Feeling the heat? Don't believe it

FPV GT R-Spec's thermometer was seven degrees off during Drive's testing.
FPV GT R-Spec's thermometer was seven degrees off during Drive's testing.

If your car is telling you it's 50 degrees outside don't believe it. 

Car thermometers can be inaccurate by 15 degrees or more – something likely to gain more attention in the current warm summer conditions. 

A Drive test has shown that the digital external thermometers now standard on most new cars can vary wildly between vehicles, with readings on a 30-degree day varying between 16 and 37 degrees.

The exclusive test took dozens of temperature readings from 27 cars during testing for the 2012 Drive Australia Car of the Year awards

Data was taken from the cars over two hours, with a Mazda CX-5 revisited every 15 minutes as a control reading.

We measured temperatures with the cars parked in the Wakefield Park NSW pit lane, and took each for a leisurely lap of the circuit at 60km/h to see if that raised or lowered the temperature.

Some results dropped a few degrees after the 2.2km drive, while others rose slightly .

More than 60 readings over two hours resulted in an average temperature for the field of 29.2 degrees, a little lower than the control-car average of 29.8 degrees.

The temperatures were spread between 16 and 37 degrees, with some of the more expensive high-performance cars returning the most variable readings.

The colour of the individual models also appeared to play a part: the hottest and coldest cars were painted black and white respectively.

The highest temperature reading came from a black FPV GT R-Spec, which told us it was 37 degrees outside, when other cars suggested the true temperature was closer to 30 degrees.

A few vehicles reported the temperature at less than 30 degrees, but only one reported a temperature of less than 28 degrees.

The pearl-white Nissan GT-R – a $170,000 sports car – was alone in its opinion that the mercury should read no higher than 16 degrees, not long after the FPV reported an ambient temperature of 36 degrees.

A second check of the GT-R saw the big Nissan's temperature rise to 17 degrees.

Thermometers seem to offer only an indication of the temperature: you should probably take them with a grain of salt.

Especially if you drive a Nissan GT-R.

CarStart temperature Drive temperature Control temperature*
Audi A629.5 29.5 29
BMW 328i 30.529.531
BMW M135i 29.529.5  30
Ford Fiesta30 3030
Ford Focus Trend 29 2832
Ford Focus ST 29 2931
FPV GT R-Spec363729 
Ford Falcon353130
Ford Territory333031
Honda Odyssey  292829
Hyundai i30292830
Jeep Grand Cherokee29 2930
Lexus GS3503029 29
Mercedes-Benz C250 313029
Mercedes-Benz C6333.53030
Nissan GT-R  16 1730
Porsche Boxster31.5  3029
Porsche 911 3131 30 
Renault Megane3329 30
Subaru BRZ313030
Toyota Corolla 302930
Toyota Prius V  292929
Toyota 86 31 3030
Volkswagen CC282929
Volkswagen Golf2929.529
Volkswagen Polo28.52929

* Control temperatures were taken every 15 minutes from a Mazda CX-5.

Fairfax Media