Is your P30 Speedometer accurate?

[cncsparky]

I noticed on my trip last weekend that my speedometer reads a solid 5mph slow at highway speeds, compared to my Garmin GPS.  Has anyone noticed the same?  Was running what I thought was 60 but then noticed the GPS said 65.  For fuel mileage concerns I'd like to keep at 60 or 55. 

[DonD]

My speedo is slow, the odo is ok. I drive by tach and GPS.

[ramit]

mines shows slow to by 10 kph but also have oversized tires on it

[cncsparky]

I assumed the tires are factory size.  8R19.5  ??

[DonD]

My tires are 235/85/16, factory are 7.50-16.

[Rickf1985]

Mine is off by about 7 MPH. Shows 67 at 60 GPS. That explains my dismal mileage on the first trip. I will slow down for the next trip. Stock tires.

[ramit]

i believe my tires ar 255/80/16