I am about to change my diesel fuel filter. The 5 x T25 screws should be tightened to 5nm. How critical is it that a torque wrench is used? If I made a mental note of how tight they feel when removing them, and then try to get them the same when reassembling, wouldn't that likely be good enough?

There is a danger that if you over do the tightness you will strip out the threads. The fuel filter housing is aluminium bodied so sure, make a mental note but there is a higher risk you will overtighten.

 

5nm is a 'light' pinch up tightness, if you are concerned, then use some semi-permanent loktite to keep the screws in place.

That's very helpful, thank you!