engineermike

Forgive me if you've posted this already, but did you pull the plugs on the 2 trucks and check gap?

Centexguy

Hauled my four wheeler in the bed at an average speed of 76mph and got 17.1mpg. Not bad considering it weighs 700lbs. My best to date is 19.7mpg. I'm quite happy with it.

ajrothm

My life to date mpg is only 14.5. I average around 14 mpg in the city and have gotten 15.5 mpg on hwy trips. Best ever hwy trip was 15.8 mpg. These are all hand calculated averages. The lie o meter is usually 1 mpg happy on average.

Also this is with a 2" front level and 33x12.5x20" tires. I only had it a week before wheels/tires went on it so I never got a true average with stock 18s, I know the lie o meter was showing 16 mpg for that week though.

I now have the LMS tuner and my speedo is recalibrated to match my GPS exactly. I still only see 14.5 mpg on average around the Houston freeways and stop lights. I just learn to accept it.

Heishman

@ ajrothm- check PM.

engineermike

At 14 mpg and 336 rwhp with a LMS 93 tune, yours seems to be down on power and mileage. Have you checked your plug gaps?

MadocHandyman

Haha, I think we are becoming a pair of scratched records! "check your plug gaps!"
:-)
Do you think that this could also be the reason some guys can easily hit mid 14's in the 1/4 but others are having trouble getting out of the 15's?

ajrothm

No I haven't checked the plug gaps. But it dynoed 309rwhp hot right off the street with the stock tune which I thought was pretty strong. 45 mins later I flashed the LMS 93 tune in and it made 336. Truck never even came off the Dyno. I think it cooled down TOO much and that hurt the numbers some.

As for the mpg, I leveled the truck and put the 33.5"s on it the 2nd week I had it so I just assumed that's where the mpg is missing. I have 17k miles now and it's been getting the same mpg since 600 miles.

goodburbon

My truck got better than 18.5 at an average speed of 79 with my motorcycle in the back and a few hundred pounds of luggage in the cab. While my wife's got 16.5 or less unloaded on the same trip.

This isn't about you or your great or horrible mileage. This is about finding out why there is a difference. If most of the people who've commented in this thread had read the first post they might have noticed that their input was not welcome unless they were performing the same types of tests, so we can compare apples to apples to apples to apples.

goodburbon

No I have not, I'll have a look this afternoon.

pasprobe

I'm also really upset with the bad MPG of my truck compare to my friend MPG, I got 15 at 65MPH and he got 21 at 65MPH following me, so I take his truck for a week and he take my, I did 19MPG to go at work compare to my truck that generally do less than 14. He did 14 instead of 18. So there is something different on both truck. Both truck are nearly the same: 2012 fx4 screws 3.73 black (if the color do something with mpg), same tire, same tire pressure, same 5stars tune, I do have a bed cover and he doesn't, so we have both exact same truck with completely different MPG.

I'm constantly looking at my long trim and short trim (with torque) and on my truck it's always on negative side (the truck run rich over all map and never seams to adjust itself correctly)
On the good truck, both trim are nearly at 0 (the truck doesn't make any adjustment over map).
Now I just need to find why???

My idle is jurking comparing with my friend truck, can it be a bad injector??? really hard to find and dealer will never help me to find this. I changed my airfilter for a k&n dropin but no improvement.

I'm a mechanical engeneer and I know that something wrong with some of our truck, and it can't be only the tire pressure or gas type or some other stupid things. I need to find what it is because this is really not normal. I gladly change my truck for my friend's truck but he doesn't want...


Goodburbon, can you also check strim and ltrim to see if the bad truck is on negative side on constant speed? if so we'll have 2 bads truck with trim in negative side (that can explain the bad MPG because the truck is always trying to adjust a rich mixture) a bad injector can do that, because the computer don't know that the injector is leaking..