The thermometer in my TSX is usually 15 to 20 degrees off when I get in the car and it takes about 15 to 20 minutes before it reads correctly. I know it is not going to be right on at startup but isn't this excessive. Is it normal for it to be so inaccurate?

 

Mine is usually off too, but only by about 10 degrees. I though it was because my grarage is always warmer that the outdoors.

 

The manual says it won't read correctly when its parked but you should get a pretty accurate reading (+ or - 2 deg.) after driving it for a few minutes. There's a way of calibrating the readout if its off. Again, check the manual.