I could have bought the next engine up (V8) and got the same piss poor gas mileage. Guess I didn't do my homework well enough... it won't happen again.
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daddio
Dodge Dakota
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5/11/2008
09:42:31
| RE: gas milage
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dakotadog, if you smell raw gas out of the tailpipe, you better check your pre-cat O2 sensor.
there are a lot of things that affect mileage. my practically stock '00 QC 3.9 5spd, 4x2 w/ 3.55:1 gears and 235/75/15 tires gets about 20 city and up to 24 hwy. V8 TB, CPS mod and underdrive crank pulley.
my truck is light compared to most. no p/w, p/l, 5 spd manual, manual seats, etc. all those power luxuries add weight which will not help mileage.
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DakotaDog
Dodge Dakota
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5/11/2008
14:23:31
|  RE: gas milage
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Thanks daddio. I went ahead and changed the upstream O2 sensor per your suggestion.
A small monkey wrench worked just fine for getting it out (no need to buy an expensive O2 sensor socket). The Bosch 13272 (supposedly OEM) O2 sensor has the wrong connector on it, so I ended up using a universal Bosch sensor spliced into the old connector. As I was splicing, I noticed a problem: on the old sensor, the insulation on the black (signal) wire and part of the gray wire had completely worn off, exposing the wire itself. This was about 1.5" from the connector. I don't know if it was rubbing against the frame, or the other wires, but it might well have been the problem.
Anyhow, it would behoove anyone suspecting an O2 sensor problem to inspect the O2 sensor wires to see if the insulation is worn through.
The gas smell is not so bad now. We'll have to see what that does to my gas mileage.
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dakota49
Dodge Dakota
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5/11/2008
17:51:08
| RE: gas milage
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DakotaDog, someone should have told you, the best O2 senors are the NKG the best. Mine is an 88 and with a Bosch my fuel mileage went down to about 15-16 MPG, I replaced it with an NKG and it came back up to 18 around town, but like I said mine is an 88, when I rebuilt the engine I had the heads milled as well as the block and my compression is up to 180 pounds on every clynder now. Plus I can play with my timing, I just can't increase the fuel, which I think if I could add just a tad bit more fuel I could get better power and better fuel mileage.
On highway I get about 22-23 @ 65 MPH.
City I get right around 18-20.
!988 Sport, small cab/bed 4X4 5Speed no power windo's locks ect. No A/C either.
Good Luck
Dakota49
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DakotaDog
Dodge Dakota
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5/11/2008
22:11:18
| RE: gas milage
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dakota49 - I have read back through the forums and I know that the NGKs are supposed to be better, but Bosch is what the parts store had in stock and the NGKs were about $30 more.
It's probably the same device wrapped up in different packaging, but maybe a larger variation in tolerance on Bosch. Could be you need a little more luck to get a good Bosch than for an NGK. :-)
According to the overhead average MPG computer in my truck, the mileage is running about 19 now, based on about 50 miles of mixed driving (had to take the wife out for mother's day - kids came too, so it was a heavy load). That's up from 16.3, so I'm initially satisfied -- but I think I need a week or so of driving to see what it really is going to be.
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pete
Dodge Dakota
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5/13/2008
11:52:05
| RE: gas milage
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I dont see how you can justify mileage based on 50 miles I thought when you check your mileage should write your current mileage down drive till your tank is close to empty refill up take note of # of gallons than mileage,subtract current mileage with previous mileage wrote down example 82500(current mileage)- 82350(previous mileage)= 150 miles driven took 16.00 gallons to refill full so 150/16.0= 9.375 mpg.Yea could estimate mileage after 50 mile drive but will not give you accurate gas mileage.And brand name 02 sensors BOSCH & NGK two different manufactures not a packaging difference by any mean that would be serious problem with two companies, some aftermarket suppliers do make OEM parts for the big three thats another story to talk about. When was the last time you check your thermostat or change it these trucks are know to operate up to temp or come close to temp than as you drive with your commute 50 miles your thermostat would drop in temp which could pull your PCM out of closed loop operation and run richer and suffer in mileage,your 02's like every seems to blame on for mileage yea if the 02 is lazy or fixed your 02 job is keep your air/fuel balance to 14.7 to 1 but anything not in tune with PCM will change your 02 readings and will make mileage suffer to. If truck has over 60,000 and never change them be a good idea to change them but if you dont know and bought the truck used, hook up a scan tool if you have one or reputable repair shop see how there switching than go from there. Sorry about the babble I get carried away to much........
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daddio
Dodge Dakota
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5/13/2008
13:32:46
| RE: gas milage
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pete, i did not tell him to "change" his O2 sensor. i told him to "check" it.
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pete
Dodge Dakota
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5/13/2008
23:41:19
| RE: gas milage
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I know you said check it daddio lot people do more parts changing than checking things out and waste mor money than whats needed.02 sensors are not cheap fix for gas mileage wonders either are these trucks if you want fuel mileage you bought the wrong kind of transportation and all these mods better plugs cap rotor wires MSD ignition etc.are not going help anymore than dress me up show again these trucks are not hotrods espicially a V-6. These trucks are only rated 15 city 20 highway +- a few mpg what else these if you get better thats great if you are suffering a drastic drop than I would say you need to start "checking" things out to find the cause to restore mileage. With gas prices raising more people are paying attention to gas mileage these days, in the day in say Larrys days and my peers they could to sh!ts about mileage they wanted horsepower and who cares about ozone poullants.Our generation wants mpg,horsepower, and ozone freindly transporation which we have alot to choose from again my babble is getting carried away......
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DakotaDog
Dodge Dakota
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5/14/2008
08:59:08
| RE: gas milage
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pete: I did qualify my mileage estimation based on only 50 miles, but I said I'd need a week or so to get a better reading (I'm not trying to BS anyone). Even based on tank measurements, gas mileage is subjective depending on a lot of variables (weather, traffic, driving habits, etc...) that change vs the period you choose to measure it in. So the vehicle trip computer is as good a way as any, maybe better. A lot of people in these forums quote their highway and city mileage and that's generally accepted. But I doubt they went out and drove a whole tank of gas on the highway, then a whole tank in the city to make that measurement. What exactly is "city" and "highway" depends on a lot of individual factors. There are no standardized cities or highways out there. Most people are probably looking at their trip computers or making a subjective estimate.
I have owned the truck since it was new, it has 91K miles on it. The O2 sensors have never been changed. The one I changed had a hole worn in the wiring. I changed my thermostat a year ago (it had a hole in it also). It's an old truck, I've had few problems with it, I don't mind just changing things that have a finite lifetime and are due to go bad anyhow, rather than evaluating whether they're still good enough and waiting another six months 'till they go bad and having to re-check them then before I change them. So I opt to just get it over with.
In my real job, I spend a lot of time evaluating and designing electronics. I happen to know that there is a limited number of manufacturers of sensors and integrated circuits out there - most of whom only design only one type of product for each application, or may only have minor variations. Most companies buy the same sensors and ICs from the same sources and repackage them - then market them based on brand name and perceived value. The only major performance differences are based on tolerance and the amount of testing per unit - you pay extra for that if you want it. I just take my chances.
As to my choice of vehicles, needs, people and circumstances change over time. If I could just snap my fingers and change vehicles any time I wanted to, I'd own a (gag) Prius right now, even though I love my truck and I would miss it. The reality is, you have to do the best you can with what you've got at any particular time. If you don't like the subject of this thread "gas mileage", then pick a different one.
Boy, we've spent a lot of time cross-examining, criticizing and nitpicking over every little detail of this that and the other thing and completely diverged from the original subject, haven't we...
I'm only interested in discussing how to fix my truck and maybe sharing some of the things I've learned along the way. I appreciate all the constructive suggestions people are giving me.
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pete
Dodge Dakota
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5/15/2008
11:20:13
| RE: gas milage
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Yea, most people dont drive till there tank is empty I would say when there engineering testing is done before the consumer (us) they drive till gas is totally gone and evualate mileage paremeters one for city & one for highway.Again didn't want to get off the subject either. Back to basics if you saying you have 91k miles on it Iam sure your 02's are switching alot slower than when it was newer and would reccomend changing them out for a maintenance item and have you swap out your water thermostat with the OEM temp rating they have tendency to cool off in temp after drive down the road regardless if you don't have any tempertature problems new thermostat would help keep a steady temp and keep your engine management in closed loop operation. I overlook this myself not thinking it would be a factor in mileage but it was one of my mileage benders I was having to which I had slow switching 02's and a thermostat would come close to operating temp then cool off after a drive seen on my scan tool while someone else in driving while I watching my scan tool even better if you have a laptop to record on good spreadsheet to compare all your sensor data a good mechanic that will spend the time and review all the data collected should be able to pinpoint the problem and save you some money and most all gas mileage...
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DakotaDog
Dodge Dakota
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5/15/2008
19:52:13
| RE: gas milage
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Ok pete. I appreciate your suggestions. I'm running about 17.6 mpg right now after about 200 miles as measured by my trip computer. That's a 1.3 mpg increase based on a new upstream O2 sensor (also put a clean air filter in) - I have never gotten that good of mpg even when the truck was new. I didn't change the downstream one 'cause I'm not sure what it does other than monitor the catalytic converter. Sensors are expensive. Anyone know what that one does?
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daddio
Dodge Dakota
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5/15/2008
20:09:23
| RE: gas milage
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as you said it monitors the catcon.
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Kowalski
GenIII
5/16/2008
08:01:29
| RE: gas milage
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DakotaDog, you are mistaken thinking the "trip computer is as good a way as any, maybe better" to figure milage. The method Pete suggests is more acurate. That's important, if you really want an inteligent discussion about milage - it needs to be figured inteligently.
You should also understand why the sensor monitors the catcon - it is to adjust the amount of fuel the injectors feed to the cylinders; regulated by the PCM. That's where the better milage comes from.
Lead, follow, or get out of the way
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Warren
Dodge Dakota
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5/16/2008
08:24:52
| RE: gas milage
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Kowalski, what military branch did you serve in? I only ask because of your signature at the end of your email...Lead, Follow, or Get Out of the Way.
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