The only guide to Engine Oil you need

To most people, engine oil is just one of those substances that goes towards keeping your car in perfect working order. However, many disregard the true importance of this murky brown liquid and are not only unaware of its uses, but also the problems that can arise if it is used in the wrong way.

If you sit firmly in this category and have always wondered what the numbers and letters mean on the front of the bottle, here’s our guide to help bring you up to speed.

What does motor oil do?

​Before you can begin using motor oil in the appropriate way, it’s imperative that you understand its functions within the engine system. Motor oil has a number of uses. As well as alleviating friction and grinding between the many metal surfaces in the engine, it also transfers heat away from the combustion cycle to help the engine regulate a mean temperature. Engine oil also fights against the build-up of dirt and deposits to prolong the life of the engine.

What is the difference between conventional and synthetic motor oil?

Motor oil is available in two different categories: conventional and synthetic.

The main difference between the two is performance; synthetic lubricants contain more highly refined base oils than those used in conventional lubricants, and therefore are able to protect the engine for longer – as much as three times longer in fact. Conventional oils have molecules of differing sizes, unlike in synthetic where they are more uniform – therefore synthetic will offer a lower possibility of friction.

As synthetic oils are significantly more expensive than conventional oils, a modern alternative is the synthetic-blend, which combines the two to provide protection at a price which meets in the middle of the two.

What do the numbers and letters mean?

The next topic is the numbers and letters, which should never be overlooked. You might have seen ‘10W-40’ or ‘5W-30’ on the oil packaging before – here we explain what it all means.

The numbers represent the viscosity of the oil, which is essentially the thickness of a liquid. The higher the number, the thicker the oil, and the thicker the oil, the slower it will flow through the engine and the better lubrication it will provide. The numbers with the letter ‘W’ refers to ‘winter’ and is used to reflect the oil when it has been tested at a colder temperature. For example, ‘5W-30’ oil has a viscosity of 30 at 210° (the approximate temperature of a running engine) but has a viscosity rating of 5 during winter environments. The higher the number, in theory the better protection it will provide. However, it’s not as simple as getting oil with the highest numbers because each vehicle will have a recommended type of oil. Using an alternative could cause many problems for the engine and end up costing, so always use the type that your manufacturer suggests.

For a helping hand when shopping for a Ford car at one of our Salisbury, Poole or Yeovil-based Ford dealerships, here are the correct motor oil recommendations for all current models in the Ford fleet.

What do the experts say?

To find out more about the importance of choosing the right motor oil, we got in touch with the experts at Rock Oil. A company that has been supplying high quality oils for all markets since 1928, their expertise in oil is second to none. Here’s what they had to say about why engine oil is so important:

“Motor oils are incredibly complex and very OEM (Original Equipment Manufacturer) specific today. It is impossible to select one motor oil to cover all vehicles, therefore, selection of the correct grade & specification is absolutely vital. Almost every OEM today has their own requirements for the motor oil used in their engines.

Of course wear protection, soot/sludge handling, cold temperature flow, corrosion protection etc. are still extremely important, however, we have to achieve all of these whilst addressing a number of key challenges with a modern motor oil:

• Drain intervals are longer than ever and very specific according to each OEM.

• The oil has to be compatible with exhaust gas after-treatment devices (e.g. TWC and DPF) fitted to comply with the latest emissions regulations (EURO emissions in our region), so there are now limits on the SAPS (Sulphated Ash, Phosphorus & Sulphur) levels allowed in the oil without affecting overall performance.

• Fuel economy is also a significant focal point of today’s vehicles, and the correct motor oil is right at the centre of that. Motor oils are becoming lower in viscosity to improve fuel economy (less internal engine drag), to the point where the SAE has recently introduced SAE 0W-16 and 5W-16. These are the lowest viscosity motor oils ever produced for road vehicles and it is all in the quest for fuel economy, but of course without affecting the life of the engine.

  • Martyn Waterhouse, Rock Oil Technical Director

How much oil do I need to use?

As already mentioned, motor oil provides a protective layer to prolong the life of the engine. Despite its positive credentials, using too much oil at once could cause a serious problem and lead to lasting problems with other engine components. This is the main reason why there’s a dipstick, and you can use the minimum and maximum marks at the bottom to measure how much oil is in the system.

When the engine is cold, remove the dipstick and wipe it off with a towel, now place the dipstick back into the engine and pull it out again to determine the true level of the oil.

If the amount is slightly low, unscrew the oil cap and, using a funnel, slowly add the oil. Wait for a minute or two for the oil to trickle and check the dipstick again. Keep adding the oil until the measurement is just below the maximum mark before firmly screwing the oil cap back on.

How often should I change the oil?

Not long ago it was strongly recommended for people to fully replace the oil in their vehicles every three months or every 3,000 miles – depending on which came first. Full oil changes can be carried out as part of our Ford servicing packages. However, the arrival of synthetic oils means that some cars can now go as far as 10,000 miles without a change. When we asked Martyn Waterhouse for his advice, he made it clear to base this on the manufacturer’s recommendations:

“The OEM recommends the drain interval for the motor oil in their vehicles, and apart from the very rare exception, we advise the customer to adhere to these recommendations.”

  • Martyn Waterhouse, Rock Oil Technical Director

If you want to find out more about the correct use of motor oil or perhaps some of the methods you can use to prolong the life of your Ford vehicle, pay a visit to our official Ford dealership in Dorchester and other locations across Southern England.

This content was written by Ben Edwards. Please feel free to visit my Google+ Profile to read more stories.