HI EJ
I reckon it's quite subjective, personally, if you have decent oil in the car then changing the oil can be done every 20 000km (12 500 miles) when it goes in for service. But, theoretically, the oil does become tainted/damaged during that period, this then having aŽnegative effect on the engine (negligable but there nonetheless) that is why some guys (me included) will change oil halfway (roughly)through the service interval (10 000km or 6250 miles)Purely to keep the engine in a more 'optimal' condition. Just my thoughts, Cheers
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Jos
Pearl White ST
Pretoria South Africa