Do I have a problem???

[Shed]

I'm very frustrated with my truck and it's lack of mpg lately. With the rediculous diesel prices I have alter my driving style in an attempt to gain mpg. To no avail. I am getting 15.75 to 16.75 running 60mph on a 25 mile (one way) commute on the interstate. When I first bought the truck I had numbers around the 18-19 mpg mark. I drove to Kansas City over the weekend and ran 65 down the interstate with cruise on. Needless to say I got 16.1 mpg. No wind either. I cleaned the air filter, replaced fuel filter 4k ago, aired up tires, washed truck and not a drop of help. Got 17 mpg on the way back while adding 400lbs of cargo in the bed..... I'm confused. I also noticed that the truck has used some antifreeze in the past couple of months. The level dropped about 1/2" in the resevoir. Is this an indication of a problem? The exhaust has a very slight fuel smell but not all the time. Absolutley no fuel in the oil. No leaks in the driveway. Injectors done at 65k about 2 years ago (she now has 85k). I am frustrated and starting to think I made a mistake by buying this 01' cherry truck with low miles.... Any thoughts or encouragement will be appriciated. Sorry for the long rant....
Shed:(

[DieselMonk]

Most people forget that winter fuel has less energy than summer fuel. That's why you lost a couple of mpg's. I get less milage now on my truck and the car than I did 2 month's ago too.

[rob from bc canada]

Try these:

- You talked about "cleaning" your air filter - if it is an oiled air filter, you probably need to clean your MAF sensor - frequently. Many say stock dry type air filter is best.

- Using coolant slow and steady could be leak at water pump - hard to spot. If not, has it been chipped and run hard ????????

- Real world mileage on 05's like mine is 17-18 Hwy. I can get up near 19 under perfect conditions - but then, I haven't washed it lately :D I believe anything higher is in the mind of the beholder.

- 01's were actually known to get slightly higher mileage -

[Mark Rinker]

If your air filter is an oiled gauze type, I'd clean the MAF sensor, and try swapping back to the stock OEM piece and see what happens.

Also, do you run fuel additive? If not, try some in the next few tanks in case you have an injector hanging up.

Could you have an exhaust blockage?

[phill0072]

It's that time of the year, they are blending the fuel #1 and #2 together I see that you are in IA. and I know that most of the truck stops usually change over in sept, "just before the 1st frost". in all the states that get below 25 degrees. if you were in FL. I would be more concered. Every diesel truck or van I have owned gets lower mileage in the winter time. What really sucks is diesel goes up every winter and the mileage goes down for everyone that has to buy blended or straight #1 fuel.;);)

[Shed]

Thanks for the insight. The truck is not run hard and is not chipped, the only mods are the amsoil, intake, and exhaust. If the water pump is going are there any other tell tale signs? How difficult is a water pump to replace? Expensive?

I do understand the different diesel fuel blends a little, but this has been going on for about 6 months. Thats when I started to see little drops in the mpg. I hand calculate at the time of fill and do not use the mpg on the info center(don't have one anyway).

As for additives, I was running the amsoil additive in the summer, but ran out and failed to get more. On the trip home from K.C. I put in my winter additive (power service) which has a cetane boost, anti-gel, and lubrication quality. It seems as thought the mpg went through the roof!!! Figured it at 18mpg with some city driving and 2 warmup idles (bout 15 mins apiece).

Again thank you for your help and anymore comments are very much welcomed!!! Shed