I was regularly passed by "speeding" trucks and cars on a recent trip from Adelaide to Melbourne in my new Subaru Outback, even though I had my car set at the speed limit! I checked it with the RAA and found that I'm traveling at 10 percent below the speedometer reading i.e. doing only 92 km/h when it indicated 100 km/h. The dealer said it?s a Subaru safety feature and not change-able, but I want it adjusted so I don't have to second-guess my car's actual speed.
The speedo is allowed to read up to 10 percent higher than the real speed of your car, plus 4 km/h, and there’s nothing you can do about it. A GPS, which is more accurate, can be a useful guide to your real speed.