Gas Mileage & 4X4 question

[hlenoble]

I have posted a few times regarding the poor gas mileage I am getting with my '03 XLT 4X4, V-6, towing package. This is despite installing a new air filter, and changing the transmission and differential fluids to full synthetic.

I was wondering if it's possible that the truck is ALWAYS in 4 wheel drive, whch would mean that there is a problem with the "4WD Auto" setting. So, my questions are: Would that be possible? If so, how would I check to see if that is indeed the problem?

Thanks in advance for the help.

- Hal

 

[JasonF]

Go on gravel, from a stop gun it. If your rears spin and then a half second later you feel a clunk as the fronts kick in, you can be pretty sure it was not stuck in 4wd. You would also notice it stuck in 4wd while taking sharp turns on pavement, you would feel the driveline binding up.

Jason

 

[jlinskey]

Hal,

From your previous post with MPG in the 16.5 - 17 range, I don't think that is that bad of a result. If you had a plain Jane V6 then you could expect to get over 20 + MPG on the highway. Add the 4x4 system then subject 1 or 2 mpg, and then add the tow package and subtract another 1-2 mpg; you will end up with a vechile in the 17 - 18 mpg range.

Depending on the number of miles on the truck, if you have over 36K then you may want to run some injector cleaner through it just prior to your next oil change. From experience, I recommend using the Techron injector cleaner at least once a year or ever 15K miles. It seems to really make a difference in my cars, and I have been using it for 3~4 years now.

Also make sure that your tires are properly inflated, because that would have a significant impact on mpg. Does your truck have the stock size tires on it? Any increase in the tire size will hurt the mpg. More over have you replaced the factory tires with another brand/type? A good highway/road type tire will help you obtain a higher mpg. When it comes to tires it is a trade off between what people may think is cool and the ill effects to their mpg. I went from stock to 31" tires on a jeep once before, and I lost about 4 mpgs due to the increase tire size.

If you can live without your roof rack, removing the center bars would also reduce wind resistance.

 

[Oldwolf]

Well you see, I have the same truck he does except mine is 2002. I get 17 or so in town and on the higway between 22-24 speed depending. I have 98,000 miles on mine too.

 

[jlinskey]

Well I have a '03 XLT 4X4 V-6 w/o the optional tow package, and I am getting about the same mpg results as OldWolfe. However then again I drive like an old man (for a 30 year old), properly maintain the vehicle, and check the tire pressure often.

Other factors that will effect his MPG:
- Driving habits - This plays a significant part. My wife's driving style causes my truck to get significant lower mpg.
- Tire Size
- Tire Type (there is a difference between highway tires and mud tires)
- Tire pressure
- Engine related issue - have you replaced your oxygen sensor after 60K miles?????

 

[hlenoble]

I appreciate everyone's help and suggestions, and I want to give you all some more information:

I bought the truck with 27K miles, and now have 34K. I changed the air filter and went to synthetic motor oil, transmission fluid, and differential fluid about 5K miles ago. I added a can of Techron at that oil change as well. The tires were brand new when I bought the truck. They are stock sized Kelly Safari, and are not a very aggressive (off road) tread, and are inflated to 34 PSI as per the sidewall recommendations. I do NOT accelerate briskly from a stop, but I do use cruise control on the hwy and typically drive at 74 MPH (per my GPS, the speedo reads 71).

I am not expecting to get 25 MPG, but close to 20 on the hwy would be appreciated, and be much better than my typical 16 - 17.5. Around town I would hope to get etter than my normal 13 - 14. So again, any and all ideas are welcomed and appreciated.

- Hal

 

[FordLover]

keep in mind the tow package replaces the 3.55 gears with 3.73's May not sound like much, but it is. also driving at 75 makes it drop, I rarely get better than 18 driving at 75, drop it to 60mph and the mpg goes to 19-20.

 

[Bottomlesspit]

Hal,
One quick thing that caught my eye with your above information is that 74 mph that you drive. That speed will really take a hit on your mpg compared to even 65-70. The loss in mpg is exponential above 55...not linear at all. Each additional mph over 55 starts giving you a real hit to amount of gas used, and each mph increase horribly hurts you. Anybody remember some of the actual numbers? I remember reading some studies and I was totally amazed at what just 1 mph increase could do. It is all based on parasitic drag and I know for fact that it is not a 1:1 tradeoff. We work with this in my aerodynamics class all the time and teach this concept to our military flight students using perfomance graphs to calculate actual numbers for our military aircraft.
Anyway, I think this area is definitely something that bears closer scrutiny for your mpg woes.
Good luck and hope you find what your are searching for. IMO it's gonna' require a reduced speed.
Ken