I have a problem I don't know how to compensate for. I live in the mountains in Tennessee and get 50 to 51 mpg every tankful that I check. So what is the problem you ask. I am convinced my speedo is off reading at least 4 or 5 miles faster than I am really going. I have no guaranteed way of knowing this however it has registered the 4 or 5 faster on the police signs that show your speed when you go past. It has also been off the same speed when driving side by side with my other vehicle. I wonder what this discrepancy would equate to when figuring actual mileage?
do you have any measured mile markers on your highways? you can reset your odo and see if it matches up to the markers. tyres can affect speed and mpg read out, but the best mpg gauge is refilling and knowing actual distance travelled.
Do you have an iPhone or similar? There are free GPS speedometer apps in the app store. Speedometer+ is the one I use. If there is a true discrepancy, it doesn't necessarily mean there is also one in your odometer. Screwy, I know. It seems that there is no real penalty for having a speedometer that is off, while the lawsuits have necessitated that the odometer be pretty close to dead on.
Or you can borrow a Garmin or a TomTom from a friend and it has an accurate GPS speedometer you can compare.
If I'm going 52 km/hr (as shown on the speedo) the Garmin or Scangauge will show 50. Consistently. This is intentional on the part of auto manufacturers; it's mandated that the speedo should either be accurate or read a bit high. It encourages people to slow down.
There is a thing called a speed-o-healer that can fix your speedo to read exact. I used it on my Hayabusa which read 5 to 6 mph faster.
What I've found is that my display speedo reads just about .6 mph over my iPhone's GPS, while my Enginelink readout (via the OBDII connection) shows about 2.3 under. Weird and crazy things the auto manufacturers do.
They are designed for motorcycles but can be used on a car as well. If you read the reviews, you will see that a reviewer used it on his Honda Civic.
You have a 2010. Usually, any built-in bias works the other way unless you're rolling non-OEM tires which would make your car read slower than you're actually traveling. I'd look there first. A GPS, Police radar sign, or interstate mile markers are all excellent way of determining whether or not your car's speedo is accurate. The VSS compensator works on bikes and cars alike, and they're plug and play but I don't think I'd bother if the error is only 5MPH. Your call. Good Luck!
Nothing. The speedometer reads high, by design and legislation, to encourage drivers to go a little slower. The odometer should be reasonably accurate. (Oh hell, I answered this already, back a bit. Oh well, still stands.)
We don't have to. The speedometer by design reads faster. The odometer however is accurate. You can yahoo the variety of reasons all manufacturers do this not just Toyota.
My speedo is always reading 1mph faster than my Garmin gps. Tires are right size, new and 40lbs air. It shows 76 when my garmin shows 75
Mine is the same, even with tires now at 37 vs 40 and worn a little more. There are stretches along the interstates where they read the same and 2 mph over though, so go figure.
