Author Topic: Gas Mileage Thread  (Read 65221 times)

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Offline Jeffy

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Re: Gas Mileage Thread
« Reply #255 on: August 22, 2011, 05:31:02 PM »
I knew if I slowed down I would get better mileage. While convoying with another Jeep we averaged between 60-65 (2700-2800 RPM) miles per hour. I got 17.3 MPG loaded to the gills and climbing the Grapevine from L.A. towards Fresno. I had no idea that 500 RPM would make such a huge change. Last time I did this trip a few weeks ago I was just as loaded and averaged 11.5 MPG while doing 70+ and 3200 RPM.
Wind resistance/aerodynamics comes into play at speeds above 35MPH and increase exponentially.  Dropping down from 70mph to 60mph makes a huge difference.  Drop down to 50-55mph and you'll see more gain.
« Last Edit: August 22, 2011, 05:51:18 PM by Jeffy »
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

road2damascus

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Re: Gas Mileage Thread
« Reply #256 on: August 23, 2011, 08:13:26 AM »
Wind resistance/aerodynamics comes into play at speeds above 35MPH and increase exponentially.  Dropping down from 70mph to 60mph makes a huge difference.  Drop down to 50-55mph and you'll see more gain.

I have the option of driving to work on the expressway @ 55mph (around 2500rpm in fifth) or taking side streets @ up to 45 mph (never over 2000rpm). I have tried both ways with full tanks of gas. There is a huge difference in MPG. Never getting past 2000 rpm for long distances sucks a lot less fuel. The other day I was going 70 mph @ 3500rpm and I could look down every five minutes and see the gas gauge go lower and lower.

Offline chardrc

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Re: Gas Mileage Thread
« Reply #257 on: August 23, 2011, 12:36:30 PM »
The other day I was going 70 mph  (at)  3500rpm and I could look down every five minutes and see the gas gauge go lower and lower.

I have watched my gas gauge go down almost a quarter tank on my drive home when I go over 70mph.  :yikes:... speed definitely makes a difference. couldn't imagine going any real distance with all under 2000 rpm. my jeep doesn't come to life until 2000k (aka if you want to have a chance to maintain speed on a hill in 4th) and gets nice around 2500rpm.
1990 YJ 4cly, ax5, 2.5 inch BDS lift, 31 MTr\'s,  Powertrax-lockers all around, track-bars removed, boomerang shackles, warn m8000 winch, electric fan. [sold but not forgotten]

2007 jk Rubicon 2dr

Higgs

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Re: Gas Mileage Thread
« Reply #258 on: August 23, 2011, 01:31:04 PM »
couldn't imagine going any real distance with all under 2000 rpm. my jeep doesn't come to life until 2000k (aka if you want to have a chance to maintain speed on a hill in 4th) and gets nice around 2500rpm.
I could barely hold my speed at 2k and definitely could not accelerate from those rmps. Now that I have the 4.0L throttle body it at least doesn't feel boggy. I need a good flat surface to drive around 2k and certainly no less than that.

road2damascus

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Re: Gas Mileage Thread
« Reply #259 on: August 23, 2011, 07:42:22 PM »
Chicago-land is flat. I shift after 2000 rpm. On hills I down shift. With stock gears, 30" tires and modifications it does fine. Last MPG uncorrected was 17.7 uncorrected for the tires.

reddogg

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Re: Gas Mileage Thread
« Reply #260 on: August 23, 2011, 09:04:25 PM »
Just go back from a trip from Delaware to Tennessee.95 Jeep 2.5L got 21.6 mpg down and back. stock 225/15 tires. stock 410 gears.  I was getting between 16 and 18 before installing electric fan and 4.0tb.

Torch_Ind

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Re: Gas Mileage Thread
« Reply #261 on: August 24, 2011, 03:43:41 PM »
Just go back from a trip from Delaware to Tennessee.95 Jeep 2.5L got 21.6 mpg down and back. stock 225/15 tires. stock 410 gears.  I was getting between 16 and 18 before installing electric fan and 4.0tb.

nice!! shows improvement with the mild upgrades

chuck172

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Re: Gas Mileage Thread
« Reply #262 on: November 19, 2012, 04:44:27 PM »
Very pleasantly surprised. I checked my mpg today for the first time ever. 22mpg. Didn't go over 60, new stock tires 215/75/15.
4.0, auto 3.07 rear.

Offline sharpxmen

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Re: Gas Mileage Thread
« Reply #263 on: November 20, 2012, 07:49:14 AM »
Very pleasantly surprised. I checked my mpg today for the first time ever. 22mpg. Didn't go over 60, new stock tires 215/75/15.
4.0, auto 3.07 rear.

how did you check your mpg?
'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
Latest: Corbeau BajaRS heated seats :dance: keeping warm the rear end

Da_Skunk

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Re: Gas Mileage Thread
« Reply #264 on: November 20, 2012, 12:32:33 PM »
Last tank was 13 mpg. I forgot to flash the computer after putting in 19lb injectors.  Stock 2.5 squirrels. Aerodynamics are shot I've got a light bar that is helping kill my mpg.

Offline sharpxmen

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Re: Gas Mileage Thread
« Reply #265 on: November 20, 2012, 02:26:11 PM »
yeah, i'm not sure how chuck got his mpg calculated, it's not gallons/mile  :roflol:

guidelines for calculating correct mpg
 - to calculate mpg accurately top-up the tank, reset the trip or write down the odometer reading and drive a bunch, then top-up again and calculate the number of miles driven
 - pay attention on how the Jeep is positioned at the gas pump, the YJ/TJ gas tank is notorious for having differences while not level, best to average the mpg over several tanks to avoid errors.
 - use the numbers behind the decimal point (10.999 gallons is just that and not 10 gallons)
 - calculate mpg like this mpg=<miles_driven>/<gallons_including_decimal_places>

common errors when calculating mpg that result in ridiculous numbers:
 - if your tank shows 3/4 full it doesn't mean you only used 5 gallons (or whatever a 1/4 means in your case)
 - do not count the miles while it's been towed
 - if only driven on the highway with favorable wind the Jeep acts like a big sail, if you want to make it accurate drive the same distance back and re-calculate, better to average mpg over several tanks
 - doesn't count if driven down the mountain, you need to calculate both ways, same thing here - average works better
 - i'm sure there's other factors that I can't think of, feel free to contribute :lol:
 - EDIT: i remembered another one - larger tires without speedo recalibration can result in lower calculated mpg than actual, going the other way are smaller diameter tires or "longer" Ring & Pinion kits (odo/speedo showing more than actual speed/miles driven)
 - EDIT2: another one - doesn't count either if you draft a trailer, big truck or farm vehicles, it's your skill and patience and not real mpg.

if you're sure the Jeep is really good on gas then take the motor out and install it in a Smart car or a Fiat 500, it will get better mpg than the original and be as fast as a Corvette :lol:

if in doubt you can always check the published numbers, if you're off by too much might want to review the calculations http://www.fueleconomy.gov/feg/noframes/19193.shtml
« Last Edit: November 20, 2012, 02:49:23 PM by sharpxmen »
'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
Latest: Corbeau BajaRS heated seats :dance: keeping warm the rear end

chuck172

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Re: Gas Mileage Thread
« Reply #266 on: November 20, 2012, 06:41:37 PM »
I filled up, traveled 163 miles, came back to the same station and filled again. I divided the gallons it took into  the miles I traveled. Came out to 22. I was stunned. I'll be rechecking from time to time to verify.

Offline sharpxmen

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Re: Gas Mileage Thread
« Reply #267 on: November 20, 2012, 08:11:23 PM »
chuck, sounds like you did it the right way, if that is indeed the correct mpg you get the Wrangler platinum award for saving fuel. I'd be interested to see the next tank where you're at (as in from the last fillup since you calculated the mpg).
« Last Edit: November 20, 2012, 08:12:34 PM by sharpxmen »
'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
Latest: Corbeau BajaRS heated seats :dance: keeping warm the rear end

Offline Mozman68

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Re: Gas Mileage Thread
« Reply #268 on: November 21, 2012, 03:13:11 AM »
Have been checking mine after full fill ups since I changed tires a couple of months ago...getting right around 14 mpg on average...sometimes 14.5 if the wind is on my side, sometimes 13.8 at the lowest....

37" tires with 4.88 gearing....about 70 miles of highway a day, 5 days a week...bah.
2009 Audi S5....what....its 4wd...sort of....

Offline Jeffy

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Re: Gas Mileage Thread
« Reply #269 on: November 21, 2012, 11:52:58 AM »
I've been getting 16-18 mpg city.  Lots and lots of short 12 mile trips.  I still don't do much of any highways on a regular basis.  I think what I have done matches the city mileage as I'm unable to predict the route before hand.  I might also need to tweak the air box a bit.  I have it setup for more top end and less bottom.  I was also doing 70-75 mph. which didn't help.
« Last Edit: November 21, 2012, 11:53:54 AM by Jeffy »
Youtube Channel: https://www.youtube.com/channel/UCZNlr60GXH5OlKIFrT7P6mg
My Jeep: http://4bangerjp.com/forums/index.php?topic=2783.0
"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."