I have been using one for more than 2 years. It has about 30 (I do not remember) displays only 4 could be shown at a time and each have to be different. On the XJ, the fuel pressure do not work. No out put from the PCM. The MPG reading is good but you should depend more on the intank fuel guage. When the variables are properly set, the MPG is reasonably accurate. My fill ups are within 1 gallon of what the Scanguage says it need to bring the tank to full if I do not allow the XJ to sit with the engine running for a long time.
With the 30" tires I am using, I adjust the MPH to reflect the true speed (corrected via GPS). The indash speedo is wrong. Everything else work really good. In addition you have a diagnostic tool. Check engine light is on? Use the scanguage to get the codes.
Simple to install. Plug it onto the ODB2 port and adjust the variables. Enjoy.:cheers:
