Terrible Fuel Economy

[01Crewcab7.3]

Hey guys just looking for suggestions at this point. The last two tanks with my new DP Tuner I have gotten just barely over 300 miles to a tank. This is mixed driving with about 60/40 city/highway. I do not drive fast, and I always go the speed limit. I shift pretty low and never go over 2,000 RPM. I run the 80E in town and 60E on the freeway at 65 @ about 1900 RPM. I have 3.73 LSD with a 6 speed. Fuel filter has less than 2k on it, as far as I know no boost leaks. Where should I start looking or is this normal? I really thought that my mileage would go up with the tuner but at this point it is the same if not worse. Thanks for any help!

[ToMang07]

Well, first, how were you calculating mileage before, and what was it? Whats is it now?

I would start with checking for boost leaks, both the intercooler pipes/spider, and then the up-pipes.

[01Crewcab7.3]

Sorry forgot to mention I always hand calculate. The monitor thing has never worked as long as I have owned the truck. Before the tuner I would see around 14-15 with the same driving as now, and now i am around 10-12. As for the boost leaks I think I am ok because i still make good boost and my EGT's always seem low. I will check anyway. Anything else I should look for?

[ToMang07]

Originally Posted by 01Crewcab7.3

Sorry forgot to mention I always hand calculate. The monitor thing has never worked as long as I have owned the truck. Before the tuner I would see around 14-15 with the same driving as now, and now i am around 10-12. As for the boost leaks I think I am ok because i still make good boost and my EGT's always seem low. I will check anyway. Anything else I should look for?

Sure you don't just have a lead-foot problem?

Seriously tho, same size tires both ways?

What are you making for max boost?

Could be worth your time to check out the brakes and make sure nothing is dragging. Fuel filter clean/relatively new? Air filter?

[01Crewcab7.3]

I sure did the first two tanks after I got my tuner! 120 was just too much fun. These last few tanks though I have not touched 120 and I accelerate slow and keep the RPM's down. I was doing this to see what my best mileage could be and it goes down haha. I remember when i was researching DP tunes I read that there was an issue with the tuner and the gray CPS if I remember correctly. Has anyone heard of this before? Yup same size tires, same driving habits, literally the only thing that changed was adding the tuner which I heard nothing but good things about and was really looking forward to the increase in fuel economy. I will check the brakes this weekend. As for the boost question, when cruising at 65 @ 1900 or so I make a steady 4-5 pounds, and then when i get on it around 20, and accelerating on and on-ramp about 10-15 depending on shift points.

[01Crewcab7.3]

Fuel filter only has about 2k on it, and the air filter has about the same, the Napa 6637.

[ToMang07]

Do a couple WOT runs and check(post) your Boost/EGT's. WOT you should see around 30PSI.

[01Crewcab7.3]

Does it matter what tune I am in?

[ToMang07]

Originally Posted by 01Crewcab7.3

Does it matter what tune I am in?

I'm sure the economy tunes will get better mileage than running around on 120. I run on 80hp Daily Driver 95% of the time.... Been averaging over 18mpg unloaded.

I only go higher with a reason.

Like pissing off some little ricer in his civic.

[01Crewcab7.3]

Oh, yeah I know that I meant does it matter what tune I am in to check the boost?