PLEASE tell me my MPG will improve?!

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 :grinyes:

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.

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

Did that at 500 miles :grinyes:

Good deal my man.

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

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.

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

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.

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.

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

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).

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.

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?

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.

Your air filter wouldn't matter with break in.

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.

My 05 5.3 HO Z71 gets 16-17 around town, 21 highway. It's possible your gearing is wrong for the engine and truck size. Higher gearing does not always equal better mpg. Engines have an rpm range that they are most effective in,

I wanted to get a 5.3 w/ a 3.73, but I was sort of talked into this set up because it's supposed to get better MPG. 1 - 2 miles might not be much to some, but when you're putting as many miles as I do on a truck, it's a lot. So, I was really hoping the 16/21 would at least average at 17/18. I was really looking into a Titan, but it supposedly got much worse mileage. My Bro-n-law got one (CC as well) and he's getting 2 mpg on average better than me.

Were you talked in too this by the salesman? Sometimes they get trucks that don't move well, so they will tell you anything just to get rid of it. It does sound like you have a bad combination of engine size, truck size and gearing. My mpg improved with duel exhaust and a cold air intake.

Were you talked in too this by the salesman? Sometimes they get trucks that don't move well, so they will tell you anything just to get rid of it. It does sound like you have a bad combination of engine size, truck size and gearing. My mpg improved with duel exhaust and a cold air intake.

Listen to a salesman... nope. No, just by reading stats and talking to friends and... just by the sticker. I mean, I know sticker MPG isn't accurate, but even if it was as accurate as the 5.3 w/ 3.73, then it should be better in fuel than the 5.3

I mean, if they tested both trucks the same way, and the 4.8 tested lower, then they would have at least not shown it to do better... right?

When I first got my 2500HD with the 6.0/4.10's the first tank barely reached 200 miles on the trip and I about freaked out. It averaged about 8. As more time went by it got a little better. Now if I drive strictly highway at 65-70 it will get around 14-15. Town driving is only 11-12. I've had four different new 1500's with the 5.3's. Some with 3.73 and some with 4.10's. I found the 4.10's got a little better mileage overall with a mix of driving. The mileage will improve as time goes on but expect about 14 town 17 highway from what I've seen.

Cool, thanks for the advice. I'll keep y'all posted, it just sucks to drop this amount of $$ on a truck that I thought was going to get better MPG, when I would've gotten the bigger motor had I known different.

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.

Give it more time.. as you can see it is increasing.. I was not getting my best gas milage until after 20K.

Well, after posting on another board as well, I have decided to remove the K&N. Just so happened I needed to fill up the morning after the change, so I will update if my MPG improves.

Well, after posting on another board as well, I have decided to remove the K&N. Just so happened I needed to fill up the morning after the change, so I will update if my MPG improves.

Did you have just the filter or the whole air intake system?

Did you have just the filter or the whole air intake system?


Just the filter.

Just the filter.

You will see a bigger increase in power and mpd if you get in the whole system. the stock air system is designed to "quiet" the engine with the air baffles. those baffles restricts the airflow. see if you can get the K&N Gen II intake.

You will see a bigger increase in power and mpd if you get in the whole system. the stock air system is designed to "quiet" the engine with the air baffles. those baffles restricts the airflow. see if you can get the K&N Gen II intake.

My next bonus is in August, I might try that then. As well as new exhaust, and bed cover and.... :grinyes:

If you drive at least 26k miles per year, you can get an almost free VW TDI or Hybrid car. Well over $2000 savings in gas per year, which can come out near a monthly payment in gas savings. Plus you'd keep miles off your truck (except to drive for fun on weekends).

If you drive at least 26k miles per year, you can get an almost free VW TDI or Hybrid car. Well over $2000 savings in gas per year, which can come out near a monthly payment in gas savings. Plus you'd keep miles off your truck (except to drive for fun on weekends).


Yeah, another person where I work bought a Hyundai just while he's working, and drives the truck on the weekend. Not only do you save gas, but you can write about 95% of the mileage off (IRS doesn't like 100% :grinyes: )

trucks aren't built for fuel economy, they are made for working and that takes gas.........and lots of it.

trucks aren't built for fuel economy, they are made for working and that takes gas.........and lots of it.

But when your job puts you on Texas highways 50% of the day, you really want to be higher with the rest of the trucks. The best rated car probably wouldn't do so great against the worst rated truck in an accident. I even looked into a Canyon/Colorado/Frontier/Tacoma... their MPG wasn't much better than a full size. The only way to make a big jump is to go down and get in a car, which I really don't want to do, but may end up doing.

Trucks might fare better in accidents but cars avoid them better. My highway DD is a car and I could tell you some scary commuting stories about route 80 in NJ. I've avoided accidents which I dont think I could have in my 1500. Plus I get 45 real world mpg in my DD vehicle = 650 miles on 12 gallons of diesel. But then I dont have to use my truck much for work. Just a weekend toy. I would drive it more if I didnt drive so damn many miles.

trucks aren't built for fuel economy, they are made for working and that takes gas.........and lots of it.

What an ignorant statement! That does not mean that trucks can not get good gas milage.. besides why should I settle for crappy milage just because I like trucks. most Chevy v8's now get better gas milage then most other maker's v6's.

Trucks might fare better in accidents but cars avoid them better. My highway DD is a car and I could tell you some scary commuting stories about route 80 in NJ. I've avoided accidents which I dont think I could have in my 1500. Plus I get 45 real world mpg in my DD vehicle = 650 miles on 12 gallons of diesel. But then I dont have to use my truck much for work. Just a weekend toy. I would drive it more if I didnt drive so damn many miles.

I have avoided many accidents in my truck. if you know how to drive one.. then there is not a problem.

I have a 2004 silverado 4x4, extra cab with 5.3/ Average over the course of a year is about 17 mpg. At 75 i tend to average 18.5 at 65 I get about 20. Around town 15-16. I get a couple miles to the gallon less in the winter when it is cold. I have also heard the blended gas used in the winter (ethanol blend) can cause you to lose a couple miles to ghte gallon.

With my 04 v6 I average about the same as everyone else 17 to 19 mpg so I don't think the engines make much difference. The stickers rated mine at 15 city 18 hwy. The city is lower than the v8 rating but the hwy is higher, I guess the smaller engine has to work more to get the truck up to speed so it hurts in stop and go traffic. Can get as high as 22 if I'm being nice to it or on long trips and the worst ever was 16 on a day when I was stuckin traffic for 6 hours. Best advice but hardest to follow, be light on the petal.