Many car rental/hire companies offers special rates that include kilometres travelled or give a certain amount of free mileage, so check out the figures below:

The distances between the airports and nearest cities in South Africa

Cape Town International Airport-22 kilometres (14 miles)east of the city (travel time - 25 minutes by car)
Bloemfontein International-10 kilometres (6.2 miles) east of the city (travel time - 15 minutes by car)
Durban International - 16 kilometers (10 miles) south of the city (travel time - 20 minutes by car)
O.R Tambo International Airport (Johannesburg) - 24 kilometres (15 miles) northeast of the city (travel time-35 minutes by car)
Port Elizabeth International Airport - 25 kilometers (16 miles) from the city (travel time - 30 minutes by car)
East London Airport - 15 kilometres (9,5 miles) from the city (travel time 20 minutes by car)

Kruger Mpumalanga International Airport (Nelspruit) - 22 kilometres (14 miles) from Nelspruit, 44 kilometres (28 miles) from Numbi Entrance Gate of Kruger Park and within close proximity to the major game lodges in the area.

Johannesburg to Sun City 137.68 kilometers
Cape Town to Durban: 1620 kilometers (1006.6 miles)
Durban to Johannesburg: 565 kilometers (351.1 miles)
Johannesburg to Cape Town: 1390 kilometers (863.7 miles)