Gas mileage in the crapper...

jdumont · **Posted:** Sat Jan 05, 2008 2:53 pm

So Ive never really gotten good mileage but it seems to be getting worse lately. I know winter gas is to blame, as is my ARB, and all terrain Kumhos, and all the herculiner grabbing the wind.... lol. But really should I be only getting 200 miles on a full tank before my gas light comes on? Thats with no 4x4 driving and only doing 65mph on the highway... I also have a K&N and a Flowmaster super 40 (going back to stock very soon).

Anyone?

Hood297 · **Posted:** Sat Jan 05, 2008 3:07 pm

I can usually squeeze about 225 out of one tank with and ARB 245/75 mtr's light bar and dual air intake and flowmaster super 40. I rarely drive above 55 and have noticed once you hit that mark the MPG's begin dropping dramatically.

Aerodynamics really start coming in to play at 65+.

Guest · **Posted:** Sat Jan 05, 2008 3:14 pm

All the reasons listed on this active post.

jdumont · **Posted:** Sat Jan 05, 2008 3:23 pm

I guess it is the aeros. I always thought that going at 65 would be more efficient because thats when the last gear locks up and the revs are the lowest? Maybe that isnt enough to overcome the aerodynamic losses from the extra 10mph. Ill give it a try this week, thanks!

Hood297 · **Posted:** Sat Jan 05, 2008 3:27 pm

I've found that low RPM's (1000-1400) on this engine are bad. Its much more happy at 1500-2000.

PaU-MWolverine · **Posted:** Sat Jan 05, 2008 4:07 pm

Join the club... I also get only 200 - 225 mi per tank.

Reasons are many, as listed in this and other posts.

M&P40 · **Posted:** Sat Jan 05, 2008 6:04 pm

happy to hear i am not the only one

sad being i have a 20 GAL tank and get 220 - 250 a tank

tjkj2002 · **Posted:** Sat Jan 05, 2008 6:19 pm

Anytime you lift a vehicle your going to loose mpg's,anytime you put bigger then stock tires on your going to loose mpg's,and anytime you add wieght(armor,skids,rockrails,and such) your going to loose mpg's.If you don't want to loose mpg's return to stock or stop complaining,you have to pay to play.You want bad mileage try my KJ out for awhile,only about 140 miles(winter gas,all city driving in the mountains) to the tank,but I'm not complaining,it's a Jeep and I modified it so I accepted the bad mileage.

Oh and not regearing after a tire change is the biggest looser of mpg's,need to regear but to bad you can't regear properly after 30" tires in the KJ.SFA hear I come!!!!!!!!

Albert · **Posted:** Sat Jan 05, 2008 6:36 pm

Welcome to the world of jeep.

When I leave mine in the garage and drive the Cutlass, I get 28-30mpg, but it won't go over a speed bump in a parking lot at more than 2mph without hitting the front spoiler.

Hood297 · **Posted:** Sat Jan 05, 2008 7:00 pm

tjkj2002 wrote:

Anytime you lift a vehicle your going to loose mpg's,anytime you put bigger then stock tires on your going to loose mpg's,and anytime you add wieght(armor,skids,rockrails,and such) your going to loose mpg's.If you don't want to loose mpg's return to stock or stop complaining,you have to pay to play.You want bad mileage try my KJ out for awhile,only about 140 miles(winter gas,all city driving in the mountains) to the tank,but I'm not complaining,it's a Jeep and I modified it so I accepted the bad mileage.

Oh and not regearing after a tire change is the biggest looser of mpg's,need to regear but to bad you can't regear properly after 30" tires in the KJ.SFA hear I come!!!!!!!!

What would be regearing properly? lower than 4.10 to keep near stock?

tjkj2002 · **Posted:** Sat Jan 05, 2008 7:04 pm

Hood297 wrote:

tjkj2002 wrote:

Anytime you lift a vehicle your going to loose mpg's,anytime you put bigger then stock tires on your going to loose mpg's,and anytime you add wieght(armor,skids,rockrails,and such) your going to loose mpg's.If you don't want to loose mpg's return to stock or stop complaining,you have to pay to play.You want bad mileage try my KJ out for awhile,only about 140 miles(winter gas,all city driving in the mountains) to the tank,but I'm not complaining,it's a Jeep and I modified it so I accepted the bad mileage.

Oh and not regearing after a tire change is the biggest looser of mpg's,need to regear but to bad you can't regear properly after 30" tires in the KJ.SFA hear I come!!!!!!!!

What would be regearing properly? lower than 4.10 to keep near stock?

30" tires=4.10's,31" tires=4.30,and 32" tires=4.56's.

Hood297 · **Posted:** Sat Jan 05, 2008 7:14 pm

How accurate do you think this table is just for future reference? http://www.4lo.com/calc/geartable.htm

tjkj2002 · **Posted:** Sat Jan 05, 2008 7:21 pm

Hood297 wrote:

How accurate do you think this table is just for future reference? http://www.4lo.com/calc/geartable.htm

That's a good general start,but that is stated for a manual tranny with a top gear of 1:1,but gives a good starting point.With the lack of low rpm torque that the 3.7 produces I would stick to the higer end if not the red zones to maximize the 3.7's torque range.Just remember that at the rpm at which a engine produces it's max torque the engine is also at it max effeciancy,keeping close to that max torque rpm will gain the best performance and mpg's.

Hood297 · **Posted:** Sat Jan 05, 2008 7:25 pm

so 4.56 (if possible) would be better for gas mileage than 4.10 with 265-75-16's? obviously good for torque, but I always thought it was a trade off especially around 55+

DryBones · **Posted:** Sun Jan 06, 2008 11:20 am

It's big oil finding another way to get more of your money. They have changed the formula so that KJ's use more gas. ONce it's up to $6 a gallon they will change the formula back. :twisted:

dloc_jeep_KJ · **Posted:** Sun Jan 06, 2008 11:46 am

DryBones wrote:

It's big oil finding another way to get more of your money. They have changed the formula so that KJ's use more gas. ONce it's up to $6 a gallon they will change the formula back. :twisted:

wouldnt suprize me one bit :lol:

myjeepwalks · **Posted:** Sun Jan 06, 2008 5:07 pm

I get about 200-220 per tank. 50/50 hwy and city. At 80+mph on the hwy it really sucks the gas down. There are some people that claim 20+ mpg's on a gasser. :roll:

jerseykj · **Posted:** Sun Jan 06, 2008 7:21 pm

wow i must have a special jeep or somethin. i've been getting 300+ around town and alot more on the hiway. and i have a gas engine with the 3.7 and a k&n. it is all stock...for now.

tjkj2002 · **Posted:** Sun Jan 06, 2008 7:26 pm

jerseykj wrote:

wow i must have a special jeep or somethin. i've been getting 300+ around town and alot more on the hiway. and i have a gas engine with the 3.7 and a k&n. it is all stock...for now.

Key word is "STOCK",wait till you lift it and add bigger tires and some armor,bye-bye mileage.

Albert · **Posted:** Sun Jan 06, 2008 8:15 pm

tjkj2002 wrote:

jerseykj wrote:

wow i must have a special jeep or somethin. i've been getting 300+ around town and alot more on the hiway. and i have a gas engine with the 3.7 and a k&n. it is all stock...for now.

Key word is "STOCK",wait till you lift it and add bigger tires and some armor,bye-bye mileage.

that does it.....I'm gonna take all my "stuff" out of the jeep and strip it down to it's bare bones, and put a sail on top, and................

Gas mileage in the crapper...

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