It’s not that long since oil had to be changed at 3,000 mile intervals. Until the 1970 oil crisis this was the norm – oil was cheap, motorways were still relatively new, annual mileages were still low for most of us so a 3,000 mile service interval wasn’t particularly onerous.
Apart from lubricating and cooling the engine innards, the oil absorbs a lot of nasty corrosive by-products of burning fuel that would otherwise lead to rapid engine wear and years ago, after 3,000 miles the oil would be saturated with this toxic goo and need changing.
Today’s engines use far less fuel and burn it more efficiently, producing less of the nasty by-product, and the oil has been developed so that it can absorb a lot more of it. Given the high price and increasing scarcity of oil, it makes sense to extend the oil change intervals provided the car spends much of its time running at full temperature and high efficiency rather than doing lots of short, inefficient journeys.
For cars that sit in commuter congestion for much of their life, the service interval is time based – usually a year these days. But the engine management computer has a full history of how the engine’s been run, so it can easily work out the optimum time for an oil change. It’s far better that the car should tell the owner when maintenance is due rather than having a strict mileage or time based regime that takes no account of the conditions the car has been used in – it saves waste for high mileage cars and saves wear for low milers. (Always assuming the correct oil is used, of course, which is why a close scrutiny of the service record is increasingly important for second hand car buyers.)
So, we should see more and more cars with a variable oil service interval indicated by a dashboard display and dependent on type of driving the car does. It’s good for the engine, the environment and the owner’s wallet. However, having an extended service interval for oil changes doesn’t necessarily mean that everything else on the car will last longer – and brake wear is an example. There’s nothing wrong with a dashboard indicator telling the owner that the brake pads will need changing in the next 1,000 miles, just as tyres carry wear bars in the tread to tell us when they are nearing the end of their useful life. In fact, it would be useful if manufacturers developed this concept a bit further for the other items that wear out from time to time – exhausts and batteries being the main ones.
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Many a breakdown would be saved if we had a reliable advance warning that we needed a new battery (provided we take notice of it, of course). Overall, changing wear and tear components only when they need changing instead of according to a strict mileage regime, makes a lot of sense and saves a lot of waste. Why change brake pads at a service interval if they have 3,000 miles of life left in them? Let the sensors do their job and maximise their life.
So, let’s have more manufacturers building “service due” indicators into more systems in cars. And as motorists, we should get used to taking notice of the dash warnings; instead of being disappointed that brake pads might need changing between oil services, we can relax and let the car take care of itself.