Mpg issue with MT

Since I got my truck with one mile on the engine I have been getting 17-20 mph in town. I live in a small town with a 4 mile commute to work. Drive about 45 mph for three miles the rest are dirt roads. I haven't changed my driving habits at all and since I hit 1000 miles a week ago I have been consistently getting 13-14 mpg?? I even paid close attention today and drove home at a steady 45 mph in 4th gear at 2000 rpm. Never floored it I was even more conservative turned off the truck to see 13 mpg? Some days however when I run it up into higher rpms to get to speed and think I am going to tank the mpg I will randomly get 18 mpg? Could this be a cps issue? I will try to do the actual math on my next tank however it takes a few weeks to burn through a tank to get a consensus. Comp not reading correct mpg? Thanks for any thoughts!

 

I had the exact same issue. I got ridiculed and told that I didn't know how to drive or that I was an idiot.

I ended up changing my CPS. Honestly, I don't know if it was break-in or the CPS. My MPG improved greatly in the weeks following my CPS change.

If I was to cruise at 45mph at 5th or 6th gear, I would definitely 23mpg or higher.

I have been tracking my last 10-9 tanks, and my hand calcs don't seem to be much different than the On board computers.

 

The CPS really changed it that much? I've been wondering if it is true...

 

Try resetting the computer.

 

Disconnect battery?

 

Thanks. Will look into it. Have a build date of may 17'.

 

I've noticed I get better mileage shifting into 5 & 6 in-town. I was constantly topping out my in-city driving in 4th and since changing and using 5/6 a lot more liberally I've been getting much more efficiency out of the engine. Just have to be ready to downshift if you need some power.

 

Probably way off base but computed mileage is based the ability to measure either fuel flow or fuel consumed/remaining which might be questionable. I would use the OD A or B to track mileage over a full tank and do that for a few fill ups to average out the shut-off of the pump. Although break in isn't as much of a factor as it used to be I wouldn't personally discount it in every vehicle and would expect mileage to improve to some extent, possibly noticeable, possibly not. Tire size affects calculated mileage, smaller tires will give inaccurately high mileage(you're not going as far as the odometer measured) and larger tires will give inaccurately low mileage(distance traveled is more than odometer measred), depending of course on what tires the odometer was calibrated for on the truck. Even normal wear will change the OD and hence the circumference of the tires affecting accuracy though in my experience that's harder to notice since its so gradual. It's also conceivable that the place where you buy gas is guilty of using pumps with inaccurate fuel transfer guages.

 

Stop checking your mpg the wrong way. Do the math when you fill the tank at the pump. A 4 mile commute will not give a good indication of your mileage

 

Correct. Disconnect the negative terminal for about 15 mins.

 

Disconnect battery, hand calculate, report back. 16 to 20 for me and that's with armor and R TT. 13 or 14 is low.

 

Will report back. Never had a comp tell me my mileage until now. Used to always do the math. I had just been watching the comp for a few months and the whole time it was 17-20. It's just been after hitting 1000 miles that it had suddenly reported low. Hopefully it's just comp. as far as brake in. I would think the more miles in the beginning would transfer to better not worse mileage. Again I will check the math. I love the truck and am not trying to jump on the bitch wagon. I love this forum for what it's meant. Helping others diagnose the vehicles they love. Thanks.

 

A shot in the dark, Maybe check your rear diff for leaks? Recall for that said you'd notice a lack of power and possibly GPM reduction before failure?

 

Strange, if you check your MPG right after a fill up you'll probably get some crap numbers until you drive a couple miles. I just completed a 100 mile round trip driving 70mph and averaged 24.3 in my stock 6MT.

 

Up in Alaska, do you guys switch over to "winter blends?" If so, could this be the case?

When I used to live in Chicagoland area, the "winter blend" absolutely sucked for gas mileage. I don't recall when gas stations started switching over though.

 

I would think you should be in sixth at 45 mph on flat paved ground for best mpg.

 

Will def check the diff. Thanks

No winter blends here that I know of. Have been putting premium in every fill up.

24mpg sounds great. I was really happy getting 17-20 right out of the gate with very low mileage so I figured it would continue to get even better.

As far as 6th going 45 I guess I could get it there however where I am confused is that my driving habits have not changed, route has not changed, all flat driving while on commute and now significant decline. I obviously will now be checking the math and doing it manually to get a better grasp and record from there also reset comp as well to see if maybe the comp is miscalculated.