I drive the same car but in the US. Does your car have the hybrid style wheels and spoiler on the trunk? I think some Canadian dealerships made those modifications to improve the fuel efficiency numbers. If you do, consider yourself lucky, because I'd love to have those built-in aeromods.
The only physics change I made to my Civic was upping the tire pressure. Over time I tried 36psi, 38psi, 40psi, and most recently 44psi, the max sidewall rating on my tires (your tires may be different if you have the hybrid tires, so double check). This makes a big difference. I don't know if you use SI units of pressure, and if you do those numbers won't be helpful, but starting off with something between the pressure recommended in the owner's manual (for me, 32psi) and the max sidewall (for me, 44psi) would be a good place to start.
What techniques are you using to drive? I have substantially increased my fuel efficiency in my Civic by shifting around 2500-3000RPM and not accelerating aggressively. I coast in neutral as much as possible. In city driving, I have found the Pulse and Glide technique to be very useful. I go to my target speed, shift to neutral, and coast for as long as possible. Also try to anticipate lights turning so you won't do a "Pulse" right into a red light. If you have a stop coming up, use engine breaking (keep RPM above 1500RPM to ensure the fuel injectors are cut off, and of course have your foot off the accelerator). In general it is better to coast in neutral if you can start far enough back. On the highway, keeping speed under 60MPH or 100km/h is very beneficial, both due to drag and the unfortunate fact that our 5th gears aren't very low. Shift into neutral down hills. Avoid cruise control (even in flat areas, I think our cruise control uses more fuel than it needs to). In cruise, try to use as little throttle as possible, to encourage the engine to enter "fuel efficiency mode" which you can read about here
Technical Overview of Honda's new R18 i-VTEC Implementation and here
Honda Worldwide | New 1.8l i-VTEC Engine . Minimize AC, heater, and fan usage.
I have been able to exceed 45MPG on highway trips which is about 3.8L/72km which is about 5.3L/100km. I also haven't changed my oil yet from the factory oil, so I anticipate that when I do that efficiency will improve. I know you already know most of what I said here based on your post, but hopefully you can glean some insight from this. I'm happy to answer any questions and glad we have another 8th-Gen Civic MT on the boards!