In engines, there is some exposure of the oil to products of internal combustion, and microscopic coke particles from black soot accumulate in the oil during the operation. Also the rubbing of metal engine parts produces some microscopic particles from wearing on surfaces. Such particles could circulate in the oil and grind against the part surfaces causing wear. The oil filter removes many of the particles and sludge, but eventually the oil filter can become clogged, if used extremely long periods.
Motor oil changes are usually scheduled based on the time in service or the distance that the vehicle has travelled. These are rough indications of the real factors that control when an oil change is appropriate, which include how long the oil has been run at elevated temperatures’, how many heating cycles the engine has been through, and how hard the engine has worked. The vehicle distance is intended to estimate the time at high temperature, while the time in service is supposed to correlate with the number of vehicle trips and capture the number of heating cycles. Oil does not degrade significantly just sitting in a cold engine. On the other hand, if a car is driven just for very short distances, the oil is not allowed to fully heat-up, and contaminants such as water accumulates in the oil, due to lack of sufficient heat to boil off the water. Oil of this nature, just sitting in an engine, can cause problems.
We would recommend an intermediate service engine oil and oil filter change every two years or 12,000 miles and a full service every 24,000 miles and on alternate years from the intermediate service. This, of course, depends on the vehicle you are driving, and on the trips/distance you travel. Should you regularly travel short trips and not allow the oil to heat-up and run for a time at high temperatures’ it may be necessary to change the oil more frequently than if you took longer, less frequent trips.
Many manufacturers have engine computer calculations to estimate the oil’s condition based on the factors which degrade it, such as RPM, temperatures, and trip length; one system adds an optical sensor for determining the clarity of the oil in the engine. These systems are commonly known as Oil Life Monitors or OLMs.
At R&M Mechanics, when booking either a Full or Intermediate Service we can also offer an MOT at a reduced rate of £20, rather than the standard rate of £47.