yep good point some facts ive looked up from studies
Temperature Compensation of Liquid Fuels
Typically, in the region of ambient temperatures, petrols will expand or contract by 0.12% volume for each ºC change in temperature while diesel fuels will change somewhat less, 0.08% volume/ºC. Thus relatively small changes in temperature will result in significant changes in volume; 2ºC will result in 0.25% volume change for a typical petrol and 8ºC will result in a 1% change, while the same temperature changes will affect diesel volumes by 0.16% and 0.6% respectively.
The fuel temperature definitions given below have been derived for use through the report. These have previously no industry acceptance but were defined to allow expression in a objective way of temperature regions around the standard temperature of 15 °C.
Hot fuel > 24°C Approx. 0.6% volume difference from 15°C
Warm fuel > 17°C Approx. 0.16% volume difference from 15°C
Cool fuel < 13°C Approx. 0.16% volume difference from 15°C
Cold fuel < 6°C Approx. 0.6% volume difference from 15°C
modded the chart to show diesel figures
the tanks are underground so ambient temp is less of a factor on underground fuel temp?
so it is probably best to fill up on a cold morning after maximum cooling overnight.
probably not best to fill up on a hot afternoon after maximum heating all day.
but say you filled up 60l on a hot day and then weather turned cooler to cold the tank would now hold 59.28l.
say avg 45mpg 0.72l loss equates to around 7miles lost or gained if other way round
its there but how much it affect mpg results hard to say, but yeah log temp at time of fuelling also .
Last edited by sussexa; 09-06-15 at 08:06.