I think the engine is actually warming up, just the gauge thing is off. I started the engine and popped the hood, and feeling to see if engine was staying cold. After a few minutes, it was quite warm. (but im not sure how warm its actually supposed to be to compare)
Mechanic said he can do it all including parts for $30, but the last integra he changed a thermostat for because it had the same problem, ended up fcking up a while after. Cant recall exactly what he said, but it was something because of the old age of the car, the diameter of the hole where you change the thermo got smaller and so on i cant remember.
I will do the 2 full tanks like he said and record the L/100km, and will see what he says. He acknowledges that it's eating more fuel than it should, but reluctant to change it cos of past experiences with tegs fckin up after changing.

