Speedo Vs Average Speed

[motowpk]

Comparing the speedometer indication to roadside radar speed displays indicated the speedo reads high - not unusual in many vehicles. On a recent trip with many opporunities to maintain a constant speed I compared the speedometer read out to the average speed indicated on the information display on several occasions. Consistenly the speedometer read higher than the information display average speed. For example, at 74 mph on the speedomoter the info display average speed is 70 mph.

This makes me wonder if the average speed on the information display is from the NAV system and thus GPS based providing a more accurate indication than the speedometer and thus provides a correction factor to one's speedomeoter.

Comments? Thoughts?

[pauljcl]

Comparing the speedometer indication to roadside radar speed displays indicated the speedo reads high - not unusual in many vehicles. On a recent trip with many opporunities to maintain a constant speed I compared the speedometer read out to the average speed indicated on the information display on several occasions. Consistenly the speedometer read higher than the information display average speed. For example, at 74 mph on the speedomoter the info display average speed is 70 mph.

This makes me wonder if the average speed on the information display is from the NAV system and thus GPS based providing a more accurate indication than the speedometer and thus provides a correction factor to one's speedomeoter.

Comments? Thoughts?

My speedometer reads 2-3mph fast at all speeds (in excess of 60mph to 100mph), checking against a GPS. I don't have the Lexus NAV, but a 'portable' Garmin.

[1990LS400]

Even in my old non-nav 00 LS400, the average speed shown in the trip computer is much more accurate that the high reading of the speedometer. My guess is that the speedometer in our cars is purposefully set to read a little higher that the true speed.