35mpg+ at 80mph from a fast petrol?
Discussion
JonRB said:
geeteeaye said:
That isn't what most people are doing though, more like this.
On motorway, cruising at 80mph. Notice there isn't much traffic around and decide to see what mpg car is achieving *resets trip* - ooh look, 40 mpg, isn't my car economical *catches up traffic, turns trip off and makes mental note to tell people how little fuel car uses*
That's a pretty sweeping statement. Do you have anything to base that on?On motorway, cruising at 80mph. Notice there isn't much traffic around and decide to see what mpg car is achieving *resets trip* - ooh look, 40 mpg, isn't my car economical *catches up traffic, turns trip off and makes mental note to tell people how little fuel car uses*
Or maybe they are doing a measured exact 80mph run for a considerable distance, calibrated for distance and speed, on a completely level, clear road, with no prevailing wind, same temperature, perfectly inflated tyres, same fuel, same additional weight in vehicle, everything being well maintained and serviced, same road surface, same settings inside the car (A/C etc) blah blah. Oh yes and someone in a very fast fuel tanker to refuel you on the move before and after the test (otherwise there are even more pitfalls if stopping to refuel/starting from a petrol station) to measure the amount used.
Yes I'm being silly but I really can't see an easy real-world method of accurately measuring mpg at 80mph other than entirely trusting the trip computer over a shortish distance/amount of fuel which isn't a big enough sample to get an accurate result, over a tank or even half a tank fair enough but the comparison you'll generally have is one person with cruise control, no passengers/luggage, doing 80 down a slight downhill with a following wind and an optimistic trip computer reporting 40mpg. Someone else in the same car with 4 passengers + luggage, on a hot day with A/C on, slight uphill, no cruise control but sure they're doing 80, badly maintained, low tyres etc etc doing 30mpg.
geeteeaye said:
Or maybe they are doing a measured exact 80mph run for a considerable distance, calibrated for distance and speed, on a completely level, clear road, with no prevailing wind, same temperature, perfectly inflated tyres, same fuel, same additional weight in vehicle, everything being well maintained and serviced, same road surface, same settings inside the car (A/C etc) blah blah. Oh yes and someone in a very fast fuel tanker to refuel you on the move before and after the test (otherwise there are even more pitfalls if stopping to refuel/starting from a petrol station) to measure the amount used.
Yes I'm being silly but I really can't see an easy real-world method of accurately measuring mpg at 80mph other than entirely trusting the trip computer over a shortish distance/amount of fuel which isn't a big enough sample to get an accurate result, over a tank or even half a tank fair enough but the comparison you'll generally have is one person with cruise control, no passengers/luggage, doing 80 down a slight downhill with a following wind and an optimistic trip computer reporting 40mpg. Someone else in the same car with 4 passengers + luggage, on a hot day with A/C on, slight uphill, no cruise control but sure they're doing 80, badly maintained, low tyres etc etc doing 30mpg.
Somehow I don't think the OP was asking for a Mythbusters-style scientifically diligent and reproducibly accurate test regime, but rather a ballpack idea based on the experiences of owners of various cars. Which is what people are giving him. Yes I'm being silly but I really can't see an easy real-world method of accurately measuring mpg at 80mph other than entirely trusting the trip computer over a shortish distance/amount of fuel which isn't a big enough sample to get an accurate result, over a tank or even half a tank fair enough but the comparison you'll generally have is one person with cruise control, no passengers/luggage, doing 80 down a slight downhill with a following wind and an optimistic trip computer reporting 40mpg. Someone else in the same car with 4 passengers + luggage, on a hot day with A/C on, slight uphill, no cruise control but sure they're doing 80, badly maintained, low tyres etc etc doing 30mpg.
What exactly is your problem here?
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