Choosing the Correct Engine Oil

Feb 12, 2014 | API, Engine Oil, ILSAC, Mineral oil, oil, SAE, Synthetic oil, viscosity, ZDDP

You thought we forgot to tell you about Oil selection in our previous Blog on oil viscocity? We didn’t forget, this is a whole new blog on choosing an Engine Oil just for you. We want to provide you with the tools to help you understand how to choose the best oil you can at the lowest price of course, however we have no control on what you pay for your lubricants, you will need to take that up with your supplier or search for an alternative. Our suggestion is look around and don’t be afraid to ask questions.

So what are we looking for? We are after an Oil that can reduce friction and not waste useful power by converting the kinetic energy into heat. We need an Oil that reduces wear by protecting (coating) the internal parts which otherwise could lead to lower efficiencies and degradation of the engine. This would lead to higher fuel consumption and decreased power and then possibly engine failure.

Vehicles come with an owner’s manual that provides you the information on the manufacturer’s specifications and certifications that are required for your vehicles oil. This should be followed, don’t choose your own oil unless you have an Old Vehicle. Old vehicles that have pushrod engines with Flat Tappet camshafts need to choose an oil that contains ZDDP (Zinc Dialkyl Dithio Phosphate) – Zinc additive for anti-scuff wear protection. Be aware that most oils today’s do not contain adequate levels on ZDDP, so may have look specifically for an Oil that does contain this additive or look for a racing engine oil with this additive.   

Engine Oils contain certifications from up to three different organisations. The American Petroleum Institute (API), the International Lubricant Standardization and Approval Committee (ILSAC) and the European Automotive Manufacturers Association (ACEA). API Ratings are a certification mark that is also known as the Starburst or Donut label. The information below indicates each rating.

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This information was used from API.ORG

Now back to Viscosity, a topic which we covered in our last blog Oil Viscosity and its importance.  Choosing a viscosity grade is going to depend on where you live. Temperatures play a large part in viscosity as the thin when heater and thicken when cooled. Engine start-ups are extremely important, we need to ensure the oil is thin enough when cold that it allows to flow through thin gaps in order to minimize metal to metal contact. The oil must be able to flow adequately at its expected lowest temperature.


What does the W mean? The W in between the viscosity grades (10W-30) indicates that the viscosity grade will be in Winter or when the oil is cold, in this example it is 10W. In summer or when at operating temperatures it will be 30. Most commonly used are 5W-20, 5W-30, 10W-30 and 10W-40. These cover most light-duty vehicles on the road today.

What type of oil should we use? Normally your owner’s manual will state what grade, API rating  and type of oil you need to purchase, however let’s give you a quick rundown on some differences.

Mono Grade Oil – These cannot use a polymeric viscosity index improver additive. Single grade oils are often referred to as straight-weight oils. They are used in old equipment and are not suitable for newer engines.

Mineral Oil –Mineral oils are your cheaper alternative to purchasing oil, they contain many variations of additives and a lot of VI improver. They consist of group I and II base stock oil.  

Semi-Synthetic Oil – These oils can be labelled as part, semi-synthetic or synthetic technology which means it contains a mixture of mineral and full synthetic base stock oil. Most of these oils have added VI improvers, the VI improver allows the oil to have the designated base oil viscosity when cold and the viscosity of the second grade when hot, thus making it a multi-grade oil.

Synthetic Oil – These are considered to be high-tech superior enhanced performance oils that have the capabilities of protection against deposit formation, superior lubricity at high temperatures, better or more even flow at low temperatures. They are made up of either group III, IV and V Base stock oils. These base stocks are higher in purity and therefore gain better property control over lower base stock oils. They have a higher VI over lower grades , with this higher VI, they do not need much VI improver additive added into the oil. This allows greater control over thermal and mechanical degradation of the oil as it ages. With this in mind Synthetics are almost double the price of your semi-synthetics.

This information should have provided you with the tools required to select an engine oil that will give you high performance, low fuel consumption, good start-up capabilities, low wear and stable viscosity. Always check your owner’s manual before purchasing oil to get the API rating, viscosity grade and whether it states to use a Mineral, Semi-Synthetic or Full Synthetic oil.

If you need to know more or have any questions, please contact us.

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