hey guys, new here. got this truck a while back and lately ive been checking my mileage and it isnt very good, im getting around 10-11mpg empty, heres some info on my truck

2004.5 quad cab long box srw HO 6mt, has 300,000 kilometers on it.
just changed oil with chevron 15w40
4" AFE stainless exhaust
AFE Air Intake Horn
AFE stage 2 intake
Air Dog Lift pump system
Diablosport Trinity tuner
levelling kit, 35s @60psi front, 70psi rear
not sure what gear ratio
using howes additive

driving habits:
i drive fairly easy, shift below 2k rpm and im at 17-1800 rpm at hwy speed. i usually hit up to 10-15psi in every gear getting up to speed. tried the tuner set at performance, and extreme and noticed no difference in economy. when i just got 10mpg it was all hwy, and i had a small trailer with a quad on it, which shouldnt effect it much.

ps, this is hand calculated, the overhead says im getting 22mpg and i have corrected my distance for the bigger tires (+12%)

does anyone have any idea why it would get such horrible mileage? any questions feel free to ask if i havent covered it, thanks dudes!

 

How does it start first thing, any white smoke? Also, is your oil level on the rise?

 

Starts great. No problem and no oil is at full and hasn't changed since the oil change

 

Do you seem to get a lot of "rattle" driving down the highway, or when you come off a stop light/sign?

 

No rattling that I noticed at all

 

Injectors are still good then. What mods did you do when you noticed the decline in mileage?

 

I haven't done any mods to it. It had them all when I got it. I changed the oil and thts about it. I've only had it for a week or two

 

Try different settings on your Diablo and adjust the tire pressure to 50 front, 40 rear.

 

I've tried them all and haven't noticed an improvement. I went with 60/70 cause thats what the manual said. Surely higher pressure wouldn't lower mpg?

 

Ever done overhead.... Adjust your valves??