Have a 2000xj, 4.0l engine 231 tcase. I added a overhead console because i found one in the junkyard and i like the information they give. I know that the numbers aren't going to be perfect with bigger tires, but in the city i get anywhere from 18-22 depending on speed. On the expressway going 70, i get 12-14mpg. I know aerodynamics play a part in this, but most people usually get a few more mpg on the highway instead of less.

I have new plugs, and seafoamed the engine recently. the only thing i can think of is the precat o2 sensor?

any idea or do you think its the o2 sensor?

 

That things way off.Most people i know get 15 to 18 highway. and 10 to 15 city.I have never heard of anyone getting as much as 22 city.

 

are you just going by the junkyard mpg gauge or you actually filled up your tank, drove in the city for 50-60 miles and then put more gas and measured the mileage, and then did the same on the highway. because frankly, 18-22 is more like a city gas mileage for a medium size car.

 

my "city" miles arent really stop and go like most would think. its pretty much a constant 45-50mph. I know that isnt city driving for some.

Either way, i dont think the console should read less on the expressway. I do know it seemed to suck up a bunch more gas before the school semester ended traveling about 14 miles from home and back i burned a bit less than a 1/8 of a tank.

edit: Tural, im strictly going on what the console is saying (i know its off). I calculated the mpg in my head the first few tanks but i know it sucks up a lot more gas on the expressway compared to normal city driving going the same distance.

 

50-55mph. is going to give you your best gas milage anything above 60mph is going to increase your fuel consumption. At 70 I'm getting around 10-12mpg. Stop and go with a 7 mile sprint at 55-60mph. 15-17mpg.

 

alright timber wolf, i know what you mean about the 55-60mph being the best, just wasnt sure how reliable the change in the console was from a 5-10 mph gain. ill just keep it a bit under the speed limit

 

X2. exactly what he said. and i'll add to it that if you're driving 45 in town without stopping for red lights you can easily get 22 mpg. i do. because, you're mentally in a slow traffic, so you go easy on the "GO" pedal. but that's not what is meant by city mpg.
city mpg means 25 mph and red light every block.
so, it's actually normal that you're getting 22mpg driving at 45mph and 10mpg driving at 75mph.

 

yea, theres nowhere that the speed limit is 25 here besides in neighborhoods haha. i figured my highway was a lot lower than usual though as i seen people here saying they got 16 highway, but didnt take in consideration that a lot of states the highway speed limit is 60 instead of 70.