New truck nightmare

Kicker06 · 11-06-2009, 03:39 PM

- First off I appreciate all you do on this site. I have been searching it for a year or so while getting ready to by my new truck and it has helped out tremendously. As for my question:

- Purchased an '06 LBZ two weeks ago. Have changed the fuel filter, air filter, and oil. Will be changing the rest of the fluids within the next two weeks. I have cleaned the mass airflow sensor with cleaner. I have ran two tanks of fuel through the truck. Added BG244K to the 3rd tank and seeing improvement but nothing amazing. The fuel is not of the highest quality as it is in Fairbanks and I believe they have switched to a winter grade diesel. The first tank was 8 MPG the second was 7.4 MPG. I did hand calculations on both. I have had no issues with power. The truck appears to be running fine. I also have no codes or aftermarket products on the truck.

- So far I have driven city mileage (25 to 45 mph). I allow the truck to warm up in the morning for about 15 - 20 min prior to driving to work. While driving the dash states that I get 14 to 18 MPG. However, when the truck is sitting at a light or going below 35 MPH the MPG drop dramatically. I can literally sit at a stop light and watch the number drop. I understand that this is to be expected immediately after a fill up, however this still occurs when I have 100+ miles on the tank.

- My question is what could be causing MPG around the single digits? I understand that I will get my best mileage at highway speeds but I have to drive in town. Everyone else on this site claims thier MPG it is in the 18's if there is not a lift or other products on the truck. It is crazy to think that I can dump enough fuel during idle to go from 15 - 16 MPG to 9 in just a matter of 20 minutes. Please help as I love the truck but can't afford to drive getting the same mileage as a full size semi truck.

**IdahoRob** · 11-06-2009, 05:55 PM

At idle, you get 0 miles per gallon. Just some food for thought. You must idle a lot.

Average is 14-16 mpg around city for the LBZ's I know. That is without idling for long periods.

**ob_1jr** · 11-07-2009, 01:53 AM

to the forum!!

Where are you buying your fuel in fairbanks? If you buy it on base, that could be part of the problem. I usually buy mine at safeway on airport way. I know the LBZ does get worse mileage than my LB7, but i normally get about 14 mpg in the winter even with the long idle times.

How is the power on your truck? The only thing i can think of is that your cat could be clogged some.

**bigdaddydiesel** · 11-07-2009, 07:01 AM

WELCOME to the Neighborhood!!!

The brand of fluids DOES make a difference, but not THAT much of a difference. Also, although I would think that your truck would run funny because of it, you may want to get some MAF sensor cleaner and clean it for good measure. The CAT being clogged like OB1 said is also a thing to check as well. I personally would open that up if emission laws allow it in Alaska.

When you hand calculate, (Dumb Question here I know) but are you making sure to fill it all the way to the top of the filler neck to about the same spot each time right?

As for how the DIC operates, resetting it at each fill up will not give you your best average of how you are driving. Although not the most accurate, most of them are pretty close on the overall averages across many miles and tanks of fuel. If you reset it at every fill up you will see the numbers move like that all the time and it will never settle down to an average number that you get use to seeing.

But, if you are truly seeing those single digit mileages like that then something isn't quite right IMHO.

Since you are running city traffic only for the most part, try running in tow haul all the time. This will keep your low speed rpms up so that your turbo is not what is dragging you around. keeping them between 1500-1900 rpms is the sweet spot IMHO. If you are constantly using the turbo to get up to a speed of 25-35 and then having to stop again, I think this would make a noticeable difference in your mileage. But, it may not, IDK for sure...

kansas · 11-07-2009, 08:04 AM

I have found over the years that people have a tendacy to inflate their actual fuel mileage Truth of the matter is with alot of ideling and town driving combined with the winter blend fuel you are probably doing about average compared to everybody else I would check it based on highway driving only and make a decision from there. I have also found that winter blended fuel as well as where you get you fuel can make about a 3 mpg difference. Good luck and let us know what the mileage is on the highway via hand calculations.
Chuck

Kicker06 · 11-08-2009, 04:29 PM

Have cleaned the MAS with appropriate cleaner and still no change.

Will fill up tank and run to North Pole and back to see how the mileage is affected.

I do understand that long idle times do affect MPG. I will try to find an idle per gallon average and see what that number looks like.

The only thing that I can see is if the truck originally had a program placed on it that is still on the truck and eating my gas mileage. However I can't seem to find anything on the truck that would reinforce this idea. I really am at a loss trying to figure this one out.

Thanks for the help guys.

MakinPower · 11-08-2009, 05:02 PM

I agree that a lot of the MPG numbers you see on here might be a little over inflated. Your driving style also plays into this average. Are you heavy on the foot? My wife can drive my truck and get 1.5-2 MPG better than I do when we go on trips...I guess my foot is heavier! A heavy foot really drives the fuel economy down. It sounds like you really need to get some long term numbers to get a better feel for your fuel economy. After resetting the MPG indicator there will be HUGE swings in that average depending on what your doing. Idling will kill this number especially right after you reset it. Try going like a thousand miles before you reset it next and I bet (unless you do a lot of city driving) your numbers will be more like 12.5-13. Doing a hand calculation along the way will also help you get a feel for the accuracy of the MPG indicator

I would also suggest plugging the truck in at night if you're not already. Your truck will fire right up and be plenty warm in the morning when you go to start it. In the winter (UP of Michigan) I do this and I only idle my LBZ for only a minute or two before I take off...that is all that is needed if the truck is already warm, all you're doing is wasting fuel beyond that. Idling will get you 0 MPG everytime, and 15-20 minutes before each startup sounds like a long time of 0 MPG fuel economy. Sub 10 MPG doing this sounds about right.

What size tires are you running? I lost 2.5 MPG when I went to the 285's from the 265's. Tire size also makes a big difference in MPG.

Good luck, it sounds like your truck is running fine it might just be a matter of tweeking the way you're operating it. Let us know how things progress. And most of all welcome to the forum!

kansas · 11-08-2009, 05:09 PM

You can figure about 1 gallon per hour at a normal idle.

Quote:

Originally Posted by Kicker06

Have cleaned the MAS with appropriate cleaner and still no change.

Will fill up tank and run to North Pole and back to see how the mileage is affected.

I do understand that long idle times do affect MPG. I will try to find an idle per gallon average and see what that number looks like.

The only thing that I can see is if the truck originally had a program placed on it that is still on the truck and eating my gas mileage. However I can't seem to find anything on the truck that would reinforce this idea. I really am at a loss trying to figure this one out.

Thanks for the help guys.

**ob_1jr** · 11-09-2009, 04:27 AM

Quote:

Originally Posted by MakinPower

I agree that a lot of the MPG numbers you see on here might be a little over inflated. Your driving style also plays into this average. Are you heavy on the foot? My wife can drive my truck and get 1.5-2 MPG better than I do when we go on trips...I guess my foot is heavier! A heavy foot really drives the fuel economy down. It sounds like you really need to get some long term numbers to get a better feel for your fuel economy. After resetting the MPG indicator there will be HUGE swings in that average depending on what your doing. Idling will kill this number especially right after you reset it. Try going like a thousand miles before you reset it next and I bet (unless you do a lot of city driving) your numbers will be more like 12.5-13. Doing a hand calculation along the way will also help you get a feel for the accuracy of the MPG indicator

I would also suggest plugging the truck in at night if you're not already. Your truck will fire right up and be plenty warm in the morning when you go to start it. In the winter (UP of Michigan) I do this and I only idle my LBZ for only a minute or two before I take off...that is all that is needed if the truck is already warm, all you're doing is wasting fuel beyond that. Idling will get you 0 MPG everytime, and 15-20 minutes before each startup sounds like a long time of 0 MPG fuel economy. Sub 10 MPG doing this sounds about right.

What size tires are you running? I lost 2.5 MPG when I went to the 285's from the 265's. Tire size also makes a big difference in MPG.

Good luck, it sounds like your truck is running fine it might just be a matter of tweeking the way you're operating it. Let us know how things progress. And most of all welcome to the forum!

Did you correct for the bigger tires? Your odometer isnt correct when you put bigger tires on. I only lost about 2mpg when i went from stock 245s to 285s. I have drove my truck like a grandpa and i only gained maybe 1mpg. I get an honest 17-19 on the highway. driving to and from work and to fairbanks (i live in north pole)...i drive about 13 miles one way to work on the highway. This is summertime mileage. In the winter i average 13-14 mpg

**n0useforaname** · 11-09-2009, 06:04 AM

Here is the question everyone is missing.....

How far do you commute everyday? Are there a lot of lights?

Me personally...I commute 2 miles each way....that's it. And I idle every morning to warm it up, and if I do that...and ONLY that....I get about 7-8 MPG with Winter blend, etc..

In the summer and warmer months, I get about 11-13 MPG if I do that.

On a normal driving day, like a 30 minute trip I get about 15-16.5...

On a highway trip it's a guaranteed 17-20......the avg. is 19 for me though...and mine are ALL hand calculated.