No vehicle's speedos is entirely accurate. Has something to do with 'Pi'. 22/7 & all that. Someone way smarter than me tried to explain it to me one time. Anyways...the manufacturers are aware, (as are the cops!) so they ere to the slow side on the speedo.
I'll bet ya that any vehicle you try your GPS in, they will all be just a bit s l o w e r, for the speedo against the GPS. This would all be on a vehicle that has not had a gear or tire size change. Stock trim. A 'safety' feature?
But there is also a few variables, too. Something as small as a couple of lbs. in tire pressure difference in one or all four tires, will change how your speedo reads. More air, taller tire, less rotations per mile. But better mileage.
As far as the cops go, (if that's what you're worried about) from the ones I've known, they have said that their tolerance is 90/10. If the speed limit is 60mph, & 90% of the traffic is doing 70-75ish, no-one's getting pulled over. Or, if the traffic is light, doing around the limit, anyone going 10%+ is getting lit up. Could be a quota thing too.
If it's not out too much, I wouldn't worry about it. I rely on my GPS.
