So my speedo has been off because of tire change and DIC showed around 13.5 on mpg. Yes did it by hand also and it was in a couple of tenths. Changed gears to a 430 and reprogrammed to 410 (did not have 430 in programmer) and mpg showed 14 ish and speedo was off 7mph. Yesterday programmed it to 456 speedo was right on and showed 16 Mpg. So with all that info what I am really wanting to know is if odometer runs off same thing as the speedo. Cant calculate it by hand if it is wrong also..... Damn near confused myself typing that.