04.5 cummin HO 6spd horrible mileage?
 

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??

Haven't ever checked them to be honest.

If you hear loud ticking noise when you lift your hood then your valves need to be readjusted. Or if you can hear it beyond the hood. Valves can rob your Milage

I'll go have a listen.

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I can hear a very very slight tick over the usual diesel knock but it doesn't sound excessive

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I'll check them anyways. Does anyone know what the clearance should be?

Intake - .010
Exhaust - .020

They opened them up...I want to say its 0.010 and 0.026 now...I want to say this was put into play shortly after the dropped seat issues came into light, something about heat soaking?

I keep the .010 and .020 its kept my truck goin strong for 223K

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Also are you hand calculating or are you going by the MPG comp because if you dont reset the trip and mpg it generally doesnt come out rite. thats what I ve noticed in my mom 03 R/T Durango.

Air up the tires 70 frunt 60 rear. Is the tires stock?

They are those pressures and no they are 35s as I stated in the first post. I havent had time to check the valves yet but I've noticed that on average driving around town and making a few stops it only usually gets up to 150-160 degrees, and on longer trips it will heat up to 195-200. I'm wondering if this is hurting my mileage? It's around -10 here (celsius) currently so I'm considering covering half the rad, is this a good idea?

I have a radiator tarp on my truck I ran without it for a while when it was in the -10 -20 ferhnheight. It didnt hurt my gas milage when i was in the 150-160 degree's. But It will make for a warmer ride. I try to check you valves and have you ever changed air filter, and what rear diff gear you runnin?