Just drove from So Cal to Arizona, and started with a full tank of course. Total miles were about 325, give or take a few miles. The average MPH on the display read 72 with an average MPG at about 47 upon my arrival to my destination. I figure the actual MPG would be around 43 or 44, but how accurate is the MPH since the actual MPG if off to begin with (calculated to what's on the display). During the drive, I varied between 75MPH to 85MPH. Thanks
That is a bit difficult to check how accurate that is, but you could get a scan gauge as a supplementary tool as they tend to be a lot more accurate. I find that the MPG my car tells me I am at is usually at least 2 MPG off. So, MPH can't be much different I am sure. But, again, there are many people on here and other hybrid forums that rely on a scan gauge to get much more accurate readings overall.
The speedometer is off by approx. 1.5mph +-.5. It is of by design. The Odometer, however, is very accurate. The car's ECU ears the correct speed. It is only the display you see that is off. The only effect this has on your fuel economy is that you generally drive 1-2mph slower than the speedo is telling you.
I agree, when going by a radar speed trailer where the local police usually deploy along the roadway to advise drivers of their speed our Prius is off by about 1 to 1.5 mph more than the radar trailer reads...
