UPDATETODAY 14.08.2012 >>>>>>>>>>>>>>
History first
I used to get decent mileage but then I travelled mostly motorway miles. The best I ever achieved was one day when I had a particularly long run ( approx. 700 miles to cover in one day ) This was with me 6'3" 17 stone + a workmate at 6'7" 19 stone,work gear and a boot crammed full of work related items.
I managed 695 miles covered with 40 approx left in the tank + reserve fuel meant I could have got about 850 miles at the 52.2mpg rate had I run her dry.
Incidentally when I refuelled the DIS told me to expect a 915 mile range if I travelled in the same manner going forward.
915divided by 52.2mpg = 17.6 gallons so it all seems to work out fine!
Recently
My mpg is shot to bits, I travel a mix of city and motorway now, probably 60/40 or thereabouts, maybe even a little more city stop start than that even. The car doesn't always get up to temp and the instant mpg usually hovers around the mid 30's range, high 30's to low 40's if I'm lucky on motorway jaunts.
The average for the lifetime of the car was recently showing36.6mpg.
Based on the fact I usually get around 500 - 550 to a tank + whatever isleft in reserve it kinda works out about right.
Past week or so
As you may know I recently cleaned my EGR valve, switched to Shell V power and had a Terraclean treatment done on the car. I've been monitoring my mpg etc ever since and recently started a fuelly account to help with this. My first fuel up showed 36.7 mpg which is scarily close to the average showing on the DIS in my car.
My second fill up I looked even closer and decided to see what I could get out of her and if the steps I took had any effect. I topped her off with Shell V power and reset the instant trip, but left the lifetime trip meter as is at 36.6mpg
Over the course of the full tank I probably did a mix of 75% motorway and 25% stop start town driving. I was careful, not exactly hypermiling as the boot was still crammed full, the AC was on and the drivers window open slightly as I am a smoker.
I managed to get 750.2 miles on a full tank and this left zero miles in the DIS so I was essentially on reserves at that point.
I refuelled almost exactly the same as the last fill up at £104.01 for 70.80litres of Shell V power diesel. On the basis that my instant mpg had seen 52.2mpg but settled at 51.2mpg and the the fill up showed me that 9.2 litres (2.03 gallons ) remained in reserve, meant if I had run her dry I was looking at an 854 mile range….not bad!
This turnaround in a week or so is impressive, at least for me
From past experience the car's computer slowly builds mpg when driven sensibly and economically but reduces it drastically when the lead foot appears. 5 years of ownership has taught me once its way down at the kind of levels I mentioned earlier it takes a long time, lots of regular motorway miles and very economic driving to get the upward trend back on track
The only part I don't understand is the DIS after refuelling showed a DTE of 715 miles?
I was sure this was based on the level of fill x the instant mpg which would have meant approx. 910 mile range NOT the 715 miles as indicated.
Anyhow in the matter of less than a week my mpg isup from 36.6mpg to 42.4 according to my fuelly account, even though my instant trip on the DIS shows 51.2 and the average for the lifetime of the car is now at 37.1mpg
This shows a huge improvement for me as far as I'm concerned and I further believe that if I can continue the trend and drive enconomically I can achieve even better results.