Semi Synthetic Engine Oil vs. Mineral Engine Oil

Synthetic Oil Explained

Whether it's evil stuff or good stuff depends on who you talk to. And a lot of what you hear from backyard mechanics are rumors and myths.

Myth # 1

The claim that you don't have to change Synthetic oil as often as regular motor oil. Remember when Mobil 1 said you could go 25,000 miles between oil changes with synthetic oil? Notice they haven't said that for a good number of years? Keep that thought on the back burner for now...

Myth #2

That synthetic oil causes oil leaks. In this article I'm going to try to dispell these myths for you with the cold hard facts about the differences and similarities between mineral vs. synthetic oil.

Let's talk first about what "mineral" oil. Mineral oil is created from something called "Base Stock". Base stock what the oil companies get after they have processed the crude oil that comes from the ground. From there, additives are combined with the Base Stock, to create our motor oil. There are 7 main additives which include anti-foaming agents, anti-corrosion, etc, etc. At the molecular level, mineral oil contains molecules of varying sizes. Imagine the floor of a gymnasium covered with basketballs, baseballs, volleyballs, and beach balls. Now imagine that all those different size "balls" are moving around, flowing past the floor. Every time a ball surface contacts the floor surface, the ball absorbs heat from the floor. That is how oil removes heat from your engine components, from surface to surface contact.

Now imagine the same gymnasium floor covered in uniformly sized golf balls. Smaller, more uniform molecules can absorb more heat from a surface, because there are more of them AND they have a larger surface to volume ratio which means they have more surface area contact. That's what synthetic oil is. A man-made "Base Stock", where all the molecules are the same size, and smaller than those in mineral oil. Better heat transfer, better lubricating properties, and a lot wider temperature range without breakdown, are now obtained.

Myth #1 debunked

Oil does not break down under normal use. This is true of both mineral and synthetic oil and is also the reason why you take oil to the Recycling Center and not the trash dump. So if oil itself doesn't ever degrade, why do we have to change it? The answer is twofold: additives and contamination. It will probably surprise you to learn that synthetic oil has all the same additives that mineral oil has! The additives in oil DO break down, which is part of what necessitates oil changes. The other reason for regular oil changes is that with use, motor oil becomes contaminated (dirt, water, acids, etc). Using synthetic oil does not protect against either of these problems, which is why you CANNOT go further between oil changes when running a synthetic. You should still change your synthetic oil at the same intervals as you do with mineral oil. Anyone want to guess how many claims Mobil 1 had to pay to people that were going 25,000 miles between changes?

Myth #2 debunked

Synthetic oil causing oil leaks is another commonly spread myth. The truth of the matter is that if all your engine seals and gaskets are in good condition, synthetic oil will NOT leak in your engine. The myth started because on occasion, an engine will leak with synthetic oil, but not mineral oil. The reason for this is that the smaller molecules of the synthetic are able to get past very small crevices, where the larger molecules of mineral oil cannot. But this does not mean that the synthetic oil has caused the leak, it simply has "discovered" an infant leak, and regardless of what oil you are running, this infant leak will eventually grow to a size that will allow dino oil to occupy and pass also. Synthetic oil has not been shown to deteriorate engine seals or gaskets. It is not some evil solvent that will break down sealant, or anything like that. Like was said earlier, it is just a man-made base stock, that is uniform and smaller in molecule size than mineral oil. Nothing more, nothing less.

ADVANTAGES OF RUNNING SYNTHETIC OIL

So if you are asking yourself "What's the point of running synthetic oil, if you can't change it less often?" Here's your answer in a nutshell.

Since synthetic oil has better heat transfer qualities than mineral oil, your internal engine temperatures will be lower. Things like bearings, especially, will not operate at as high of a temperature as a result. With head temperatures normally between 300-350 degrees, synthetic will not breakdown while lubricating the valvetrain components at the heads. The better lubricating properties of synthetic in general will lead to a longer engine life as well. On average, when synthetic oil is run in our engine, head temperatures stay the same, but engine oil temps reduce by anywhere from 10 to 15 degrees. This is in engines that have all the correct cooling tin in place, and are not suffering from overheating to begin with.

Important note: Do not run synthetic to fix a hot running engine. Find the real reason it's running hot, and fix it!

Another benefit is that since synthetic oil is man-made, it can be tailored to suit a wider range of needs. Synthetic oil is now being made is such weights as 5w50, and 0w30, weights that are not possible to achieve with mineral oils.

Another issue is whether to go for fully synthetic or semi-synthetic?

It really depend on your need. If you are running a daily driven family car, you do not need to use fully synthetic as your engine will not fully utilise its functions. It will be a totally different story if you are running a high performance engine.. So why waste when you don't need it.

We would recommend that you use semi-synthetic for average family car with engine capacity of 2.0cc & below. For high performance engine with capacity above 2.0 or with turbo, go for fully synthetic. DO NOT use the engine oil for too long. Try to make an effort to change it every 5,000km or 3 months whichever come first. This will save you valuable time & $$ in long run.

Beware of used or recycled engine oil! On average, mineral oil price from RM 40-RM 70, Semi Synthetic Price from RM 80-RM 140 & Fully Synthetic price from RM 160 onwards.