i have optra 1.6 ,this is mileage problume it mileage is 3km-4km per litr i have patrol car plz sovaution this

If you have an old used police car, you have what is called a beater. It has been as we way in the old west, ridden hard and put away wet. I'm sure the oil was changed on time, tires inflated correctly, tuned when needed. It has been driven very slow and at times as fast and hard as it could go. Police cars in urban areas need acceleration, so low gears are put in to compensate for small engines. The only way you will achieve better petro mileage is to change the rear end gears and possibly the transmission. The EFI also may have been modified to put more fuel into the engine for more power. The suspension is beefed up so the weight of the far is more than a civilian sold vehicle. What you saved in buying an old police car, you're making up in increased gas mileage. CAVEAT EMPTOR!