Samit Patel took five wickets and Andrew Flintoff hit 78 not out to inspire England to a 126-run win and wrap up the series comfortably.
England are now chasing only the second 5-0 series win in their history after they triumphed over Zimbabwe by the same margin in 2001-02.
Pietersen said, The 5-0 thing puts a lot more extra pressure on us as it would take us up to second in the world rankings. That is the kind of pressure we want pressure is a privilege and if we win 5-0 it takes us right up to the top. It is something we have talked about and if we deliver we can win 5-0. The dressing room is very happy place.
We are putting pressure on their batters and playing to our potential. Were hitting their good balls for four and doing a really good job on them.
I know South Africa really well and they wanted to beat us. They are very proud people and stubborn people.
South African stand-in captain Jacques Kallis said, The cricket we are playing is not good cricket but England are playing unbelievable cricket. They are one of the best one-day sides we have played against recently. Flintoffs 77-ball innings and 31 from Patel carried England to 296-7 from 50 overs and South Africa were never up with the rate as they were bowled out for 170 with Patel taking 5-41 to cap a memorable fourth international match. Patel said, It has always been a dream to play for England. As an individual you couldnt ask for more. I played against South Africa for the Lions and although it was always going to be tough they knew I could bat.
Flintoff, adding to the 78 he made in the first game at Headingley, and relishing his role at number five put on a free-scoring partnership of 74 for the sixth wicket with Patel that took the game away from the South Africans.
His recent form with the bat is another triumph for new captain Kevin Pietersen who has promoted the all-rounder up the order and persuaded Steve Harmison, a crucial figure in this series, out of ODI retirement.
Flintoff survived a nasty blow to his temple on 38 when he was late on pulling a Morne Morkel bouncer but recovered to hit nine fours and a six. The pick of the South African bowlers was Johan Botha who took 2-35 from nine overs with his spin.
After being put in Englands Matt Prior played and missed during the early overs but found his range when he clubbed 14 runs off Makhaya Ntinis second over including a six over long on from a free hit. Ntinis first five overs disappeared for 47 but stand-in captain Jacques Kallis forced a breakthrough when Morne Morkel had Prior caught off a top edged pull that Herschelle Gibbs ran round to catch.