I have been watching my odometer closely since buying the truck

I'm sitting at a 8th of a tank, 365 KM
Filled it right full

Something is going on here
No codes on the computer

I'm suspecting a superchip tune on the computer for high octane fuel because I found a receipt in the console for a Flashpaq Superchip purchase

Based on my math, 90L at 365 km is 4 km per litre
That's barely half the fuel rating

So I'm lost trying to figure this one out
Air filter is standard, it has a magnaflow performance exhaust
Shouldn't that help my mileage???
Anyone got ideas to solve this??

 

Is it shifting into OD when needed? Maybe not the issue, but is parking brake dragging? Does it smell rich when idling? Any smoke? Ho is oil consumption?

Finally someone whose mileage is worse than mine.

 

What kind of driving are you doing? I see you are from calgary so if this is the mileage your getting from crawling along on the Deerfoot at 5 o'clock on a friday i'd say you're doing pretty good lol
This winter i was consistantly getting 250km to a tank with the sled in the back, all in town driving and lots of idleling. Disgusting i know, but my plenum gasket is blown and these magnum motors simply aren't built/tuned to get good mileage by todays standards.

If the previous owner didnt take the superchips with him then forsure reflash your pcm with the 87 tune as a starting point.

 

This truck has barely seen rush hour in this city
It's just usual driving around.
OD engages quite nicely when it has to
And I'm babying this truck around. I don't stomp on it or have a heavy foot

I'm driving around on city streets. 60-70 km/hr
Odd time on deerfoot or Stoney Trail at 110 km/hr

I'm not seeing any smoke coming out the exhaust, not smelling a rich mixture

Only thing I can think of is replacing the MAP sensor
I'm thinking plenum as well but the exhaust ain't putting smoke out
I love my truck but with fuel at a 1.219 it's killing my wallet

Tempted to back driving my jeep wrangler till I figure this out
I was expecting at least 500 KM a tank. I realize the gears are 4.10 but I figure with 265/70/R17 tires. It should be balancing itself out. Maybe I'm mistaken.

 

The question about the PB sticking
I'm not noticing any excessive slow down. Seems to be normal watching the speed and rpms go down when I coast down

I mean honestly for 5.2L engine, this mileage is atrocious
5.9 I can understand this but damn man

 

I average 5km per liter which is about 14mpg, and 19.6L per 100km. Your not that bad right in the ball park for these trucks. My org window sticker states 21.1L per 100km city and 14.2L Hwy, to bad they don't get that. In my op a 5.2 will work harder to move the truck than a 5.9 just my op though.

Edit: Gas over here is at $1.28 per liter were I am, but in Van area it's over $1.47 per liter. Over $6 a gallon that's nuts and that's for regular.

 

Is there any fuel leaking-from the tank, fuel lines or injection system?

 

5 km per litre x 100 L is 500 km

I'm not even near 500 km yet
Barely 365 at 90L used. I don't know maybe my math is screwed
I'm figuring I can pull 400 putting the tank damn near dry
Just shocked it's this bad. You getting at least and extra km per litre that I'm getting
I'm still researching possible problems

The tank and under carriage is completely clean from what I saw
Not smelling any fuel under the truck by the tank or under it anywhere

Guessing my plenum gasket/pan is on top of the motor above the lifters
Think I can see it if I look down through the throttle body
Has to be a way to increase this number
I'm scared of what my highway mileage will be, yet alone towing
I haven't even gone on a road trip yet

 

As at as fuel prices go
I want to kick the oil executives in the twig and berries over this

With the barrel at the price it is, there's no excuse for these prices anywhere in Canada
I just reviewed my gas bill and noticed they jumped it $4 per KW and that's nuts to

Time for the govt to step in and regulate these prices
I can't see to many road trips for people this summer if we hit 1.40-1.50 in Canada
Still remember paying 60c a litre when I started driving, dad was telling me 30c for premium. I wish

 

Check your math and do your mpg figures over a couple of tanks.

Towing you will not like at all just kiss the mpg good bye. Towing my 5th wheel (5500lbs) if I remember right was about 6mpg at best average speed about 80-90kph.

I have 3.92 gears so not that far from you, if I had your truck I would up the tire size to a 285/75R16. I should add my motor only has about 65k on it so kind of new.

What's your tire psi at?

Edit: We run a campground and yes the gas price is keeping most at home we have like 10 reservations for the summer so far, we are not going to last long if this gas crap keeps up. People just can't afford it.