MPG

[Lib88888]

Hi guys! My trip computer says I’m getting 41mpg on decent journeys and around 32mpg on short journeys.

However, the fuel needle doesn’t reflect this and seems to go down pretty fast.
Would there be a reason the mpg is saying different to what it actually is?
I’ve tried resetting it also.

Thank you

 

[nbas]

Have you changed the tire size?
If you did, you need to Recalibrate the Speedometer

 

[Lib88888]

May I ask how you Reset the trip computer?

 

[nbas]

On the EVIC overhead console there is a RESET button. If you press it while showing MPG, it is reset...

 

[Erskine]

What country are you in and what engine?
I've managed 52 mpg on a run with 2.8 CRD and proper job British Empire sized gallon (20% more fun but about 10x more expensive).

 

[Lib88888]

Uk! I’ve replaced all serviceable items. But it appears to have dwindled down slowly, maybe the recent hot weather? Currently getting around 30mpg indicated on the trip computer

 

[Erskine]

Uk! I’ve replaced all serviceable items. But it appears to have dwindled down slowly, maybe the recent hot weather? Currently getting around 30mpg indicated on the trip computer

The VM engine likes it hot so doubt it is the weather. Have you tried cleaning the MAF sensor (on the intake just after the airbox). If you VERY GENTLY clean the elements with a soft artists paint brush and then lightly spray it with electrical contact cleaner (not brake cleaner) let it dry then refit. Failing that I suppose get it hooked up to a laptop by someone who knows what they are looking at and see if anything is amiss. Normally if it's injectors it will be idling rough AF. Hopefully another member will be along shortly with words of wisdom!

 

[KJowner]

Slow loss of power and mpg is quite likely to be worn old injectors not spraying like they used to, but it could also be a dragging brake, blocked air filter, worn cam, stretched cam belt, low tyre pressures or dirty / failing MAP as Erskine says, without going over it or knowing some service history it's a hard one to call.
However a genuine 30mpg is reasonable for a 2 ton, 2.8 housebrick in mixed driving. I wouldn't rely on the fuel computer, measure it manually between brimmed tankfulls.
My manual was better on fuel than the auto but auto is much nicer to drive, the fuel computer says around 25~26mpg but it's reading US mpg so 28~30 ish, it will do a bit more on a long run and a bit less towing.

 

[Lib88888]

Awesome, thank you both !!!

 

[KJowner]

This might help, not my handiwork, I pinched it from Lost Jeeps! Depending on the age of your Jeep you might not have all the things in the photo, the US Jeeps were all later spec.
Of all the items pointed out below the most critical for fuel and performance is the MAP, our old Jeeps don't have any feedback from lambder so the fuel injection is adjusted by throttle position and the MAP sensor that looks at boost pressure and temperature.

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[KJowner]

Just returned from a trip dragging my caravan, I dropped some injector cleaner in and cleaned the MAP sensor before we set off, only a light misting of oil on it. Got home, Zeroed the fuel computer and went for a 30 mile round trip to pick up 500kg of coal, so empty on the way there and heavy on the return, just rolling along at traffic speed on smaller roads 40~60 MPH, when I got home the computer was showing 7.8 Lts/100KM, 30 US MPG or 36.2 UK MPG.
Not too bad for a 20 year old truck.