Ultimate Guide to Engine Oil | Autance

If you love your car, then you know just how important its engine is. Taking good care of the car’s…

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Ultimate Guide to Engine Oil | Autance © Ultimate Guide to Engine Oil | Autance

If you love your car, then you know just how important its engine is. Taking good care of the car’s engine is a must and an inherent responsibility for every individual who owns a vehicle. And one of the best ways to care for your car’s engine is by using only the highest possible quality of oil that we could ever put inside this marvel of a machine. Consider the oil as the lifeblood of your engine. Without it, you can almost as certainly say goodbye to your ride or a myriad of expenses having the engine repaired or worse, replaced.

The Importance of Engine Oil

There are many reasons why only the most appropriate high quality engine oil should be used in today’s cars. Here are some of the more common reasons why engine oil is important.

Prevents friction

This is inarguably the most important reason why you need to put the right kind of oil into your engine. Just look at it this way. Imagine your knee as the engine and the synovial fluid inside your knee joint as the oil. Now try removing the synovial fluid from your joint and you can actually hear your bones grinding together. You will also not be able to move because it will be very painful.

While the engine is not a joint, it is essentially made up of moving parts. And it’s not just any ordinary moving parts that we’re talking about here. You are looking at a multitude of metallic parts that can easily heat up because of friction. As such, the primary purpose of engine oils is to lubricate these moving components including the various mechanisms that are responsible for their activities to help eliminate friction. And you already know that whenever friction is involved, heat is also present. This is one reason the term fry an engine came about.

Preventing friction between these moving metallic parts will help prevent them from grinding against each other, helping avoid damage to the components, and saving you from potentially costly repairs. In worst cases, you might be better off getting a new car.

Channels heat away from combustion cycle

This is a natural consequence of the prevention of friction. It is inadvertent that heat will still be generated because of the movement of these individual metallic parts. The good thing is that the oil also serves as an insulator so that any heat generated by these moving parts will not affect the combustion cycle. We know that the primary purpose of the engine is to produce highly controlled explosions or combustion inside its cylinders. Now, if extraneous heat were applied into these controlled explosions, you can just imagine how problematic it will be for the engine.

Acts as a magnet for combustion byproducts

The fuel that enters our engine through the fuel injection system or even the carburetor in older car models is essentially composed of chemicals that, when ignited to create the controlled explosions we have come to associate with car engines, can produce chemical byproducts because of the resulting chemical reaction. This is where engine oil can help. Since these types of fluids are slick and highly viscous, they have the capability to attract and suspend all the unwanted byproducts of combustion. For example, engine oil can put acids and silicon oxide into a thick suspension so that these will not go into the other parts of the engine and cause unwanted damage.

Minimizes oxidation

We know that fuel has to be mixed with air to produce combustion. And you know what air contains? Oxygen! And whenever there is oxygen, the chemical process of oxidation is not far behind. Can you imagine the internal combustion engine showing signs of corrosion everywhere? While we cannot stop oxygen from entering the engine (remember, we cannot screen oxygen from the other gases entering our air intake) we can, at least, minimize its oxidative effects by using the right engine oil.

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Deciphering SAE Ratings and Viscosity of Engine Oils

If this is your first time to buy oil for your car’s engine, chances are you’ll be confused about the SAE ratings of the various engine oil products you see on the shelf of your favorite auto supply store. Don’t worry, you’re not alone. The thing is that while the quality of car engine oil really matters, of equal importance is its grade. This is where the SAE Rating of any given product comes in.

SAE stands for the Society of Automotive Engineers. The SAE rating actually refers to the function and viscosity of any given engine oil. Viscosity, if you can remember your physics, is academically defined as the ability of a fluid to resist gradual deformation through tensile or shear stress. It’s quite a mouthful. But here’s a much simpler definition – viscosity refers to the ‘thinness’ or ‘thickness’ of a fluid. As such, a highly viscous fluid is one that is ‘thick’ while fluid with low viscosity is described as ‘thin’. Just think of blood being thicker than water, with blood having high viscosity and water having low viscosity.

So what does this have to do with the engine, you ask? Well, have you seen oil in the winter? It can turn solid, right? That’s exactly the same thing with oil. As such, engine oils must be kept as thin – low viscosity – as possible when it is cold. When it is hot, oil can become very thin because it somehow ‘liquefies’. As such, engine oils must also be designed to be as thick – high viscosity – as possible when it is warm. Now let us apply this by citing an example.

Let us say you have a fully synthetic oil whose SAE rating reads 5W-30. The 5W means that the oil has been tested at colder temperatures and that it has a viscosity grade of 5 and with the “W” referring to winter. The 30 reflects the viscosity grade of the oil when the engine temperature is at 212°F. If you live in a colder environment, a 5W rating oil will be able to start your engine a lot sooner than a 10W rated oil. This is because the lower viscosity oil in such temperatures will be able to circulate throughout the engine much faster than thicker oil. Remember, ‘thinner’ oil must be used in colder temperatures otherwise they turn into treacle. The warm viscosity rating of 30 means that it is already this thick (30) once the engine reaches the boiling point.

Here’s the trick. If you have to cold start your engine every day, you’re better off with engine oil that has very low W viscosity rating, say 5W or even 0W. There’s a reason why a low viscosity rating is preferred during cold starts. The quicker the oil is able to flow, the less time for dry running. Reduction in dry running times means less engine wear. This has been proven many times in various trials. Of course, you can still run your engine without engine oil. But after 15 minutes or so, automotive trials have shown your engine will already start breaking apart. Push it some more and it seizes altogether. So, the quicker you get the oil to flow throughout every part of the engine, the less time that you will have it dry running. This is one way to protect your engine.

Now, there are also engine oils that don’t have the winter viscosity rating. For instance, you will see SAE 30 instead of a SAE 5W-30. What this simply means is that the engine oil has never been tested in cold temperatures. It was only tested in the presumed operating temperature of engines at 212°. As such, SAE 30 has technically the same warm viscosity rating as a SAE 5W-30 or even SAE 10-30 since both have 30 as their warm viscosity rating.

So the next time you look for the engine oil as specified in your owner’s manual, you now know why they recommend such SAE rating for your car.

Different Types of Engine Oil

In the preceding section we have already deciphered what those numbers in the SAE ratings mean. Actually, there is another use of these ratings that pertains to the three fundamental types of engine oil. You see, with the advances in automotive engineering, motor oils today are becoming more efficient in the way they protect every moving part of the modern engine. Here’s a look at the three types of motor oils.

Fully synthetic

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This type of motor oil is fully synthesized or produced in a laboratory setting by a licensed chemist complete with the lab coat, safety goggles, and everything else; well, you get the idea. There is actually one way you can determine if a product is fully synthetic or not, even without looking for a marking that says it is “Fully Synthetic”. If its SAE rating is 0W-30 or 0W-40 or 5W-40, it is fully synthetic oil. How else can you ensure the accuracy of the winter viscosity grade without really tinkering with the chemical composition of the oil?

Fully synthetic oils are preferred primarily for their fuel efficiency which typically translates to better gas mileage. Since it is especially formulated in a lab setting, you can expect the product to draw out max power and optimum performance from your engine. It is also better at protecting your engine against the buildup of mineral deposits as well as protection against wear. It also helps ensure excellent cold starting and guarantees quick circulation of the oil throughout the engine even in freezing temperatures. More importantly, however, fully synthetics can get all the mechanical parts of your car’s engine up and running in no time at all.

There are other benefits as well. Since it is more resilient against degradation, oil changes can be less frequent. If you need to change your regular oil every 3,000 miles or so, with a fully synthetic you only need to change it every 7,500 or even 10,000 miles. We know of a particular instance where the oil change occurred after about 25,000 miles, although we strongly advice you against pushing your engine this far.

The downside is fairly obvious. It is definitely more expensive than your regular oil.

Synthetic blend

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There are some of us who would rather stay on the middle of the road. Fully synthetics are exceptional when it comes to fuel economy and performance. Unfortunately, it’s weighed down by its price. Mineral-based oils or conventional motor oil can be cheap, but it doesn’t really offer your engine that much, plus you have to change oil very often. As such, a good compromise would be a synthetic blend or what many would refer to as the semi-synthetic.

This type of motor oil is a combination of conventional motor oil and synthetic oil. This provides better protection against engine wear when compared to conventional oil but is definitely behind the full protection afforded by a fully synthetic. Usually, if a fully synthetic can afford your engine exceptional protection the moment you crank it up, a synthetic blend will require about 10 minutes of circulating before the engine can be well protected. However, when compared to conventional oils, semi-synthetics do a better job at reducing engine wear by as much as three times. When it comes to the frequency of oil change, it definitely is less frequent than conventional oil but is still a few oil changes behind fully synthetics.

The downside, of course, is that you don’t get all the amazing benefits of fully synthetics. On the bright side, it’s cheaper than fully synthetics and several miles better than conventional oils.

The most common SAE rating for semi synthetics include 5W-30, 10W-40, and 15W-40.

Conventional oil

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Well, this is the granddaddy of motor oils. The very first car engine that was bathed in conventional oil was the one fitted to the Ford Model T in 1908. You can just imagine the history of this type of engine lubricant. Modern conventional oils are produced by combining the base oils of hydrocarbons, polyinternal olefins, and polyalphaolefins. They usually come with SAE ratings 10W-40 and 15W-40.

This type of motor oil provides only the basic protection for most engines. It is definitely cheaper. Most new cars that are rolled out from the assembly line and be subjected to a break-in period also come with conventional oil. As such, it is often used in ‘seasoning’ the car engine before moving to semi-synthetics or even fully synthetics. It’s the ideal oil for people who have very ‘ordinary’ driving styles and who own cars with very simple engine designs.

Unfortunately, it doesn’t offer protection at extremely cold temperatures. It is also more susceptible to breakdown in excessive or extreme heat. You’d also need more frequent oil changes, typically every 3,000 or so miles.

Is it Okay to Use Diesel-Rated Engine Oils on Petrol Engines?

One of the most bugging questions many vehicle owners have is the interchangeability of motor oils. Can you use diesel-rated oils in gas engines? The answer may not be that simple.

First off, diesel engines have higher compression ratios than engines running on petrol and as such diesel engines tend to get very hot. Additionally, because of the high compression ratios and the nature of diesel fuel, more combustion byproducts are actually present requiring oils to typically have more detergents added in their formulation.

One more thing, diesel engine oils contain anti-foaming agents which are unique to these types of engines. Given that diesel-rated engine oils have higher SAE ratings and contain more additives such as anti-foaming agents and detergents, things that petrol engines don’t need, it is safe to say that you should never put diesel rated oils into your gas engine.

Well, here’s the thing. If the automotive industry did not do its part in moving forward especially in the fabrication of better-responding oils, then the answer is a straight ‘no’; you cannot put diesel oil in a petrol engine.

However, many modern car engine oils are now formulated to comply with all the requirements of both petrol and diesel engines. This means that you can now pour a canister of your favorite diesel-rated oil into your gas engine.

But there’s a catch. It is imperative that you choose the correct diesel oil specification that is commensurate to its petrol counterpart.

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Engine Oil Shelf Life

Technically, engine oils have shelf lives of four to five years. However, as years pass, unused engine oils can become obsolete and fail to meet the technical requirements of current engines. The specs get updated regularly based on new scientific testing procedures and engine requirements. But this is only really a concern for owners of brand new cars who still have engine oil bought for the previous car. An oil that is a number of years old might not be formulated to meet the requirements set for the newer engine.

If an unopened container of engine oil is more than three years old, read the labels to make sure they meet the latest industry standards. If they do meet the current standards, it’s wise to take the extra precaution of obtaining oil analysis before using them. An oil analysis will check for key properties of the oil and ensure that it still meets the original manufacturing specs. Of course the cost of getting an analysis done on old oil is probably going to outweigh going and buying fresh stuff. So it’s a double-edged sword.

As a general rule, the simpler the oil formulation, the longer the shelf life. The following is a guideline under protected conditions – indoors at about 20°C:

A Word about Engine Oil Additives

If you look in the market today, there are a lot of products that claim optimum performance for your engine. Many of these can be poured directly into your engine or even in the fuel tank. The point is that reputable engine oils are already tested to bring out the best in your engine. Adding chemicals into the oil can adversely affect the overall performance of the oil, so it is always best to make sure you choose the right type of oil additive for your vehicle.

The engine oil is your car engine’s lifeblood. It is thus crucial to choose the right kind of oil to pour into your engine.


  1. Engine oil – my car dictionary
  2. 5 Things Every Driver Should Know About Engine Oil – howstuffworks
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