Fuel economy

Thunderhead

Thunderhead

All graves go unvisited in time
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Orland, CA, United States
So a few weeks ago we went wheeling in the snow and I got a real heavy foot with the gas in 4 low and we did a few trails we shouldn’t of been on. So, I was getting 16-18 mpg now I’m down to 12-13 mpg. 3 full ups since the snow run.
4.0 I-6 on 32’s.
I’m thinking an evap leak? I will get under the hood and snoop around. Check O-2 sensor maybe check the spark plugs. I think it is running rich though no changes in the way the engine sounds to me.
It hasn’t thrown a code so.... any insight is welcomed
 
yeah, pretty consistent, no idea why, been driving for 50 years, long before a computer controlled mixture. Always got better milage after the snow was gone.
 
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Yeah. Gas is not friendly with the 4.0. Below is my log at every fill up:

12.68 mpg. 12/15/17
15.43 mpg. 12/19/17. 186.2 mi on 12.064gal
11.89 mpg. 12/29/17. 177.3 mi on 14.902gal
(Did use 4wheel Hi for part of it)
12.80 mpg. 01/03/18. 169.3 mi on 13.231gal
12.13 mpg 01/07/18. 125.3 mi on 10.33gal
13.41 mpg 01/12/18 164.8 mi on 12.28gal
12.62 mpg 01/18/18 171.6 mi on 13.59gal
16.47 mpg 01/22/18 217.9 mi on 13.23gal
14.48 mpg 01/28/18 213.3 mi on 14.73gal
14.04 mpg 02/05/18 203.8 mi on 14.51gal
12.25 mpg 02/13/18 175.4 mi on 14.31gal

Current Running Average = 13.47 mpg

You can tell when I had more highway miles!!! When it dropped below 12mpg, it was because I used 4wheel drive quite a bit.
 
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Thunderhead said:
So a few weeks ago we went wheeling in the snow and I got a real heavy foot with the gas in 4 low and we did a few trails we shouldn’t of been on. So, I was getting 16-18 mpg now I’m down to 12-13 mpg. 3 full ups since the snow run.
4.0 I-6 on 32’s.
I’m thinking an evap leak? I will get under the hood and snoop around. Check O-2 sensor maybe check the spark plugs. I think it is running rich though no changes in the way the engine sounds to me.
It hasn’t thrown a code so.... any insight is welcomed
Click to expand...
What's your problem?
 
BayTJ said:
Yeah. Gas is not friendly with the 4.0. Below is my log at every fill up:

12.68 mpg. 12/15/17
15.43 mpg. 12/19/17. 186.2 mi on 12.064gal
11.89 mpg. 12/29/17. 177.3 mi on 14.902gal
(Did use 4wheel Hi for part of it)
12.80 mpg. 01/03/18. 169.3 mi on 13.231gal
12.13 mpg 01/07/18. 125.3 mi on 10.33gal
13.41 mpg 01/12/18 164.8 mi on 12.28gal
12.62 mpg 01/18/18 171.6 mi on 13.59gal
16.47 mpg 01/22/18 217.9 mi on 13.23gal
14.48 mpg 01/28/18 213.3 mi on 14.73gal
14.04 mpg 02/05/18 203.8 mi on 14.51gal
12.25 mpg 02/13/18 175.4 mi on 14.31gal

Current Running Average = 13.47 mpg

You can tell when I had more highway miles!!! When it dropped below 12mpg, it was because I used 4wheel drive quite a bit.
Click to expand...
and so what's your problem? :biggrin:
 
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You must be driving all downhill with the wind at your back.....no need to start yanking 02's.
Welcome to TJ country.
 
Whats incredible is the 4.2L always delivered about 25mpg. I've had 3, in a YJ, a CJ and an AMC. They all could deliver 25mpg on a good day. And the YJ had the Peugeot 5 speed with a 3.07 running 33s. 25mpg was common on the highway at 70mph. I cannot think of anything my 4.0L does better.
 
15192730137681583783909.jpg


You could always drive a Prius
 
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TJ2 said:
What's your problem?
Click to expand...

Drastic drop in mpg. I paid attention to my mpg on almost every fill up for 4 years. Cross country trips and I’m watching my mpg. So I’m fairly sure something is off.
Once I get it figured out I wil report back.
 
Thunderhead said:
Drastic drop in mpg. I paid attention to my mpg on almost every fill up for 4 years. Cross country trips and I’m watching my mpg. So I’m fairly sure something is off.
Once I get it figured out I wil report back.
Click to expand...
I have OEM with 31" KO2 tires and it varies as well due to road conditions.
For 10 months without thinking about it, I saw the average of 18 MPG in my cluster.
 
K well since it’s late and I’m up. Triple checked everything and solved the puzzle. User error. I was running way to low on my air pressure plus the temp went from 70/40 to 50/28 hi-low. All is well and back to normal shitty mph :cool:
 
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