This is the reason why I compare the weight of all the tires I'm looking at when I'm getting new ones. The factory Pirellis in 275/55/20 weighed 44#. I made sure all the tires I looked at were within a pound of two of that. I ended up with the Cooper A/T^3 which weigh 43# each. They do have a more aggressive tread pattern that did make a slight difference but I'd rather have that then get stuck.

 

Tire weight...height...tread pattern causing more rolling resistance all play a big part in a mileage decrease. Big reason I'm running P rated tires instead of the heavy LT's I ran when I was still working. I still need the all terrain tread since I'm out in the country. So far it look's like the tires may be guilty!!

 

Please don't think I'm giving you the idiot treatment, but, did you verify the corrected speedometer/odometer reading with a GPS or something equally reliable?

- Jack

 

Yes, It took me a while to figure out the tire revs per mile but finally nailed it at 650.. Speedometer is dead on with the GPS.

 

So next update:

I unplugged my battery for 10 minutes (1 beer's worth of time), and since then I've driven through 5 tanks.

See if you can tell where I did the reset, these are my last 10 tanks:

13.0mpg
13.4mpg
14.4mpg
14.0mpg
13.2mpg
15.9mpg
15.4mpg
16.6mpg
17.0mpg
17.1mpg

I tried to keep everything else unchanged, 8 of the 10 tanks were Casey's E-10 fuel. Driving was Iowa and Illinois. I keep my mileage in an app, so I'm not using the indicated mileage, but actual calculated mileage. I've verified my speedo against my GPS on my phone and my Garmin, so I'm good there.

I'll keep watching to see if it evolves... This was an unexpected result, I was just trying to eliminate it from the possible causes. I'm still confused on how it would affect my highway driving mileage.

 

Yeah - it's evident when that was done.

All that does is clear KAM/Adaptive. Clears out the LT & ST fuel trims and all of the various corrections fer sensor drift/skew/aging.

I'd expect that, barring an actual issue, over time yer mileage will return to where it was as Adaptive resumes it's duties.

 

I'll add a battery reset to my scheduled things to do every oil change. If it means a couple of mpg, it puts about $550 back in my pocket per year. Definitely worth my time...

 

No need to pull batt cables to reset /clear the PCM. Just pull the PCM power fuse. You won't lose any other presets/personalizations elswhere in the truck.

MGD

 

I get crappy mileage on Casey's E-10 too. Can you find pure gas anywhere? I KNOW I've seen it all over Iowa.

 

But, be careful about doing this or disconnecting the battery shortly before you have to take your vehicle in for an emissions check (if you live where you have to get one of those things). I know disconnecting the battery sets the P1000 (Drive Cycle) code and I'm sure pulling the fuse would do the same. If that code is present, you will not pass the emissions test (since your PCM is not considered "ready" for the test).

It can take a fairly lengthy period of driving to reset the P1000 code and the "procedure" to reset it sooner does not seem to be one that is easily accomplished.

- Jack

 

GLC - I've run Caseys the whole life of this truck, its never been an issue before, and I really haven't seen any better mileage on other fuels.

We don't have emissions checks in Iowa, woot woot!!!

 

Well, I know that 87 octane at Casey's USED to be pure gas - it's very possible it's recently been changed to E-10 now that the new Casey's stations I'm seeing have 3 grades of gas instead of just 2 grades like they used to have.

The stations that you use - 2 grades or 3? Price comparison between 87 and 89? If the 87 is pure gas it will be more expensive than 89.

 

I had a REALLY bad tank of gas today. But....

Cruise set at 78mph on I-35S from Minneapolis to Ames, IA.

Add a 17-20mph steady South headwind with some solid 25mph gusts.

Filled up with BP 87 octane, and got 10.9 from Twin Cities to Ames. Basically it was like I was driving 95-100mph the whole way home. Nothing but wind noise and gas sucking sounds...Almost 21 gallons in 225 miles. Truck pushing 5psi of steady boost on the level parts!

 

Was that BP E10 or pure gas?

 

E-10