Synthetic vs Conventional Oil - There's A Good Reason To Switch

hello everyone and welcome in this video we are continuing this series sponsored by mobile one where they have provided me with access to their engineers to answer the many questions surrounding motor oils in this video in particular we're going to be looking at the differences between conventional and synthetic oils talking about what those differences are and what some of the advantages of a synthetic oil are so the first thing we're going to be looking at is viscosity index and viscosity index is simply looking at how viscosity changes with temperature so something with a low viscosity index changes a lot with temperature versus something with a high viscosity index which is good doesn't change as much depending on the temperature and so if you look at the base oil if you look at the molecules that make up the base oil of a conventional versus a synthetic what you'll notice is that a conventional oil has a lot of different varying size shape weight of the molecules that make it up and this in turn results in a low viscosity index so if you look at you know the molecules that make it up and no they're not you know circles and squares and triangles is just a simplified drawing but if you look at the molecules that make it up you'll have many large molecules and at low temperatures these large molecules prevent that flow and so that causes it to be thicker but you also have many very small molecules and so as you get to higher temperatures the abundance of all these very small molecules means that oil thins out a lot and so you have this low viscosity index where you have a dramatic change in viscosity as you change the temperature versus a synthetic oil which has that much more uniform structure again simplified drying here but it's undergone you know additional chemical processes they may use different chemicals uh different base oils to make it up and and so with this more uniform structure you have a higher viscosity index meaning you have less change with temperature and so what happens is at lower temperatures you have better flow because it doesn't thicken quite as much as a conventional oil and then at higher temperatures you have a thicker oil because it doesn't thin out as much like a conventional base oil and so with a thicker oil at higher temperatures you can have better wear protection now does that mean that you can't have similar curves for a conventional or synthetic oil no you can change these curves using additives but the bulk of what makes up a motor oil is the base oil and the base oil and the synthetic will have better characteristics as far as its viscosity index moving on to volatility of course you want your engine oil to remain a liquid now the challenge is that as you heat that oil up you can have some of it evaporate and you can lose that oil whether it's through the pcv system or burning through the engine you can lose that oil and so you want to make sure that oil remains a liquid and so there is a test and industry standardized test called the noac volatility test where you heat up some oil to 250 degrees for one hour and you have air flow passing over that to capture anything that's evaporating off from the oil and then you measure the mass loss after that one hour test and so the challenge with conventional oils if we go back to you know that uniform shape that makes up synthetics versus the varying size of conventionals because they have so many very small and you know molecules within it that lighter end is much more susceptible to evaporating off so what starts to happen well as you start to lose that lighter end you're left behind with the heavier larger molecules and so what happens is this starts to reduce your cold flow so now your cold flow is even worse as the viscosity increases further as you decrease in temperature so not a good thing to happen and with synthetics basically you're just slowing this effect because not as much is going to be burning off as you have you know that oil at higher temperatures now if you look at the back of a bottle of oil you can see what industry certifications the oil has and so if you see ilsac gf6 well this means it was able to pass the noack volatility test and it did not lose more than 15 percent of its mass through this volatility test now there are other tests for synthetic 15 isn't all that challenging it could be for some conventionals but there are other tests on here and so other tests like gm dexos 1 this can have a more strict requirement of 13 rather than 15 of your mass loss through this noack volatility test and so that can actually be challenging for some conventional oils out there ultimately synthetics tend to do much better in volatility tests due to having that much more uniform structure and not all of these very small light molecules now i mentioned earlier that you can use additives to change this viscosity index of the overall oil and so let's say you're trying to create a 5w30 oil and so to thicken the oil you're going to use viscosity modifiers now with a synthetic oil your starting point because that base oil has a higher viscosity index your starting point your starting viscosity at the high temperature end is higher and so if you're using viscosity modifiers which you add to help thicken that oil on the hot end if you're using those viscosity modifiers you'll need fewer viscosity modifiers for a synthetic base oil than for a conventional oil so for the conventional oil your starting point may be down here so you need a lot of viscosity modifiers to get it up to that desired whatever that desired oil weight is versus your synthetic here you're going to need less now why is that important ultimately you're going to have a similar shape at the end right at that temperature yes you can get them all to line up however viscosity modifiers are very large molecules in fact they can be about 200 to 2 000 times the size of the molecules that are making up your base oil so these very large molecules they're susceptible to creating deposits and an area where that can happen as the top of your piston so your top piston ring this is going to be a very hot area and so you can have these viscosity modifiers which are these very large molecules they can start to form deposits around your piston rings and eventually if you know you don't change your oil frequently enough the challenge you can have here is these deposits can then start to cause your piston rings to lock in place and so once your piston ring isn't moving anymore well you've lost your oil control you're going to have blow-by you're going to have cylinder damage because that locked piston ring can start to have deposits that are then scoring that cylinder wall and so basically the stuff that's above your combustion is then able to pass below and the stuff that's below your oil is able to come up into your combustion chamber so it just starts this really bad chain reaction of kind of just destroying your engine and so because synthetics use fewer viscosity modifiers they're less susceptible to having those deposits form in these you know high temperature areas where you can have damage occur from that of course another trend within the industry is moving towards small turbocharged engines and so these small turbocharged engines have areas of very high heat concentration a lot of heat in a smaller area and so while they may all be rated for the same viscosity at one temperature as you extend these curves out what happens is because that synthetic oil has a better base oil that doesn't thin out quite as much with temperature as you extend these curves the synthetic actually remains thicker and so it's able to better protect the engine at higher temperatures finally we get to oxidation so this is when oxygen reacts with the oil and starts to change it so you know if you leave your car out in the rain you can look at the brake rotors the next day and you might see that some rust has built up on those rotors that's oxidation oxygen reacting with those brake rotors and you know a similar thing happens with motor oil oxygen will react with it and change it and so this will actually start to form sludge and increase the molecular weight of the molecules within oil and so it'll start to get really thick and then you have to change the oil and so heat accelerates this process of oxidation and so if you look at a conventional base oil one of the things you'll find is that it will have more unsaturated molecules so this is kind of getting into the chemistry of it why this oxidation actually occurs and so these unsaturated molecules they have ring structures and they have double bonds and so what happens is these are susceptible once you get into higher temperatures of oxygen coming in and messing up these molecules and so oxygen will come along and it will attach to these molecules and it will start to grow the molecule and so once that you know oxygen has come on it'll start to get more attachments and more and more and a chain reaction just starts to occur and it just creates all these new species and they grow in weight and size and that gets your oil really thick and hence you have an oil drain interval you need to change it out before this starts to get really bad and so the challenge with conventionals is that they're susceptible to this oxidation and so with this synthetic base oil what you do is you use saturated molecules which don't have ring structures they don't have double bonds and so these are very stable molecules and it's much more difficult for oxygen to come get involved and start messing everything up and so there's really two strategies you can use with oxidation it's inevitable it's going to occur regardless but you use stable base oils and then you can use additives antioxidant additives to slow the process so ultimately you can prolong it using synthetic base oils and using antioxidant additives but it will happen eventually and so eventually you do have to change out that oil but using this strategy you're able to use longer drain intervals so hopefully this has been insightful into some of the differences between a synthetic and a conventional oil and some of the advantages that synthetic oils have thank you to mobile one for sponsoring this video thank you all so much for watching and if you have any questions or comments feel free to leave them below

Channel: Engineering Explained

Views: 456,680

Keywords: synthetic vs conventional, synthetic oil, synthetic motor oil, motor oil, mobil 1, mobil 1 synthetic, high mileage oil, engineering explained, full synthetic, is mobil 1 synthetic, conventional oil, oil drain interval, when should you change oil

Id: lo7rrex0IsE

Length: 10min 16sec (616 seconds)

Published: Wed Dec 16 2020