right before i left on a thirty mile highway drive i filled the tank until it the nozzle clicked and reset the trip odometer, I went on the drive and as soon as i got off the highway i filled up again, until it clicked, when i did the calculations i got 35mpg, I know my numbers and math were right but the outcome has to be off what other factors could be in play i did 60mph and only varied it by 3mph

 

The short distance you traveled along with different gas filling conditions leaves room for ALOT of error. IMO these are the reasons for the high MPG.

 

 

How much gas did you put in after the drive?

 

Holy cow that would be awesome if it's true man

 

did you go to the same gas station and same gas pump!? even so..i kno that they click at different times...every time i fill up sometimes it clicks early and i have right under a full tank..sometimes it clicks later and it goes past the full mark.....lots of different stuff can offset the guage too...like how flat the ground is...but that would be sweet if you got that many miles per gallon man..jus puttin in my 2 cents

 

You would need to use a calibrated pump and flow rate meter on your fuel line to really find out.

I dont see any 4.0 XJ getting 35mpg! Altho it would be awesome if it could be done!!!

 

How about the simple possibility that your odometer is off because of a tire change at some point in the life of the vehicle?


35 mph just isn't possible in our trucks.


My best was 23 mpg when driving unloaded on flatter highways (no hills). That was a 97 XJ with 3.07s and 30s. (and a corrected odometer). Later, as the engine got older I switched to 3.55s and still maintained around 21.5 mpg.


My wife's matrix with a 1.7 liter motor gets 36 mpg .... to give you a reference.


Check that odometer.



Joe

 

I dont if its the same in the us, but here in SA, the pump nozzles have different pressure settings. ie. depends on how hard you squeeze the nozzle, determines how fast the petrol comes out. Now it could be that you squeezed it differently, causing a bit more turbulance this time round, thus activating the "click" earlier.
The only way I can get close to an accurate fill up on my jeep, is to painfully full it to the brim every time, making sure no more airlock etc etc.

 

If your calculations are correct,and assuming the topped off fuel level was the same after each fill up, that was one long stretch of DOWNHILL highway !!!!

 

only way to half way check for fuel milage is to keep a log of each time you fill up how many miles between fill ups and how much gas you pumped in. after about a month of doing this calculate it up and that will give you a decent real world average of what kinda milage your getting. Again as stated earlier you need to be sure your odometer is correct first

 

This is a little out there, but is it possible your trip odo was set to km/hr and not mph? My 99 XJ doesn't have that option, but maybe some did. A km is 62% of a mile. 35(.62)=21.7 which would be about right for an XJ. Just a thought.