About time you guys caught up
These has been getting more common over the past few years this side of the Atlantic. They are not usually fitted as a separate gauge or readout but as part of a trip computer. My Fiat Bravo has this fitted and it can tell me not only my insantaneous fuel consumption, but also the average since the trip mileage was last reset, my average speed since the trip was reset and my range on the fuel in the tank, It also has a second milage trip and will work out average speed and consumption since that was last reset too. Since I reset the first trip every time I fill up I can tell how I am doing since that fill and I can tell how I'm doing since I got the car 6 months ago. And having those does make a difference. I do drive differently now because of them, doing my best to keep the consumption above 50mpg (imperial gallos - its also a diesel car). The worst average I've had is 42mpg around town, which meant the tankful only lasted about 450 miles. The best is 59mpg on the motorway at a constant 60mph. My 'most average' average is around 48mpg, which gives me about 520 miles on a tank. I have done a little experimenting, driving for a short time as I used to (lost about 3-5mpg) and also trying to find out if going too slow in a high gear uses more fuel than a slightly lower one. So far results are inconclusive as the difference is very small and road conditions seem to play a big part, but my gut feeling is that the high gears work down to about 1200rpm on the level (this diesel engine has a rev range of 800-5000rpm). Below that the engine is OK, but its seems to use a tiny bit more fuel. Also, hills or anything that need acceleration means dropping a gear (or two), so these very low revs are only practical if I know I'm going to be running at a low constant speed. Now, if I didn't have the trip computer I would never have tried running with the engine much below 1800-2000rpm, which is about 2 gears lower and nearly 5 mpg worse at 30mph!