33-34mpg freeway sounds normal. I get that going about 65mph.

If your "commute" and jobsite traveling is only 2-3 miles at a time, then high teens and low 20's sounds right. The first 3-5 min the ICE always runs, and I get really poor mileage. esp if I only drive for ~5min then stop.

Was your traveling pattern the same with the tanks before the last three?

I suspect even a sligtly lower temp is even worst for that really short commute and traveling you're doing now.

My wife commute is only ~8min long and she does that 4 times day (commute and pick up kids), and her average is ~22-24mpg.

 

If you had a 35 mph average, then started the car and let it idle for 10 minutes, you would very likely end up with a FE around 14 or 15, just from the idleing... You need to NOT sit around idleing, but jump in and drive the poor thing cold. You mileage will improve mightily.

To beat the whole warm-up thing, If you are going to be in town the whole day, put a bunch of cardboard in front of most of the radiator. The car will then warm up faster, and stay warmer. Note the zippered radiator covers on the fronts of the Peterbuilts that are mostly zipped up this time of year. If you have an outside outlet where you work, get a block heater, and put it on, oir have it installed. That will keep the engine at lest tepid between runs. That, in combination with some restriction of the radiator intake should help a bunch. When you are going to go on a long run on the highway, pull some or all of the cardboard out.

Mark, who used to live in Dubuque where it is really cold.

 

The "oil life" counter is correlated to oil changes at 10,000 mile intervals. If you are changing the oil at more frequent intervals, as many are, you can ignore that counter. Did you check to see that they did not overfill your engine with oil?

Sounds like something is causing your ICE to run for more of the around town driving than it was previously. Has the ambient air temp dropped that much that the ICE is running to keep the emissions system components above their minimum temperatures (as the system is designed to do) ? [ still sounds kind of excessive ]

 

Hi Duhawk

Now that I know more about your problem by the other posters and your responses, it sounds like your running a rich air/fuel ratio. There are many reasons to cause this to happen, but if the vehicle is now cleared of the problem, try resetting the Keep Alive Memory (KAM). The PCM may have adjusted a lean sensor reading by increasing fuel injector output. The long term fuel trim map may have been changed and stored in the KAM. If the service tech said all is fine now, then reset the KAM to the defalt settings to eliminate an incorrect rich air/fuel ratio memory. If any and all problems are clear now, you should start getting the mileage for your conditions and driving techniques.

To reset KAM, disconnect the 12V battery ground cable for a minimum of 5 minutes.
GaryG

 

Wait a minute, if your setting still for 10minutes warming up and only driving a few blocks at a time, your mileage is fine. Get moving ASAP and hope for the best.

GaryG

 

According to the manual, several minutes at a steady state in cruise will also re-set the KAM, by default.

MM

 

It may not be appropriate in this thread, but it would be good to know some "common" reasons that the KAM may have adjusted to the rich air/fuel ration. Perhaps the OP encountred one of those.

Also, would the KAM readjust itself after a while (without having to reset) assuming what caused it in the first place was fixed?

 

If I bump up to 65 mph my mpg drops to about 28. I would hope that a 4 cyl engine without an electric engine assist would get better than 14-15 mpg in town even if it was cold. I would have kept my Escalade ESV which consistantly got 16 mpg in the city. My last tank avg was 23.16 on Sunday. I have driven 18.7 mi since and I am already at the 3/4 tank mark. That usually didn't happen until about 70 mi and one other think it a full tank now reads 319 until empty when a month ago in was 395-402

 

Mark

Trying to reset a single KAM map at every RPM, Speed and Engine Load, one at a time, would take forever and waste alot of fuel. This is why the PCM/ED recomends a post repair reset for a retest of the vehicle. It is then necessary to drive the vehicle to allow the PCM to learn the values for optimum driveability and performance. Ref. page 2-24 of the '05 PCM/ED.

OCC, an example would be a clogged or bad fuel injector, water in the fuel, vacuum leak, bad MAF sensor or bad fuel. If the problem is fixed or clears up, I would reset my KAM right away rather than get a number of bad average MPG tanks.

GaryG

 

so I just take it in and tell them to reset the KAM?
I can't wait for HyMotion to release their battery to the public so we can just plug in and go on battery power around town all morning without the ICE even kicking in, or at least that is what they say will be available in early to mid '07.