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2010 Mercedes-Benz GLK
2010 Mercedes-Benz GLK

You & Your Car

Oil changes have changed over the years Add to ...

QUESTION: For the last 40 years, I have changed the oil in my car every 5,000 km. My latest car (Mercedes GLK350) indicates the oil doesn't need changing for some 20,000 km and, in fact, the garage is quite reluctant to change it earlier (even though I pay for it). So, which is it? Does it pay in the long run to change it every 5,000 or even every 10,000 km or do I wait for the engine electronics to tell me when.

We drive in Brampton area and Mississauga mainly with a day trip of around 20-30 km each way on Highway 410 and side roads in rush hour.


QUESTION: You don't see as much nowadays about changing or topping up oil. Are today's engines that much better?


ANSWER: Yes, engines are indeed much better today.

The manufacturing tolerances in place today were not even imagined, let alone attainable even a few years ago. Robots and electronics have greatly reduced the variances in everything from the holes drilled in engine blocks to the gap in bearings and everything else.

Suppliers are placed under much greater scrutiny and their materials are required to meet vastly higher standards. Elaborate tracking methods allow manufacturers to track down a supplier or plant when a problem is reported, allowing corrections to made within weeks rather than the next model year.

In the old days, the motto was "build it and let the dealer or customer fix any problems." With today's demand for quality and surveys such as those conducted by J.D. Power, manufacturers can no longer get away with that.

The other issue is that the lubricants have been greatly improved.

Engine oils actually serve three roles:

1) They provide a layer of lubrication between two surfaces, preventing wear and reducing the heat caused by friction.

2) As the oil circulates through the engine, it picks up and carries away harmful little particles caused by wear and deposits them in the filter.

3) Because it circulates through the engine, oil also serves as a coolant, absorbing it and releasing some to the atmosphere and through the oil cooler.

The reason we need to change oil less frequently is that modern oils retain their lubricity longer and do not become as easily contaminated by particulates and harmful gases resulting from the combustion process.

The reason we do not have to top up or replace lost oil is that today's engines are assembled with more care, meaning fewer leaks.

If oil is not leaking from an engine, line or fitting, it has to be getting into the combustion chambers somehow and going out the tailpipe. The most common way this happens is through the piston rings or valve seals, both of which are unlikely to fail until the engine has attained accumulated extremely high mileage.

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Electric power steering helps to improve fuel mileage

QUESTION: Why are manufacturers using electric power steering? Isn't that placing extra demand on the battery which is already taxed by all the electronic gadgets on today's cars?


ANSWER: The simple answer is fuel mileage.

Electric steering allows car makers to get rid of a heavy hydraulic pump and the attendant hoses, belts and hardware. Not only does this save weight, it also means the engine isn't turning that pump all the time.

We only need the power assist when turning at slower speeds, yet with a conventional system, the engine is turning the belts and pump the entire time in order to maintain pressure in the system for when it is needed. Called parasitic loss, this extracts a tenth of a mile per gallon or so and in these times of seeking every single bit of mileage, getting rid of the weight and drag on the engine is a big help.

Early systems were pretty nasty with no feel and too much assist but the more recent ones benefit from experience and more computer programming. The power does indeed come from the battery but only when the engine is running and the alternator is replacing that energy as it is being used.

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