I usually fill my car up from empty to full every fortnight from the same service station and I pretty much take the same route for the fortnight (to and from work). So you would think that my fuel consumption would be averaging the same week in week out.
Two weeks ago before I changed the fuel filter the Av. fuel con. was between 12.2 and 12.6 Litres. Since I've changed the filter this has gone down to 10.2 to 10.6 Litres, awesome very happy with that. But the wierd thing is this: the second time I fill up my car since the new filter the Av. fuel con. shot up to 13.4 Litres.
The observation that I made was that just after filling up and reseting the trip computer I drove a little bit harder than usual and the Av. was hoovering around 13.6L. I didn't think much of it because the first couple of Kms the Av. jumps around a bit anyway, and I was driving a little harder (as mentioned before).
I thought the Av. was going to go back down to about 10.2 - 10.6 after I start driving normally again, but it didn't and I could notice that I wasn't getting as many Kms out of the fuel used (about 50kms less per quarter of a tank).
Now...I seriously doubt that the trip computer and the engine managment are connected apart from the fuel readings it shows but after I reset the trip computer, the Av. for the second half of the tank went back down to 10.2 - 10.6 and I am driving the same as I was before except for the 2-3 kms of throttle happy driving.

Is there any chance that when reseting the trip computer the ECU adjusts to your driving in the first few kms?
Could this be why my Av. fuel con. is high (13.3L) if I drive a bit hard for the first few kms and why the Av. is low (10.2L) if I take it easy for the first few kms?

WHY OH WHY?



(I realise this is a long a complicated explenation and I apologize in advance.)

Where are all the techheads?

I cant see the trip computer changing the fuel consumption, i think it's just all in ur head :P.

Could be............... :confused:

I recently changed from BP 91 octane to BP optimax 98 octane in the hope of getting slightly better fuel consumption, quieter idle and better response. Not to mention hopefully it'd do as claimed as clean my engine :D though I don't see that happening.

Anyway, I reset my trip meters. It used to say about 14.5+L/100km, now it's saying about 13.5+L/100km. I guess this is a slight increase and over a tank would even out with the extra 10c per Litre I pay for optimax, not to mention with the added responsiveness.

Though I'm still unsure why my readings are so high, which is kind of annoying. Specially since it's only the 3.0L TJ, not the 3.5L. However, I've been told by a friend it's because my 3.0L has to work harder to pull the cars weight, thus consuming more fuel then the 3.5L which would pull it with alot less strugle. (Specially up hills etc, where the engine really has to work)

In regards to your post though, I've also noticed my trip meter reading funny in regards to the estimate of L/100km. Like the first 50km I drove it was giving 15+L/100km, I reset it and now it's giving 13.5L/100km. I didn't think I was driving any different either.

On a side note, does cleaning your fuel injectors help in regards to performance and fuel consumption. Also is it worth it (I heard you had to crack the head to clean them?) My car has done 140,000km now so I'm guessing that could be why (dirty fuel injectors) I have such high fuel consumption.