Feeling the heat? Don't believe it

Last updated 10:26 10/01/2013

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

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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.

Car Start temperature  Drive temperature  Control temperature*
Audi A6 29.5  29.5  29
BMW 328i  30.5 29.5 31
BMW M135i  29.5 29.5   30
Ford Fiesta 30  30 30
Ford Focus Trend  29  28 32
Ford Focus ST  29  29 31
FPV GT R-Spec 36 37 29 
Ford Falcon 35 31 30
Ford Territory 33 30 31
Honda Odyssey   29 28 29
Hyundai i30 29 28 30
Jeep Grand Cherokee 29  29 30
Lexus GS350 30 29  29
Mercedes-Benz C250  31 30 29
Mercedes-Benz C63 33.5 30 30
Nissan GT-R   16  17 30
Porsche Boxster 31.5   30 29
Porsche 911  31 31  30 
Renault Megane 33 29  30
Subaru BRZ 31 30 30
Toyota Corolla  30 29 30
Toyota Prius V   29 29 29
Toyota 86  31  30 30
Volkswagen CC 28 29 29
Volkswagen Golf 29 29.5 29
Volkswagen Polo 28.5 29 29

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

- Fairfax Media

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