best way to get best MPG?

[stevelock]

What would the best way to get the best mpg from my 96XJ and 97 ZJ. (Not driving is not a option for me.) both of my jeeps are stock and daily drivers.

[Ace$nyper]

keep away from gas pedal 4Ls suck gas
tune up change all filters oil air etc
check tire pressure upgrade intake and exhaust more power + better mpg.

join in the club of biting the bullet. can't really get good milage with XJs

[JohnnyWooWoo]

Try taking out the front driveshaft.I've heard,but not tried,that this works.Upgrade your plug wires,go to a K&N air filter.These I've tried and am happy with the results.

[JDPascal]

1. New plugs, correctly gapped along with good wires and dist. cap.

2. Set cold tire pressures to 2-3 psi above the vehicle recommendation but do not exceed the maximum pressure on the tire side wall.

3. Practice fuel efficient driving techniques.
Put a penny on the dash or center consul and drive with the objective of keeping the penny from sliding around. You will find that you will be slowing down sooner with out the help of the brakes and accelerating more smoothly and easily and timing your approach to stop lites to avoid having to come to a complete stop before the lite turns green. Another way of looking at it is to drive like you have a raw egg glued to the gas pedal and another to the brake pedal then you have to drive so you don't break either egg.

These people that hurry by me and then I coast up behind them as they wait at the next stop lite are wasting their money on gas and need to learn to relax.....They are way to tense when they drive like that.

JD

[ec437]

The best way to drive for fuel economy is to accelerate at about 80% throttle and then mantain a constant speed once you get up to speed. Try to avoid having to use the brakes. Always keep the RPMs pretty low except for when you are engine braking.

[sector95]

Man it's deja-vu all over again.... JD, I hadn't heard the "egg" trick since the oil embargo... kinda brings back memories.... Next thing will be JC Whitney selling "Mileage Meters" (essentially just vacuum gauges)

Another little "mileage master" technique is to let off, ever so slightly, on the gas pedal once you reach cruising speed. You can pull back on the go pedal a hair and still maintain speed.

Be smooth.... keep a steady speed... and anticipate lights and traffic. The less flapping of the gas pedal the more mileage you'll get.

mike

[thinmints]

]

first off if you are driving an XJ medicore gas mileage is something that you will have to live with they were not built for good gas mileage, my 96 gets 18 around town and just over 21 on the highway so im happy with what i get although now with gas here in KC running $3.00 its about $60 bones to fill her up.. ive thought about getting a RICE burner but i will keep her until she falls apart proper tire inflation, filter change and good set of plugs should keep you around the 18+ mark also that air spinner thing that you can put in your airfilter works well on the XJ, more pep and better MPG hope this helps

[sector95]

If you have the an automatic transmission, learn to make it shift with the gas pedal. Once you begin accelerating, especially from a stop, you can control how soon the tranny grabs the next gear (within reason) by just easing up slightly on the gas pedal.... it doesn't take much. This technique takes a little practice and you have to be smooth. Also, take note of the speed where the transmission converter locks up; on my XJ it happens at 42MPH. The goal here is to get the transmission into lock up as quickly as possible and keep it there. For the Aisin-Warner 4spd auto in my '00 XJ, it won't lock up until the speed exceeds 42 mph... but once locked, I can slow to at least 35mph and the tranny will stay locked.

Of course the bottom line, as you might've already figured, is these vehicles are not "mileage champs"...... 17-18mpg is probably the best in-town mileage with 20 -21mpg on the highway. Keep it tuned, keep the tires inflated at least to the proper psi (a couple of lbs extra as suggested is good) and be aggressively attentive to being smooth and anticipating stops.


mike

[fredjacksonsan]

Originally Posted by ec437

The best way to drive for fuel economy is to accelerate at about 80% throttle and then mantain a constant speed once you get up to speed. Try to avoid having to use the brakes. Always keep the RPMs pretty low except for when you are engine braking.

80% You could probably get away with 10% throttle and do just fine.

[neon_rt]

Another good tip is to coast as much as you can. When you let up off the thottle, the Injectors are turned off until the RPM drops to about 1200 RPM (except when cold or the A/C is on). When going down hill, instead of giving it gas to maintain 60mpg, you can let off completely if the hill is steep enough to keep you moving at an acceptable speed (55 or so). Unfortunately Jeep don't coast all that well because of the Brick like shape.

[sector95]

I'm not sure fuel flow to the injectors is shut off completely in the 4.0L..... I have a GMC Sierra with a 5.0L V-8 and you can feel it when the fuel flow is shut off during extended coasting.... you can feel the engine braking effect as if you downshifted. I don't notice that with the 4.0L.....

mike

[Saudade]

OK, I'm going to need to see some reference that says the fuel flow is shut off under these circumstances. This means the engine is off with no power to the brakes or steering.

If I press the gas pedal before the rpms drop to 1200, what's supposed to happen?

[sector95]

Yeah, now that you bring it up, that would be kind of hard to believe the fuel flow would completely shut off. I think what happens with my GMC is when the transmission computer senses an extended "coasting" condition (the drive output is overrunning the engine input) the fuel flow is dropped to something below what would be required for normal idle.... it is never shut off completely. But there is a definite feel of engine braking going on.

With my XJ, I don't notice the engine braking when I have an extended period of coasting..... I don't think the transmission and engine control computers are that sophisticated on the Jeep....

mike

[JDPascal]

The sensation of engine braking when the vehicle is equiped with an automatic transmission is due to the way the gears are achieved with the planetary gear sets useing the different clutches rather than just shutting off the fuel to the cylinders.

If you slow down when the transmission is in drive, you notice very little engine braking as the transmission shifts down thru 2nd and 1st to a stop. If you manually select 2nd or first at compariable speeds, you will find that engine braking is more noticable because the shafts and gear sets are held in a different way when the gears are manually selected. (especially in first gear.)

When in over drive you have zip for engine braking because of the inversion of the mechanical advantage in the gear ratios.

Allowing the throttle to close completely while the speed/weight of the vehicle is driving the engine is a good way to increase oil consumption (especially in older worn engines) with high vacuum trying to draw oil past the valve seals and rings.

Hope this wasn't too far off the topic but it seemed related to the direction of the last few posts.

JD

[Saudade]

Thanks JD.

Compression braking is most useful on a standard trans vehicle due to the "hard" connection of the rear wheels to the engine. With my auto, I've dropped the selector down into 3 to help control speed on long downhills, and even 1-2 when I needed the extra "anchor".