After Steve Wightman noticed other vehicles whizzing past him on the highway as he drove at what he thought was the speed limit, he decided to investigate further.

So the Belleville, Ont. man took his 2016 Mitsubishi Outlander on the highway again, along with a GPS device to compare its speed reading to his speedometer.

“My speedometer was saying 110 (km/h) but my GPS was saying 102 (km/h),” he said.

Wightman even enlisted the help of a police officer.

“I was doing 80 (km/h) and the policeman said I was doing 73 (km/h),” Wightman said.

Wightman says, in his testing, his SUV generally showed a speed four to five kilometres an hour faster than his GPS.

The disparity was even greater at higher speeds – the speedometer once told him he was doing 120 km/h when the GPS said he was only driving 113 km/h.

When Wightman took his vehicle to Mitsubishi, he was told that the speedometer’s performance was within industry specifications.

“His variance falls within the acceptable industry standard of between two per cent and eight per cent (plus or minus) of the actual speed,” a Mitsubishi spokesperson told CTV Toronto on Monday. “This is an industry issue and not about one car company or another.”

Speedometers typically rely on sensors in a vehicle’s transmission to measure how fast the wheels are spinning.

That means, if the original diameter of the tires changes due to regular wear, improper inflation or replacement, for example, the speedometer will no longer be accurate.

In Canada, Transport Canada doesn’t have any regulations on speedometer accuracy.

Nevertheless, Wightman believes the company should repair his SUV’s speedometer.

“I would like to have a new vehicle or have them fix it,” he said.

With a report from CTV Toronto’s Pat Foran