Read the whole thread ... I have an Alto too (2005), so far car has done 155000km done, on stock engine (without over hauling) It's too heavy on petrol, still running smooth but as per mileage it's on bonus running.
its too heavy on petrol and CNG Is not available. Kindly suggest me if I go for engine replacement which engine suits me for better consumption on petrol, and approx price of engine???