On Sat, 19 Apr 2008 11:17:49 -0400, Spehro Pefhany
wrote:

Easiest thing is to reset the trip odometer every time you fill up.
Fuel consumption is miles driven since the last fillup divided by
gallons added, modulo small differences in "fullness" (or liters
divided by km driven if you want to do the metric reciprocal thing).

Exactly what I do, filled up yesterday, 19th April, unleaded.

Trip 766.7 km
Fuel 61.7 litres
Price $1.333 / litre after 4c discount, normally $1.373
Total $82.24
cost/km 10.73 cents

Fuel consumption 12.426 km / litre, 29.33 miles /us gallon or
35.09 miles per real gallon, slightly better than usual as I am not
using the aircon so much as it is cooler.
Vehicle 1994 Camry, 2.2 litre 4 cylinder. 2 x 50 km each way trips
per week, mostly freeway and about 150 km per week local short trips
of about 10 km each way.
Diesel was $1.709 / litre today at nearest fuel station, ULP $1.399

Previous fill 28th March was

Trip 732.1
Fuel 65.29 litres
Price $1.355 / litre after 4c discount, normally $1.395
Total $88.46
cost/km 12.08 cents
aircon on all time, towing trailer about 200 km, average 300 kg load.
Fuel consumption 11.213 km / litre
aircon + towing = extra fuel used