All you need to know about engine oil quality

The average motorist does not know what the technical gobbledygook on a can of oil means. And he doesn’t want to know. 

But he does want to know what oil to put in his engine. So rather than a translation of the codes for weights and grades of oil, here’s a simplification: All motor oils from all the major brands are very high quality indeed. You can put almost any modern engine oil in almost any vehicle and it will do its job adequately. It will lubricate moving parts, reduce friction, reduce wear, and reduce heat build-up. 

What is also true is that the higher the grade of oil you buy the better it will do those jobs. 

That means that the best oil for your car is the best oil that man can make and money can buy. That means the most expensive grade available in the petrol station or garage you go to. There is no doubt that it will deliver better lubrication than lower grades. The question is how much better, and how much difference it will make to performance, reliability, durability or running economy. 

Stick with the principle that top grade is better (and will save money in wear and repair) but it is also more expensive (and will cost more money to buy). 

PRICE PENALTY

If optimum performance is your priority, the cost doesn’t matter.

Put a better oil in, and you will get a better result out. 

If optimum economy is your priority, you will have to weigh up how much the higher grade oil will save (in fuel consumption and engine life) against how much extra it costs. 

An exact answer to that calculation would take Albert Einstein, Stephen Hawking and a team from the Right Royal College of Quantum Physicists and Thermodynamicists about six months to work out. Fortunately, you and I can calculate a good enough answer in about six minutes. Like this:

 *  The difference between good oil and the best oil is usually marginal. Real, but small.

* The difference is greatest in very high performance engines  and/or engines which are driven very hard and/or which operate in very severe conditions. 

* The difference is smallest in older and/or low performance cars that are driven gently, under light loads and in not-so-hot-or-harsh conditions. 

So, armed with those principles, do this:

*  Find out what grade of oil the manufacturer recommends for your car. Never use a lower grade than this. 

 * If you class yourself as a relatively gentle user, the price penalty you pay on a higher grade is unlikely to be recovered through better fuel economy or longer engine life.

 * If you class your driving style or conditions as harsh, then choose an increasingly higher grade of engine oil – the harsher your rating, the higher the grade, up to the highest you can afford. In extreme conditions, the extra cost of a higher grade will be more than off-set by gains in operating efficiency and longer engine life.