I've only recently discovered my odometer isn't entirely accurate. There must be a couple of teeth missing off one of the cogs in the speedo or something, as it's not ticking over all the time, which is a worry as I do my oil changes according to the speedo reading. I've had it fixed but also bought a motominder hour meter as a backup. I normally change my oil every 500kms. What does this equate to roughly in running hours?