Dissapointed in MPG!

walleye guy · 07-07-2008, 07:51 PM

I realize that this topic has been beat to death, but I'm really sick and tired of my poor mpg. I have a ppe set on #3 and I am VERY anal about getting the best fuel economy and am extremely light on the throttle. My dic says I should be getting 21 mpg, but when I hand calculate, I got 16 mpg on my last fill. This was 90% hiway driving. 60 to 65 mph and not towing and I only got 16 mpg!!!!! I just cant believe it, just think if I didn't have the ppe, I would only be at 14 mpg!!!!!! I had the inj's replaced about 1,000 miles ago. New fuel filter and new air filter. New 265 tires. no other extras. 2003 crew lt. with 147k. auto tranny.

What do I need to do get my mpg up??????

chevelleguy · 07-07-2008, 07:58 PM

I would recommend an exhaust. Get rid of the cat. That alone boosted my millage to 19 on my 07.

**bowhunternkbay** · 07-07-2008, 08:12 PM

Yeah, if you haven't done anything to let her breathe, you're missin the boat. Add a CAI and good exhaust and you'll see a difference.

walleye guy · 07-07-2008, 08:30 PM

I don't have a cat on my truck. So what intake would you guys suggest? How about if I ppe mod, would that help? When I got the truck, it came with a 5" exhaust, which was way too loud! Thought I was driving in my old powerstroker..........lol

I have a stock 4" exhaust that I traded a guy for. I thought that the 4" would work? The local chevy garage told me that just the muffler alone was worth $800.00.

GmcLbz · 07-07-2008, 09:04 PM

Get yourself a good 4" exhaust w/muffler that should help it breathe without being too loud. S+B makes some nice intakes as does AFE. Are you running larger tires than stock?

**TYREBOYZ_DEMAXIN** · 07-07-2008, 09:28 PM

i see you had the injectors replaced,did you notice a difference in MPG change before and after the Injectors?

**Tow Master** · 07-08-2008, 01:41 AM

Wow adding a exhaust and intake will give you small gains compared to a programmer! What year Duramax do you have?

**n0useforaname** · 07-08-2008, 04:49 AM

^^^^I was wondering the same thing, if you can, fill out your signature so we know what mods and engine you have. If you are seeing 16MPG in HWY, a CAI is not going to raise that to the 19-20 you should be seeing. Because if he had his injectors replaced, I'm going to guess it's an LB7.

**TYREBOYZ_DEMAXIN** · 07-08-2008, 06:08 AM

its a 2003 Duramax so if i'm not mistaken that would make it a LB7 for sure..

walleye guy · 07-08-2008, 12:46 PM

Allright, got my profile updated. I did mention in my first post what the truck was, 2003 lb7 with 147 k . ppe standard the rest is stock. So why am I getting such poor mpg? I have been driving very light and am only getting 16 mpg. HELP PLEASE!