Another MPG thread

GTboosted

GTboosted

TJ Enthusiast
Joined
Jun 7, 2018
Messages
256
Location
Los Angeles- The Valley
So I just calculated my mpg and I get 12.02

Mainly highway driving cruising at 60. (Stayed on the right lane on purpose). Flat, no hills.

4.0
Auto 32rh
3.73 gears
31" ko2s
52k miles on the odo

That's on the low end right?

Edit: forgot to add this is based on tank filled to max then driven for 199 miles. Light came on and I filled up again with 16.55 gallons. What tire size is the TJs cluster calibrated too? I'm guessing the original owner did not calibrate the cluster 8k miles ago when he went to a slightly larger tire than stock.
 
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GTboosted said:
So I just calculated my mpg and I get 12.02

Mainly highway driving cruising at 60. (Stayed on the right lane on purpose). Flat, no hills.

4.0
Auto 32rh
3.73 gears
31" ko2s
52k miles on the odo

That's on the low end right?

Edit: forgot to add this is based on tank filled to max then driven for 199 miles. Light came on and I filled up again with 16.55 gallons. What tire size is the TJs cluster calibrated too? I'm guessing the original owner did not calibrate the cluster 8k miles ago when he when to a slightly larger tire than stock.
Click to expand...

You can use a gps app to tell how far off your speedometer is. And it can track your drive mileage to give you a accurate mpg.
 
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You don't calibrate the cluster, you buy a new speedo gear based on tire size and gear ratio.
A properly matched tire and gear size should bring a good running TJ into the 14.5 to 16.2 mpg. That's my range and the advertised range when new.

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2003 ,4.0, 5 speed ,33" KO2 tires.

Just regeared , 4:10 to 4:56

Shocked .

Filled up. Drove 120 actual gps miles . Refueled.

Used 6 gallons of gas....20 mpg. Prior to regear was 13-14.

Mic drop.
 
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GTboosted said:
So I just calculated my mpg and I get 12.02

Mainly highway driving cruising at 60. (Stayed on the right lane on purpose). Flat, no hills.

4.0
Auto 32rh
3.73 gears
31" ko2s
52k miles on the odo

That's on the low end right?

Edit: forgot to add this is based on tank filled to max then driven for 199 miles. Light came on and I filled up again with 16.55 gallons. What tire size is the TJs cluster calibrated too? I'm guessing the original owner did not calibrate the cluster 8k miles ago when he went to a slightly larger tire than stock.
Click to expand...
How's it running? Recent tune? Any codes? Mashing on the gas from every stop? It may only have 52k but it is still older in vehicle years. Your speedo running slower than it should will also skew your results.
 
GTboosted said:
So I just calculated my mpg and I get 12.02

Mainly highway driving cruising at 60. (Stayed on the right lane on purpose). Flat, no hills.

4.0
Auto 32rh
3.73 gears
31" ko2s
52k miles on the odo

That's on the low end right?

Edit: forgot to add this is based on tank filled to max then driven for 199 miles. Light came on and I filled up again with 16.55 gallons. What tire size is the TJs cluster calibrated too? I'm guessing the original owner did not calibrate the cluster 8k miles ago when he went to a slightly larger tire than stock.
Click to expand...
Yeah, I did what @Boinked did using a gps to calculate the difference. I came up with a figure I use every time I fill up; 1.16 x # of mpg to get the real mpg. E,g. If it says 12.02, I multiply by 1,16 and it’s really 13.94. When I get to final tire size I’ll get the proper speedo gear
 
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Rob5589 said:
How's it running? Recent tune? Any codes? Mashing on the gas from every stop? It may only have 52k but it is still older in vehicle years. Your speedo running slower than it should will also skew your results.
Click to expand...

Its running nice. Nice enough that I was calculating the mpg to consider if I can make it my dd.

No codes, no lights in the dash, drives straight. I did all the fluids when I got it, nothing else. What is usually a culprit of lower mpgs? Should I do plugs and wires?

Drove it today again and at 60 my phone showed 63 on a gps app. So even if I was to cruise all the 199 miles at 60 the best mpg I would get is 12.68 (210 miles to 16.55 gallons). I know we don't buy these for their efficiency but 12mpg is pretty bad.
 
GTboosted said:
Its running nice. Nice enough that I was calculating the mpg to consider if I can make it my dd.

No codes, no lights in the dash, drives straight. I did all the fluids when I got it, nothing else. What is usually a culprit of lower mpgs? Should I do plugs and wires?

Drove it today again and at 60 my phone showed 63 on a gps app. So even if I was to cruise all the 199 miles at 60 the best mpg I would get is 12.68 (210 miles to 16.55 gallons). I know we don't buy these for their efficiency but 12mpg is pretty bad.
Click to expand...
So many things can affect your MPG. Quality of gas, plugs, wires, dirty injectors, dirty throttle body, driving uphill.

If it was me i would change plugs and wires first with a new airfilter. (Cheapest)

Then i would run seafoam through the next 3 to 4 tanks of gas - some people say its a waste but my jeep likes it.

But that is just where i would start.


EDIT. Also tire pressure. I run my 33x12.5 at 26psi. It makes the tires wear even but i lose MPG. More ground contact.
 
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GTboosted said:
Just saw the thread you posted. 20 is really good.
Click to expand...
I'm astounded and honestly wouldn't even believe it if I hadn't seen it myself.
I'm sure running without the front driveshaft helped
 
GTboosted said:
So I just calculated my mpg and I get 12.02

Mainly highway driving cruising at 60. (Stayed on the right lane on purpose). Flat, no hills.

4.0
Auto 32rh
3.73 gears
31" ko2s
52k miles on the odo

That's on the low end right?

Edit: forgot to add this is based on tank filled to max then driven for 199 miles. Light came on and I filled up again with 16.55 gallons. What tire size is the TJs cluster calibrated too? I'm guessing the original owner did not calibrate the cluster 8k miles ago when he went to a slightly larger tire than stock.
Click to expand...
That's very low.
 
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20180905_173521.jpg


The rpms seem a bit high at this speed no... Or is it normal for the 3 speed?
 
Boinked said:
I think you are right in the sweet spot. But that is my opinion.
I do not believe the 4.0l does good at low 2k rpm under load. I have read many articles about buildup of carbon under low rpm loaded conditions.
Click to expand...

Yeah not worried about damaging anything with high or low rpms. Just trying to figure this out.

Since I am getting about 12mpg with 31s it didnt make sense. Specially since @AndyG got 20. I thought I should be somewhere in between. Not thinking about gas cost since this is my 3rd vehicle. Just want it to run optimal. I'll take your suggestion and start with plugs and wires.
 
4.0 , 5 spd, 3.07, 235r75x15 tires. 2700 @75 mph. 16+/- mpg @ best. All new fluids, ignition (plugs, wires , cap, rotor, distributor, new injectors, air and fuel filters (not the in tank one) tires checked every month. Can't squeeze another mpg out of her to save my life.....

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Ok based on a bit more research I will also replace the upstream 02 sensor. I think I only need one. Thanks to a comment by @Jerry Bransford

This is the comment I found in the "other" forum.
"Your '97 has two 02 sensors and only the upstream 02 sensor (located just below the header) could cause that issue. In other words the downstream 02 sensor on the catalytic converter doesn't need to be changed. The odds the upstream 02 sensor being the cause of your suddenly poor mpg are very good."
 
fxrsliberty said:
4.0 , 5 spd, 3.07, 235r75x15 tires. 2700 @75 mph. 16+/- mpg @ best. All new fluids, ignition (plugs, wires , cap, rotor, distributor, new injectors, air and fuel filters (not the in tank one) tires checked every month. Can't squeeze another mpg out of her to save my life....
Click to expand...
That's great mpg.
 
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