Fuel quantity monitoring

[Dogfuzz]

I like the addition of the guage giving approximate mileage remaining as well as a regular quantity guage. However I'm finding the former a wee bit unreliable.
I filled up recently ( to full)-and mileage monitor read 440 miles remaining --which is about average.
I then drove 10 rural miles and the following morning the guage displayed 398 miles remaining. Wonder what's going on?

[Percy247]

I also find that both the fuel gauge and estimated range do act rather strangely at times. Our range goes down very slowly at first then faster nearer empty. I have seen the range increase on occasions.

I guess it uses your current average mpg and multiplies this by the estimated fuel left in the tank to give an estimated range.

Over time the float mechanism and the variable resistor may get worn, so that the digital guage on the dash does not fall in a linear way.

I only measure my actual fuel economy every time I fill up and ignore anything the car tells me.

[HouseSpider]

I've changed jobs recently & now only travel 3 miles to work a day. Fuel consumption & range took a hammering.
However I did a 100 miles (mainly motorway) drive last Friday. The remaining range on starting the journey was 254 miles. At my destination the range had dropped to 249 miles.
This was a good example of how all the different factors of a journey can dramatically alter the fuel consumption.

[SeeXthree]

That estimate is always based on optimum economy driving (ie. constant low throttle input 1500-2000 rpm). I drive at least 70 miles a day between city and motorway and several 300 mile daily round trips. I’ll often drive with the fuel economy monitor on and it varies between 80mpg+ when coasting with or without gear engaged, 60mpg-ish at 56-64mph and 2000rpm, 45mpg at 2400rpm and 68-73mph.
On the other side of the coin I can quite easily get that figure down to about 5-10mpg if I’m errrr.. in a rush.
I always use the same premium fuel and 3000 mile oil changes in my vehicles (again, premium recommended spec not dealer bulk rubbish)

[TEB]

Generally get a range indication after filling up of between 320 and 340 miles, as I mainly drive on winding rural roads with a few steep hill climbs.

Occasionally I do take a long motorway journey, with today being one of these. I filled up shortly after setting off, and from memory the range was around 335 miles. I drove close to 160 miles to collect a winter set of alloys for my wifes car, then returned home, so around 320 miles. Filled the car up again close to home and the range was showing 73 miles. After filling up with 32.17 litres, the range was showing 380 miles. This is consistent with previous motorway trips, were the range indication noticeably jumps up, compared to my normal trips to work.

If I've got my sums right, I think I got an average of 45mpg today, which seems quite remarkable for a 2ltr petrol 4x4 fitted with all season tyres, travelling at national speed limits, and with an extra set of wheels onboard for half the journey.