Q. What is the ideal speed to drive in highways to get best mileage on C 220d progressive. Also should I go for diesel or petrol with just Rs 5 difference in per litre price - C-Class?

If the comparison is based on the diesel vs petrol, generally, the petrol cars are prefered if the average daily run of the car is less than 50/60km as per the calculation taking into account the maintenance cost and fuel cost. The diesel cars are prefered to be driven more than petrol cars due to good mileage and more torque. Generally, the car should be driven in the range of 90kmph to 110kmph(approximately) to get the best mileage figures on the highways.

First I recommend to buy petrol bcuz it's best in life. Speed could be maintained at 140 to 160 on highway for better mileage.

I do not know