Although oil has improved vastly over the past century, it is still extremely important that you use the correct type of oil and grade of oil for you engine / gearbox and for the use your car gets. Here I will explain some useful facts to help people understand why to use quality oil like Shell Helix or manufacture recommended oil, e.g Toyota recommends… etc
The functions and Properties of Oils
Oil is needed in engines and gearboxes as there is many metal moving parts inside of them that slide or rotate against each other, the main point is that the come in to contact or close contact with each other and cause friction and wear.
Without any means of protecting the parts or separating them, they would soon seize up or wear to the point of becoming out of use. Using a lubricant such as oil between them creates a protective barrier between moving parts which reduces friction and wear while also removing some level of heat as well.
A great amount of heat is generated in an internal combustion engine, as part of the purpose of lubrication is to carry the heat away from the moving parts and dissipate it in to the outside air. This feature is enhanced by an additional oil cooler you will sometimes notice (commonly around the oil filter, but not always) that is in a constant flow of air to then carry the heat from the oil out in to the air. In an engine (and automatic gearboxes) the oil is constantly pumped round the engine to ease movement of parts and ensure oil is always circulating through the oil filter and the rest of the oil system.
The oil filter filters out any small parts of metal or dirt in the oil to stop them clogging up oil ways or causing damage to internal parts, this can become full of dirt itself which is why it is important to periodically change this filter and the oil.
Oil is not simply just oil. It is made up of roughly 75-90% base oil, usually conventional or synthetic oil, and then 10-25% is made from additives. These additives will change depending on what brand oil you choose, which is one reason that it is important to choose quality brands, which we will get on to later.
The way oil is now made allows it to have the viscosity rating of one grade when cold but another grade when hot. ( e.g SAE 5W-30. This has a viscosity rating of 5 when cold – W is for winter – and 30 when the engine is at operating temperature.) This oil will still be thinner when it is hotter, but not as thin as a single grade oil would be, the example previous will act like a 30 grade oil when hot – so will be as thin as a 30 grade that is hot, this is slightly thinner in comparison to a 5 grade that is cold, but a lot thicker than a 5 grade that is hot, while also acting like a 5 grade only when cold. Hard to understand but I hope I got the point across, if you’re still confused, feel free to ask me a question at the bottom.
This multi-grade oil has a large benefit as most damage inside your engine is caused at a cold start, if the oil is thick then it will take a longer time to be pulled through the oil pump, along the oil galleries and in to the bearings or wherever it needs to be. So ideally you don’t want a thick oil to start your engine on as more damage will take place as the moving parts will not have enough lubrication for a longer amount of time.
Then once the engine is hot and therefor the oil is hot, you don’t want that same oil to of became even thinner (heat making oil less viscous) as it will be pushed out of the bearings and surfaces too easy. The multi-grade oil suits this as it changes how it acts in terms of viscosity to allow a balance of limited damage during a cold start while retaining enough viscosity to properly lubricate parts while hot. Overall this means less damage and your engine will last much longer!
Difference in Different Brand fuels
As mentioned previously, oil is typically made up of 75-90% of the base oil (conventional or synthetic) then 10-25% additives. These additives make a big difference in how long the oil can last, cleaning, cooling and lubrication properties.
Blow-by is where gases escape the combustion chamber past the piston rings and into the crank case and in to the oil, most of this is vented out again but is just one example of how oil can become sludgy when is mixed with the gases, this along with other dirt that can enter an engine over time can degrade the oil. These additives can help suspend carbon or other particles in the oil so when the oil is drained and renewed, they are also drained out the engine.
The better the additives, the better this works. Using Total, Castrol, Shell, Mobil, Penzoil etc oils all claim to do this well whereas some cheaper alternatives may not work quite as well.
What Oil Should I Use?
Almost always you should use the manufacturers specified grade oil, this is because the pump for the oil only creates movement of the oil, the actual oil pressure is from the resistance provided by the oil galleries and bearings etc, this resistance changes with different grade oils, with running a different oil pressure you may not be providing enough / or too much pressure for the internal parts and they could cause metal parts to rub against each other and where or cause seals to leak. Other than heavily modified engines, race engines, or extremely worn engines its best to use what the manufacturer specifies.
If you are one of the Toyota MR2 mk2 owners reading, Toyota recommends 10w-40. Toyota own brand or Shell helix seems to be the most recommended out there. Hopefully soon I shall have links in place of where they can be bought. (Boom! Now i do and have wrote them below, just click on them to take you to Amazon)
>>> Shell Helix Oil here <<<
>>> Genuine Toyota Oil here <<<
If anyone has any questions regarding oil please feel free to ask, even on any car 🙂