Hey Steermatic fans,
I just went through the thread, congrats on the purchase bro.
I usually get 11-12KM/L with AC and around 12-13(at times 14) without the AC, I could possibly get better mileage once I get the Catalytic Converter Fixed. I am usually driving at 60-80 and RPM is usually at 2K or slightly higher.
I am surprised to see that you are getting 10KM, but then again there must be a lot of traffic.
I have stuck to the stock tyre that are recommended by the Honda for Steermatic, Also I had the engine replaced about a year ago, because the person I bought it from well didnt take care of it.
I am using Sell Helix HX7 5W-30, I had a terrible experience with Honda's oil gave me terrible mileage and the car just felt like it was dragging itself. I was recommended Quartz 4000 here as well.
Make sure that you are using a reliable petrol station.
Also if there is a good shop where you can your EFI things done ask them to reset your gear ratios to factory.
Most importantly if you have a manual for the car make sure to change the fluids on time.