Hello Paul, I have owned a 2002 Honda CRV for the last four years and it has been largely okay. One and a half years ago I got a job out of Uganda and have only come home for two weeks. I have not done an oil change for all this time because my oil still has 80 per cent service life having done only 1,010kms since the last oil service. Is it necessary to change the oil because its looks darker yet it has worked for a short time? Karamagi

Hello Karamagi, engine oils begins to change colour from the moment its first run in your engine and this may not necessarily be a reliable indicator of old age or need to replace immediately. Oil becomes darker from the first day of operation due to its primary roles of lubrication, metal sheer protection, cleaning and transporting contaminants and deposits as well as cooling hot, fast-moving engine metallic components.

Engine oils expire when they are put in the engine and get contaminated by combustion acids and dirt. The oils are also degraded by oxidation from exposure to air and experience with thermal break down from operational heat or stress as they carry out the above primary functions. Overtime, engine oil will suffer molecular structural breakdown (degradation), change viscosity (thickness and ability to flow easily) as well as form sludge.

How fast oil degrades or reduces its performance attributes will depend on the standard of refinement and blending from base oil, with performance enhancing additives. Standard mineral engine oil does not withstand the above degrading elements as well as the synthetic engine oil. Synthetic engine oil is further refined, distilled, purified and broken down. The oil molecular structure of synthetic engine oil is rebuilt and customised to suit specific performance and protection needs in extreme heat or cold conditions.

How often you need to change your engine oil is determined by the car manufacturer’s recommendations, the condition (wear and tear) of your car engine and the operating conditions (environment). The oil drain intervals for mineral grade engine oil are shorter (3,000-5,000kms) than the synthetic grade oil (10,000-15,000kms). All engine oils will also degrade overtime, regardless of the engine not being used, mainly due to oxidation.

It is recommended to consider draining all engine oil and replacing it with new oil after parking for extended periods such as over a year. Even the best synthetic engine oils have a shelf life of about 5 years if sealed and stored in controlled temperature conditions. When used in a car engine and parked for long durations such as one and half years, even synthetic engine oils may need to be renewed.

Some car manufacturers such as Mercedes and Land Rover design the cars with oil service counters which consider both time and mileage, whichever comes first, to recommend oil service.

My automatic gearbox shifts violently

Hello Paul, I own a Toyota Highlander/Kluger 2002 model. Am I supposed to feel the revolutions within the transmission as it is changing gears, say when I am approaching humps? Also, when I am driving above 60km/h and there is an abrupt emergency to cut speed but just for a few seconds, why do I feel a knock still in the transmission like it has changed gear when I accelerate? Kaweesa.

Hello Kaweesa, your Toyota Kluger automatic transmission (gearbox) may have a clogged transmission filter and dirty fluid, faulty gear solenoids, a damaged gearbox pump or a faulty automatic transmission computer circuit. It is abnormal for gears in an automatic transmission to shift upwards or downwards violently or with difficulty as you have described. It is easy to misdiagnose the above symptoms as a failure of automatic transmission mountings or suspension.

A computer diagnosis is recommended to rule out electrical failure, while a physical inspection of the ATF and filter will help to confirm their working condition. Signs of metallic debris should not be ignored. An automatic transmission relies on transmission fluid (ATF) to engage selected gears.

This fluid provides hydraulic pressure which helps to engage different gears as well as lubricate and cool the fast moving metallic parts.
ATF remains in suspension to transport debris and deposits for filtration by the gearbox filter. The condition of the oil and filter are critical for the smooth operation of your gearbox.

The electrical system of the gearbox is controlled by a computer which helps to synchronise selected gears with the engine demand (engine gear ratios) for seamless shifting from low to high gears according to driving needs.

Critical in this system is the condition of mechanical components such as the pump, planetary gear sets and other metallic components which need to be lubricated and cooled by the ATF.

A restriction of ATF flow due to failure of solenoids or a clogged filter can cause rough or violent engagement of gears and mechanical damage. The computer uses a circuit to communicate with gear solenoids which release ATF (like water taps) to the selected gear pack when you engage reverse or drive or when the engine demands a range of gears according to your driving needs. All of this works smoothly if the ATF, mechanical and electrical components of the gearbox are okay.