Solid 19.5 mpg. Am I doing something wrong?

NerdNoise · 08-13-09, 06:02 AM

So I get a steady 19.5 mpg on long haul @ 65 mph with or without the AC. wife, 2 kids, and crap in the back (5780 lbs. at a weight station).

Around town I get 17.5 or so. So, with all of this "12 mpg WHOA!!!" going around, makes me think: Am I doing something wrong here?

It's pretty much stock as far as the power train goes, tires as well. I run 5-30 Mobile1 and standard ATF. I do have a vacuum gauge and I do tend to somewhat drive by that. Maybe that's it?

ToothDr · 08-13-09, 06:17 AM

Hmmm, I've never heard of an 80 getting 17.5 MPG around town.
I get 14 MPG around town and I thought I was doing great.
You dont have a diesel conversion do you?

Pete

NerdNoise · 08-13-09, 06:41 AM

No diesel here. I do run the tires at roughly 90 psi though. Does that help?

Kaoscruizer · 08-13-09, 06:59 AM

I am interested in this conversation .. I am pretty sure I just LOST 30 miles per tank starting last week! Not sure what happened, but would like to have some long time owner check in here. No mods since then, only the installation of my blue fan clutch. No CEL's

slow91fj90 · 08-13-09, 07:13 AM

What do you mean by, I drive with vacuum gauge?

firetruck41 · 08-13-09, 08:16 AM

Don't take this wrong, but how do you calculate your gas mileage?

GLTHFJ60 · 08-13-09, 08:39 AM

90 psi? Holy crap.

sailor · 08-13-09, 08:53 AM

I get worse with the diesel. Post up the calculation details?

mmuthart · 08-13-09, 08:54 AM

Quote:

Originally Posted by GLTHFJ60

90 psi? Holy ****.

X2! xxxxxx

cpg · 08-13-09, 08:56 AM

Quote:

Originally Posted by NerdNoise

No diesel here. I do run the tires at roughly 90 psi though. Does that help?

I am sure 90 psi would get you better mileage than 30 psi. What kind of tires and what is the max pressure from the manufacture? Seems like 90 psi may be unsafe for the stock tires.

spdwaver1 · 08-13-09, 08:59 AM

90 psi: You may as well be running poly-filled forklift tires.

Is the center line of your tread getting worn faster than the sides?

Arleaux · 08-13-09, 09:21 AM

GotCone? · 08-13-09, 09:28 AM

I'm hopeful his 90 psi is a joke.

d0ubledown · 08-13-09, 09:32 AM

post up how you calculate...as 17.5 for city is a lil far fetched for a 5000lb AWD truck. 90psi would be a tad bit unsafe IMO...

regardless...good on ya for getting such unreal mileage! i average about 15 hwy, thats running as light as i can without 3rd row or spare, but with 315's, bumper & sliders.

Ebag333 · 08-13-09, 09:37 AM

I don't think 19.5 MPG is impossible, I was getting almost 16 in my truck when it was stock.

Take off the rust rack for another .5-1 MPG. Run premium for another 1-2 MPG. Run 90 PSI for the other 1-3 MPG.

ToothDr · 08-13-09, 11:06 AM

I think he's kidding about the 90 psi, at least I hope he is.
The max amount of pressure for a stock 80 tire size is around 50 psi I think.

Pretty sure you would blow the tire out at 90 psi

fzjconvert · 08-13-09, 11:11 AM

Quote:

Originally Posted by d0ubledown

post up how you calculate...as 17.5 for city is a lil far fetched for a 5000lb AWD truck. 90psi would be a tad bit unsafe IMO...

regardless...good on ya for getting such unreal mileage! i average about 15 hwy, thats running as light as i can without 3rd row or spare, but with 315's, bumper & sliders.

I too would like to see how you calculate mileage! I think the question should be what are the reat of us doing wrong?

Quote:

Originally Posted by Ebag333

I don't think 19.5 MPG is impossible, I was getting almost 16 in my truck when it was stock.

Take off the rust rack for another .5-1 MPG. Run premium for another 1-2 MPG. Run 90 PSI for the other 1-3 MPG.

Like wise! I have seen over 17 on the long haul but around town

I even have to admit I run my tires around 50psi but they are rated for 65psi Unless your are running some real expensive commercial tires be real careful at 90 psi. I would hate to hear that you had an accident and you family got hurt!

e9999 · 08-13-09, 11:28 AM

when stock, IIRC, I was doing about 17 on the freeway driving at 55/60

never got close to 19 sadly enough

I'm running 50 psi or so when I want to save gas, which is close to the limit stamped on my MT/Rs

now, with armor and junk, it's more like 14 on the freeway

hawkeye · 08-13-09, 11:49 AM

I think he regeared to 5.29s and runs 31s and did not correct the speedometer.

NerdNoise · 08-13-09, 12:14 PM

Ok. The whole 90 psi is just a joke. I read those dudes in the small cars that try to hypermile put on really skinny tires and inflate them as if they were bike tires. I run 265/75/16 @ 35 psi or so. As far as the fuel calculation goes, I learned in junior high that to get a miles per hour calculation you take the miles driven and divide by the gallons used. Simple math.

Now that I think about it my "around town" includes about 13 miles each way on the highway to get to the city driving. So maybe I spend a bit more time at a solid 60 mph than I thought.

NerdNoise · 08-13-09, 12:19 PM

As far as the vac gauge, it shows essentially among other things engine load. As I drive I keep an eye on the engine load and I am mindful of what "tasks" are engine load expensive. Like passing uphill etc.

COLX450 · 08-13-09, 12:27 PM

I have a 97 LX with 167K and VERY consistently get 16.5mpg. I have a daily commute of 30 miles...18 or so highway the rest city. The worst I have calculated since purchasing the beauty in april was 14.9mpg...and that was with 50+ miles on rough 4x4 roads....but coming back down into Denver I was pretty much coasting

I also read all this about 12mpg and wonder what I am doing wrong. When I filled up yesterday....18.85 gallons....311 miles on the trip = 16.50mpg. She is all stock! I even have an exaust leak that needs fixed.