Topic: Gas Mileage Thread

[chardrc]

Does your state switch over to a 'Winter Blend'?  If it does, then that's the reason.  Also, during winter, people use their heaters, wipers and lights more often which causes the alternator to charge more.  Although, I doubt that's measurable/

the mpg is lost in the motor not being warmed up (as fast) resulting in a richer fuel ratio and a slightly higher idel... and when its really cold and i have to sit and let it warm up

[indyjeepnut]

Debating on 456 or 488... 2.5 ax5 31's anyone running either of these combo's. With 488 I should be tacking 3k @ 65mph. 456 should be 2600. Which would be better gas mileage for street driving? From what I have read the 2.5 like to run around 3k.

Give me your thoughts

[FourbangerYJ]

Tranny = AX5
Motor = 2.5L MPFI
Tire size = 37 (32psi)
Gearing = 5.38
Checked my speedo with a GPS it's on the money!
Engine mods = Rockit City intake tube with K/N. 4.0TB non bored intake. Flowmaster 50 series muffler.

My last run I checked my mileage. I got 12.9 MPG. This is doing 65-70 MPH thru some hills and flat HWY. I  real hard when one of the guys running a 4.0 XJ told me I was driving to fast and to keep it under 65MPH!

When I was running 4.88's and 35's I was getting about 10 MPG.

When I bore the intake and add the 62mm TB I will update.

Update With the 62MM TB I got 13.8 MPG. I drove the same route as my last gas mileage post.

[TahoeYJ]

Filled up the other day and I've kept my foot out of the skinny pedal as much as possible to see what kind of mileage I truly get out of a tank. Granted this tank will be like 95% city driving, I'm anxious to see what I get, as my gas guage seems to be moving at a nice, slow rate 

Sometimes I forget how much better mileage I get when I don't drive the piss out of it 

[aka-justin]

I get about 15 MPG in my 1995YJ.

AX5
2.5L 4 Banger!
31x12.5xR15 ProComp Mud Terrians
Stock 4.11 Gearing
No Speed Calibration, only off by 1 mph per 15.  When I'm doing 60 per the gauge, I'm going 64-65.
Only upgraded the TB to a 4.0 and did a tune up. (Spark Plugs, Oil and Filter, Air Filter, Fuel Filter, and Diff./Transmission/Axle Fluid Change)

[dexetr30]

My mileage is slowly making it's way back up to where it should be during the warmer months. I figure it's due to not having to warm it up for 10 minutes every morning and not having it in 4wd all the time.

Maybe I'm crazy but it seems like my mileage sucks when I use gas with 10% ethanol in it. Does this happen to anyone else?

[FourbangerYJ]

Mileage went down to just over 11. The only thing I changed was swapping the soft top for a bikini and taking the K&N/Rockit city air intake tube off and swapping in a OE TJ intake box.
How much areo loss is there by going from a soft top to a bikini?

[Jeffy]

Mileage went down to just over 11. The only thing I changed was swapping the soft top for a bikini and taking the K&N/Rockit city air intake tube off and swapping in a OE TJ intake box.
How much areo loss is there by going from a soft top to a bikini?

A lot.  There is too much turbulence with no top or bikini top on.  Air gets sucked back into the Jeep from behind, air getting sucked in from the sides, etc...   I noticed a difference in mileage when I went from Soft top to a hard top even though the hardtop adds weight.  The hardtop has a slicker surface so there is less for teh wind to grab, not to mention it's 2" shorter then the softtop.  The softtop inflates at higher speeds which also increases it's size.  The flapping doesn't help either.  BUT this is at higher speeds.  Aerodynamics come into play at speeds higher then 35MPH.  At 55MPH it's not too bad, even 60MPH but start pushing it to 70 or higher and you'll start to hit the proverbial brick wall.

I've mentioned this before but I played around, removing a bunch of weight and noticed no difference at highway speeds in mileage.  I removed my rear bumper, rear seat, spare, spare mount, passenger side mirror, winch, winch plate, aux lights etc and noticed very little is any difference at highway speeds.  I did notice it was quicker from a stand still.

Also when I was playing around with the intake and exhaust, I noticed I have more torque with the stock air box and my Borla.  I was running a K&N open element and I was able to REV more freely but there wasn't as much torque at the low or mid.  I had more HP at the top end though.  I also noticed when I punched a 2" tear in my exhaust right after teh muffler,  I had less torque but had more HP at the top end.  It was enough to feel the difference.

[Jeffy]

Maybe I'm crazy but it seems like my mileage sucks when I use gas with 10% ethanol in it. Does this happen to anyone else?

Yes, ethanol reduces your mileage.

[jfrabat]

Yes, ethanol reduces your mileage.

Correct; ethanol has less energy than gas, hence you need to consume more to get the same power...

[FourbangerYJ]

A lot.  There is too much turbulence with no top or bikini top on.  Air gets sucked back into the Jeep from behind, air getting sucked in from the sides, etc...   I noticed a difference in mileage when I went from Soft top to a hard top even though the hardtop adds weight.  The hardtop has a slicker surface so there is less for teh wind to grab, not to mention it's 2" shorter then the softtop.  The softtop inflates at higher speeds which also increases it's size.  The flapping doesn't help either.  BUT this is at higher speeds.  Aerodynamics come into play at speeds higher then 35MPH.  At 55MPH it's not too bad, even 60MPH but start pushing it to 70 or higher and you'll start to hit the proverbial brick wall.

I've mentioned this before but I played around, removing a bunch of weight and noticed no difference at highway speeds in mileage.  I removed my rear bumper, rear seat, spare, spare mount, passenger side mirror, winch, winch plate, aux lights etc and noticed very little is any difference at highway speeds.  I did notice it was quicker from a stand still.

Also when I was playing around with the intake and exhaust, I noticed I have more torque with the stock air box and my Borla.  I was running a K&N open element and I was able to REV more freely but there wasn't as much torque at the low or mid.  I had more HP at the top end though.  I also noticed when I punched a 2" tear in my exhaust right after teh muffler,  I had less torque but had more HP at the top end.  It was enough to feel the difference.

Good to know. I have run the bikini for so many years all year, then last fall I got a soft top. Good info THANKS!
Interesting on the weight study. I thought for sure that on the top end a lighter Jeep would beable to have a higher top speed. Make sense getting off the line.
I have always gotten fairly low mileage around 10. I was kinda shocked that I was getting in the 13's. I had not realized that the type of top you run makes such a differance in mileage.

[Bill M.]

A lot.  There is too much turbulence with no top or bikini top on.  Air gets sucked back into the Jeep from behind, air getting sucked in from the sides, etc...   I noticed a difference in mileage when I went from Soft top to a hard top even though the hardtop adds weight.  The hardtop has a slicker surface so there is less for teh wind to grab, not to mention it's 2" shorter then the softtop.  The softtop inflates at higher speeds which also increases it's size.  The flapping doesn't help either.  BUT this is at higher speeds.  Aerodynamics come into play at speeds higher then 35MPH.  At 55MPH it's not too bad, even 60MPH but start pushing it to 70 or higher and you'll start to hit the proverbial brick wall.

I've mentioned this before but I played around, removing a bunch of weight and noticed no difference at highway speeds in mileage.  I removed my rear bumper, rear seat, spare, spare mount, passenger side mirror, winch, winch plate, aux lights etc and noticed very little is any difference at highway speeds.  I did notice it was quicker from a stand still.

Also when I was playing around with the intake and exhaust, I noticed I have more torque with the stock air box and my Borla.  I was running a K&N open element and I was able to REV more freely but there wasn't as much torque at the low or mid.  I had more HP at the top end though.  I also noticed when I punched a 2" tear in my exhaust right after teh muffler,  I had less torque but had more HP at the top end.  It was enough to feel the difference.

Sorry to bring up an old thread, but why did you induce an exhasut leak?? I would think a small horsepower gain for a exhasut leak wouldnt be a good idea!

[Jeffy]

Sorry to bring up an old thread, but why did you induce an exhasut leak?? I would think a small horsepower gain for a exhasut leak wouldnt be a good idea!

I did not induce one it just sort of ripped open.     Ended up with a 2" tear, 1/2" wide in the pipe right after the muffler.  It wasn't ideal since the increase of HP was at the expensive of low end torque.

[chrisfranklin]

My 4Banger can now "out-drink" a big V8! 

[spoonman]

since gas has been cheap all summer, i have been driving my jeep for my daily commute. it's 100 miles with mostly highway. i've not been easy on it and going 70+ on the freeway. i'm still getting 19.5. i think this week i'll try hypermiling the jeep. my jeep is stock except for panel filter and cat back. eventually i'll get a 4.0 tb when davey's gets one in. the tires are stock too.  it's not an offraod jeep b/c i need it as a 3rd vehicle. it gets alot worse mileage than my hyundai accent (46) , but is something a can live with.