Suzuki: Sidekick conusmes alot of fuel, fuel mileage, gravel roads

Question
Dear David
i have two questions of what am facing with my car.
I drive suzuki sidekick 93 1.6l 16 valve engine, Automatic 4 speeds, milage 147,000KM

first question: it consumes too much fuel 36 liters drives me 225 KM only, i changed the sparks & filters & tuning the injections all that didnt work.

Second question: i bought the car with carborator engine and automatic gear with 3 speeds but i changed it to injection engine with automatic gear 4 speeds, after that when the car speeds reachs 80km and above it starts shaking.

Thanks

Answer
I have seen tremendous variations in fuel mileage that is dependent on many variables such as whether the owner idles the vehicle to warm it up before driving, whether the ambient temperatures are high or low ( for instance in -40 temp, fuel mileage can be reduced to half by warming up before driving) the speed at which it's driven - high speeds and city driving can be responsible for a more than 25% reduction in mileage, and others.  Driving on dirt/gravel roads is also a source of low fuel economy.  Vibration at speed is usually a drivetrain imbalance (tires, driveshafts, u-joints, and the like)
To get a fuel mileage reading that's accurate, the temp must be moderate (t-shirt weather), and the vehicle should be driven (no A/C) at a speed less than 80km/h on flat ground for at least 60 km to get an idea of what it's capable of delivering prior to judging whether there's a problem.