PLEASE tell me my MPG will improve?!

[KahneFan]

I have an 06' CC (pictured below). My truck has 2600 miles on it and I keep getting -15MPG. On a long haul of 200 miles highway, I got 17.5, but other than that, it's been 14.5. My salesman tells me there will be a big change after 3000 miles or so, someone PLEASE tell me this is true. Sticker is 16 - 21, I would be completely satisfied with the lowest end all the time (16), but 14.5 is sucking. My previous vehicle averaged 15, so it's not a killer, but it was definitely a strong point in buying a new truck for 16+.

BTW, I have the 4.8 with a 3.23, so there really isn't much of a chance I'm having too many jack rabbit starts

[jeverett]

After the engine breaks in, your mileage should increase some. I dunno how much, but you will see a difference. You might look into a K&N filter to increaes your mileage a slight bit more also.

[KahneFan]

Originally Posted by jeverett

You might look into a K&N filter to increaes your mileage a slight bit more also.

Did that at 500 miles

[jeverett]

Good deal my man.

You oughta be good for a couple more MPG after break in.

[tykrz]

I used to have a car that was supposed to get 35 mpg highway. I complained to the dealer several times because it only was getting 24mpg and was told the same thing. Anyway after about 15,000km, all of a sudden it got 35mpg on a consistent basis. I'd give your truck sometime as the PCM may be running the fuel induction richer for break-in purposes to keep internal engine temps down.

[ccski]

I have a 03 2WD 4.8L 3.42 gearing. Around town with approx 700# of winter weight in the back I get 16 almost 17. Only took 1 trip unloaded and avg 20mpg. Funny thing is I once had a club cab with a 305 , 5 spd manual that got great mileage. The delaers say these motors are much more powerful than the old hence the lower mileage. Either way at the price of gas it sucks

[silverado122775]

Just got to give it time.. the break in time is very important as the computer is learning your driving habbits. if you are gentle to the truck it will give you good gas milage after about 5K miles.

[RTR]

I've got an ' 06 5.3 HO with 3.42 gearing, automatic, 4x4. Last week at about 1000 mi. on the odo, I saw just under 21 mpg but with a tailwind. Typically it's been getting about 16.5/ 17, a little town, a little hwy, light footin' it.

[pnewcomb1]

IMHO it's important to run straight gasoline instead of ethanol too, especially during the during the break-in.

[gmtech79]

If you have 2600 miles the engine really doesn't have much of any break in left. The PCM is already doing what it needs to do, it will maintain 0% fuel trim (plus or minus 10%), which will make for a stochiometric fuel ratio. It will not run rich and then get leaner as time goes by, (government standards).

[KahneFan]

Here's what I've recorded...

348 - 16.27 (delaer filled up after 20 - 40 test miles)
591 - 14.57
938 - 14.72
1249 - 14.33
1552 - 16.86
1753 - 13.53
2093 - 14.58
2401 - 14.98
2684 - 14.80
3009 - 14.19
3237 - 14.84
3576 - 14.49
3872 - 15.77
4174 - 13.94
4533 - 16.12

TOTAL 4533 (/298.23) - 15.20

Per the sticker, my bottom MPG should be 16. So far my top has been 16.

[KahneFan]

One thing I do wonder about is the K&N. I put my K&N in at about 200 miles. Should I have waited for the normal break in period, then put my K&N in?

[gmtech79]

You also have to remember that the sticker is not really an accurate representation of fuel economy. Also your best economy is at 55 mph and above that your economy starts falling.

[gmtech79]

Your air filter wouldn't matter with break in.

[KahneFan]

Originally Posted by gmtech79

You also have to remember that the sticker is not really an accurate representation of fuel economy. Also your best economy is at 55 mph and above that your economy starts falling.

I drive much more highway than city. The city I do drive is very rarely in rush hours, so very little stop/go. I try my best not to stand on the gas when I don't need to. The only time I do is if I'm merging onto a highway, or into fast traffic. Other than that, I take it as easy as I can on takeoff's.