04 TB EXT and POOR gas mileage

[RichieT]

Nobody's mentioning gear ratio with their mileage which could be the difference. I'm getting about 16 on the highway with 4.10's.

 

[Wyle]

Getting 14 city and 18 hwy if I use cruise. My suspicion is that 05's are notorious for bad mileage because there was a power increase but no MAF.

In 115k total miles of driving, my '05 has averaged just under 18 mpg.
I drive it like I'm the one paying for that $17,550 worth of gas.

 

[DocBrown]

Driving habits are everything. I've got an EXT, 137k, 20 MPG with E-10 @ 60mph. It drops to 17/18 at 70mph. I average anywhere from 12 - 17 in mixed driving depending on who in my house is driving it. I rarely let it get over 2500 RPMs, so I'm the one who can get 16 in mixed driving pretty easily.

As far as a clogged CAT, its quite possible. Many of the CATs on '02 - '04s get replaced between 75k and 110k. My TB never threw a code, but my thermostat was bad though I didn't realize it. I was just below 12:00 and I thought that was hot enough.

 

[Jkust]

I've been tracking my 9-7x mileage manually since I got it in January. She'll do upwards to 22mpg on the highway on the DIC with about 90% highway driving the manual calculation is alway between 17 and 17.8mpg which is what the DIC sits at if I just let it be. Basically then I get right between the 15 and 20 EPA estimates with almost all highway driving. I've quit driving with a light foot and now almost always drive fast at 70+mph and the calculations barely change.

 

[DenaliHD66]

Nobody's mentioning gear ratio with their mileage which could be the difference. I'm getting about 16 on the highway with 4.10's.

Good point, I have 3.42s and get 14 ish consistently.

Driving habits are everything. I've got an EXT, 137k, 20 MPG with E-10 @ 60mph. It drops to 17/18 at 70mph. I average anywhere from 12 - 17 in mixed driving depending on who in my house is driving it. I rarely let it get over 2500 RPMs, so I'm the one who can get 16 in mixed driving pretty easily.

As far as a clogged CAT, its quite possible. Many of the CATs on '02 - '04s get replaced between 75k and 110k. My TB never threw a code, but my thermostat was bad though I didn't realize it. I was just below 12:00 and I thought that was hot enough.

95k on my original CAT, and I seafoam at every oil change every 6k miles. I had a catback exhaust put on at around 30k miles which I think may extend the life of the cat by reducing a lot of backpressure, but I'm just theorizing.

Anyone have a high flow cat? If so what brand and has it improved anything (horsepower, mpg)?

 

[RayVoy]

How things have changed, when my dad taught me he told to pretent there was a pretty girl in a tight sweater waiting for me to pick her up.

Haha, mine were the pretty girls in the tight sweaters, no boys

 

[Rubberman]

Just drove our family vacation from Indiana to Florida. Which is 605 miles one way. 3rd row seats folded down and packed with suitcases and other crap. I was getting 21.87 mpg. I was going 10mph over the speed limit plus getting stuck in traffic when going thru Nashville. I have 117k miles.

 

[DenaliHD66]

Just drove our family vacation from Indiana to Florida. Which is 605 miles one way. 3rd row seats folded down and packed with suitcases and other crap. I was getting 21.87 mpg. I was going 10mph over the speed limit plus getting stuck in traffic when going thru Nashville. I have 117k miles.

Pretty good. I see you are 2wd too though, which helps a bit. For some reason I've been getting close to 16 mpg lately... and I've had my bearings and cv axles grinding/roaring during the process, so who knows. My local Exxon station transformed into a Marathon, so I stopped going there since I don't get a gas discount, and have just been going to a local gas station where I get earnings from my grocery shopping, and apparently I've been getting better mileage since making the switch over. I was always under the impression Exxon's regular grade gasoline was the best on the market. Also, when I fill up, I set the gas handle to auto fill it up, and even after it shuts off, I let it sit for a good 5-10 minutes, then I "top" it off, which usually another full gallon goes in on the next trigger squeeze. Then I let it sit another 5 minutes, collecting the vapors and last drops, then I pull it out. I think these little things have been beneficial in maximizing gas mileage also.

 

[Spyw]

Might be of interest to some of you. I drive my Envoy for work. 2011 was my first full year of doing it, and I put on about 25k miles. I drive a good mix of city vs highway, but day-to-day I'm primarily just in the city. This year, I drew up a little spreadsheet to keep better track of my cost vs. reimbursement. Right now I'm getting paid $0.40 per mile and spending $0.25 per mile, with $0.21 of that being fuel cost and the rest being repairs.

A couple of notes:
I'm coming up on 127k miles
I have 3.42 gears
I have 4WD
My current tire pressure is 34psi (Going to up to ~38 for road trip coming up)
I'm 23 and drive like I stole it
My tires have about as much tread as racing slicks, so I'm sure their low rolling resistance helps

At ~85k miles, I replaced
-Front O2 (ACDelco)
-Plugs (41-103)
-Thermostat (Had P0128)
-Front Wheel Bearings

At ~95k
-Front Bilstein HD
-MarkMC Lift (Super necessary for me, I know)
-Rear BDS Shocks

At ~100k
-Transfer Case Fluid
-Front Diff Fluid

At ~125k
-Front Brakes
-Full Tie Rods
-CV Axles

 

[DenaliHD66]

I started to do the same, not quite factoring in the cost of the repair aspect but I never got consistent with it. I am at 97k with original plugs and getting better gas mileage that I haven't seen since it was brand new and on OEM size tires. Now I run 255 all terrains... I did up my tire pressure from 30 front 35 rear to 40 all around, so many that is a reason that has helped. Also I have toe-in on my alignment, which could also be improved, and yes I have a heavy foot too on purpose.

Some things I plan on doing shortly this summer are:

Replace spark plugs
Replace both o2 sensors
PCM4LESS E-fan kit, with reflash to 93 premium octane.
CPAS (camshaft solenoid)
Fuel Filter
Upper and lower gas tank hoses
Clean cold air intake and throttle body (which I do 2x a year anyway so its never really that dirty)

 

[Wooluf1952]

Also, when I fill up, I set the gas handle to auto fill it up, and even after it shuts off, I let it sit for a good 5-10 minutes, then I "top" it off, which usually another full gallon goes in on the next trigger squeeze. Then I let it sit another 5 minutes, collecting the vapors and last drops, then I pull it out. I think these little things have been beneficial in maximizing gas mileage also.

That won't make any difference in the final MPG's. You are still adding it in to the equation, unless you're using the average from the DIC (and that is seldom accurate).

 

[DenaliHD66]

That won't make any difference in the final MPG's. You are still adding it in to the equation, unless you're using the average from the DIC (and that is seldom accurate).

I calculate my trip mileage divided by when the pump initially shuts off automatically. After that, I continue to fill up and let the extra run off and vapors go in my tank. I'm not really "topping it off" because when I wait, it pours in another full gallon before shutting off again.

 

[CaptainXL]

I calculate my trip mileage divided by when the pump initially shuts off automatically. After that, I continue to fill up and let the extra run off and vapors go in my tank. I'm not really "topping it off" because when I wait, it pours in another full gallon before shutting off again.

You dont want to do that. Its bad for your evap canister.

 

[DenaliHD66]

My what and where?

 

[Denali n DOO]

You dont want to do that. Its bad for your evap canister.

I definetly agree, I filled mine right up the filler tube on Sunday and for the fist 60km of driving the fuel gauge was messing up, empty-full-empty-full, then SES light. I'll never do that again!!

 

[DenaliHD66]

I've really really topped it off before, in that I kept squirting the gasoline with the nozzle all the way in. I never tried to fill it up to the intake hose though by easing the gasoline nozzle out of the socket. I've never had a problem with Fuel Gauge or any abnormal lights either.

 

[strat81]

You dont want to do that. Its bad for your evap canister.

+1. Topping off the tank on modern vehicles is a bad idea.

The evap canister is part of the emissions system near the fuel tank. It has charcoal in it to capture gasoline fumes. It is purged when the vehicle is running normally. Topping off the tank can fill that canister with liquid fuel which messes up the purge process.

 

[TB2004]

I think its the fuel, all the added ethanol will give lower mileage. If they will make normal fuel again we will all see an increase. Additionally having the same fuel makeup nation wide will have big difference too.

 

[Jake Blazer]

[COLOR="#00FFFF"][/COLOR]my ride gets about 20 hwy 15-16 city. it really sucks. my 350 made in 91 does just as good

 

[IllogicTC]

[COLOR="#00FFFF"][/COLOR]my ride gets about 20 hwy 15-16 city. it really sucks. my 350 made in 91 does just as good

Gear ratio and installed options make a huge difference. Mine has the mid-grade 3.73 axle and nearly every option (just more weight when it comes down to it), I can see up to maybe 20-21 at 55MPH. At 40, I've had it up to 30. This is where my transmission engages the torque converter clutch.

 

[gmcman]

Nobody's mentioning gear ratio with their mileage which could be the difference. I'm getting about 16 on the highway with 4.10's.

Revisited thread but old post, I have the same setup as you but an 02...how fast are driving on the hwy? I get 16 and this is 30 miles each way to work and half of which is stop and go, 1/4 of that is bumper to bumper. Highway I'm getting 21 give or take 1.