I have an 3door Toyota RAV 1996 ... what will be the rate per kilometer for fuel consumption This is my own 'old' car , well loved and looked after!

The Engine Control Unit (ECU) in a 1996 Toyota RAV4 is not reprogrammable, but can be replaced with a new or remanufactured unit. However, if your RAV4's fuel consumption is high, it is likely due to other issues, such as a dirty air filter, a faulty oxygen sensor, a clogged fuel injector, or a worn spark plug. You should have the vehicle inspected by a qualified mechanic to determine the cause of the high fuel consumption.

i doubt very much if it would be running at 1 litre per 1 kilometer
at very rich combustion stops at 10:1 as the fuel puts he fire out
I'm not disputing your figures just I would be looking for a fuel leak from a hose , filter leak or leak in the tank or some one stealing fuel
run the fault codes
check the fuel system from tank to manifold

http://workshop-manuals.com/toyota/

Might be something on here

Write your answer...may be 1 ltr. : 18 km.

First, are we talking about a Nissan or a Toyota? (You posted your question in the Toyota section).
Second, your mileage works out to 7 miles per US gallon (sorry, I can't think in liters and kilometers). SOMETHING IS LEAKING, because there's no way a modern engine could use that much fuel if it was running in normal or semi-normal fashion.
What were the "few things changed?" I suspect a leaking fuel hose or connection.

When was last tune up? Plugs, wires, all fluids & filters - especially fuel filter?? I'd start there and run a good fuel system cleaner through it.

That is HUGE for a 1.3 L engine. I seriously think you must have a fuel leak somewhere.

is there a check engine light on?
spark plugs, wires, filters, tire pressure, sensors and alignment, they all affect your gas mileages.

Cannot confirm. Need to verify other sensors are functioning properly--map sensor, tps, maf...is the engine light on?

try changing the oxygen sensors this will make the biggest difference in fuel consumption. also depends on weather conditions and fuel quality in your area i know where i am at winter fuel runs alot worse then summer fuel because of the emission control additives they put in it.