Oil Change Intervals

When should engine oil be changed? It depends on how and where you drive, and whom you talk to in the motor industry,

- Jake Venter

Driving on a typical short daily commute causes excess fuel and water (a product of combustion) to migrate to the engine sump. This can eventually form an emulsion called sludge, which can block oil-ways and thicken the oil to such an extent that lubrication ceases and the engine fails.

In recent years, an increase in the percentage of engines damaged by sludge has been reported in the US as well as in South Africa. In some cases, engines with very small sumps have been blamed. The oil often runs too hot and this causes the long molecule chains to break down and makes the oil more susceptible to forming sludge. It can also occur when the crankcase ventilation system is defective.

Oil change intervals have been under scrutiny over the past 20 years or so. Manufacturers would like to lengthen them, because oil stocks are being depleted. A longer service interval also sounds good in the showroom. Not long ago, many manufacturers advised changing the oil at 10 000km, but now 15 000km is almost the norm.