2000 xj 2.5 inch lift,30 inch tires.Ford 3.8 liter ev6 injectors banks header.free flow exhaust.Snythetic fluids all.Mpg's hwy mid 20's city last fill up 17-18. I used a superchips tuner to fix the speedo I think it worked (for the 30 inch tires but it didn't really show much of a differance).

 

I don't think that is true.Here's a true fact as soon as you lift any car truck jeep etc. You loose a big chunk of your gas mileage.

 

That may have been the case with a cold engine with a carb, but with EFI, it is not. Imagine dumping 10 minutes worth of fuel into your engine in a sew seconds. It probably would not start since it was too rich.

I work in a product development department for a large suplier of gasoline and diesel fuel injection components. We are always working to get more miles and less polution out of every gallon of gas. One method comming is the use of start-stop technology which will stop the engine at a light and restart it as soon as it senses your foot coming off the brake. I am just employing this technology manualy. Sometimes I shut down when I am rolling up to the light. I keep constant pressure on the brake to avoid losing booster vacuum and the (manual) transmission in gear in case I need to restart. If the light changes early, dump clutch and go.

 

96 SE 4 door 4x4 stock. drop in performance air filter. only getting 13.5 mpg mostly city driving. 123xxx on the clock.

 

wow that seems a little excessive. I use to do shut off my car back in HS to see how far i could coast and try to say fuel but ive never noticed a difference in gas mileage. When you downshift the motor doesn't use any fuel, it basically becomes a vacuum pump until rpms get too low or you step on the gas pedal does fuel actually get dumped into the motor.

 

1993 2dr all original, i'm only getting 10 mpg... and thought that was good. vehicles at work (we had two xj's, now only one) get about 8.5 mpg. one reason one was gotten rid of and other will be soon. will have to figure out why i'm getting so bad. My entire drive to work is city and only 10 minutes, motor does not even get to temp before i get there. soon as i get on to high way she goes up to about 18 mpg.

 

Cold engines are way less efficient than hot engines, and city traffic really sucks for big engines like a 4.0L. If your in a huge city with low quality air that also comes into play. Best you could do is have a clean air filter and lay off the A/C on hot days... that's just my idea though :P

 

HA ha ya that does seem a little excessive, but to each is own! At least there's people out there actually actively trying to save our planet (or get better MPG but both come hand in hand lol). I think for EFI engines it doesn't matter too much about start up and idling, I once played hockey on a pond for maybe an hour or an hour and a half after dark, someone started up their subaru and let it idle with the lights on for us. Gas gauge didn't move off of the full line! Anyone heard of the "turn off half the cylinders on the highway" thing? I wonder how that compares to start stop tech. When you do your manual start stop thing consistently for a whole tank, what kind of mileage do you get?

 

has anyone considered the extra wear and tear on your starter and battery if that little bit of fuel is gonna break the bank then get a prius

 

Fuel is still being sprayed into your engine as long as the motor is turning and the ignition is on (higher RPM = more fuel). If it did not, your motor would shut off. I do not downshift, I coast as much as possible. No sense in racing to the light, stomping the brakes, and then having to race off to the next light. I roll through most lights in third gear.

I only have to use the starter about one out of five shut downs. Forget a Prius; it cost more than it saves. Paid $750 for the Cherokee and put some more $ into it. I used to to a Catalina 22 to the ocean and back once a month and used it last month to tow my 72 Chevelle and my wife's 66 Stang to our new house (one at a time). Try that with a Prius.

 

? if there was fuel being sprayed into you motor then you wouldnt be able to down shift to slow down and i can slow down pretty darn fast without using my brakes. For someone being conscience about fuel mileage I'm kinda shock you dont down shift, its the best thing about manual vehicles. next time you turn off you jeep while coasting leave it in gear while you turn it off and keep your foot on the gas pedal alittle bit, the weight of the jeep will keep the motor spinning but you will slow down

I down shift to slow down for stopping or making a turn, most of the time when i catch it soon enough i dont need brakes to stop at light (hills or mountains depending) , or i slow down just enough that i dont have to stop for traffic.

what kind of mileage you get doing this coasting and restarting business? I average 18-19 every tank (mixed city and hwy, mostly cityish type driving) and i dont drive like a grandma, I like to make my locker chirp and i do get to 75 with a hurry on the hwy with 3.5" lift, 3.55 gears.

edit: when this jeep was 2wd i would average 21-23mpg but after winter was over i fixed the whole 2wd problem

 

Sorry for the hyjack on the thread, but the question was asked, and maybe this will clear some misconceptions.

You will still slow down even if the fuel injectors are spraying fuel. The amount of fuel they spray is adjusted by the:

MAP sensor: less vacuum (or more boost) = more fuel. When you close the throttle, you create more vacuum and require less fuel

Engine RPM: higher RPM = more fuel (more air being pumped)

Manifold Air Temp: Colder air = more fuel (to maintain Stochiometric A/F ratio)

Engine Temp: Cold engine = more fuel

O2 sensor: Used to fine tune the A/F ratio depending on what is hapening with the other items above.

Throttle position sensor: throttle opening = more fuel (like an accelerator pump on a carb). Some systems (IDK about Jeeps) have a flood clear mode which cuts back the fuel if the throttle is opened up with the engine trying to start.

I average 16.4 MPG overall. When I take longer trips (~400 miles or more), I will get around 19 MPG. Stitch (my Jeep with 232k miles) certainly could do better on gas. My Chevelle gets 12.5 after switching to tuned port injection. It was 8-10 MPG with the carb. My $500 Mazda MX6 gets 32 MPG.

 

Did you just tell him to leave it in gear and shut the jeep off and coast? That'll give you whiplash! not to mention then your breaks and steering will be manual, that's not a good idea to do all the time, it'll also be pretty hard if you're not very muscular to break and steer. You'll end up breaking your power steering or breaking the car in front of you if you can't stop fast enough. That's just..... not advisable at all. And keeping down the gas pedal a little bit will do nothing if the engine is off?

anyway, you don't have to buy an expensive prius to save gas money, there are actually cars that get better gas mileage than the prius, that just run on gas. I've personally seen a honda civic and a saturn ion get better than 50 MPG. I just hate it how everyone related gas mileage to freaking prius.

 

Well..I drive my Cherokee to work...40 miles round trip...92..5 speed ..posted specs...21-23 this week...two looong trips ...25/26...a little lower than the 27.5 ...it got at 60-65 the past year ..but I noticed that the mileage at 55 mph and 65 is spot on the same ..same route and distance..speed ..everything the same...and above this ..like 70-75 ..21-22mpg...I have checked this over 20 times this year....I am driving a brick..for MPG...and it is not too bad.

 

88 limited, auto, 4 wheel, 235/75r15 AT's, just filled up my tank for the second time and got my first number.. looks like about 16.5 mix city, little highway, 22 mile one way commute to work.