Rep Power: 0

Not sure if this is an issue, but the idiot light for my 2008 Civic DX engine temperature is showing 9 bars instead of 10, thus the thermostat is running a bit cooler than optimal. Just wondering if this is worth attending to, re best gas mileage, etc., or just leave it be until it goes farther off kilter. Any thoughts?

If the thermostat is to be replaced, is it easily done by a home mechanic with simple tools? (my previous car was a Nissan 300ZX, and it took a lot of work and R&R of multiple parts to get the themostat out of that beast!)

Thanks!

 
Rep Power: 517

That can be considered average in cold weather.
There is service info stating this is normal.
Found this copy posted elsewhere on the net:

Honda Service News Article, Feb 2010, states

- Temperature Gauge Reads Low When It's Cold Outside -
In very cold weather, your customer might notice that the engine temperature gauge appears to reach the normal operating level a little slower than it would in warm temperatures. This slower movement shouldnt be mistaken for a bad thermostat or any other cooling system problem, as this is typical operation of the temperature gauge. This is because the temperature gauge doesnt operate in a linear fashion like a fuel level gauge does. Check out the example below of this logic shown on a 2006-10 Civic:
Gauge segment 1 doesnt show until engine temperature reaches approximately 132°F or 56°C.
Gauge segments 2-9 are approximately 138-165°F or 59-74°C.
Gauge segments 9-11 Normal operating range is 170-222°F or 77-106°C.
Gauge segments 12-20 are approximately 228-249°F or 109-121°C.
Gauge segments 21-22 are approximately 255°F or 124°C.



HTH