Hi all, I'd like to know the engine's compression level and fuel consumption are related to each other. For instance, if the compression is poor, can it be a reason for high fuel consumption (low mpg) ?

I'm experiencing a late start issue (planning to do a compression test very soon) and very poor mpg in my 2007 auto RX-8. Recently bought it and later got to know it doesn't have a thermostat. Can it be a problem? I need to check if the battery is ok as well. If the battery is poor can it be a reason too?

 

Since there is no thermostat it could be to cold to be efficient with the fuel. There is an optimal temp for the engine to work efficiently.

 

A poor battery will cause long starts but not change fuel consumption. Poor fuel consumption is often associated with bad ignition coils and/or a clogged catalytic converter, which together cause engine damage and loss of compression.

What happened to the thermostat? Did someone have overheating problems and tried to fix it poorly?

 

That's what I'm guessing. I'm getting P0037 code which is related to O2 sensor.