Will Thinner Oils Damage Your Engine?

hello everyone and welcome in this video sponsored by mobil1 they have provided me with access to their engineering teams so we're going to be focusing on three questions about motor oils what do oil weights actually mean do thinner oils improve fuel efficiency and can thin oils effectively protect an engine now beside me is a cutaway of the 6.2 liter v8 engine that is found inside the c8 corvette this engine is factory filled with mobile one and i'm going to be using it as an aid and explaining how oil interacts with your engine so let's start off with oil weights and what these numbers really mean now right off the bat we need to clarify something the term weight isn't all that appropriate to use as these numbers don't represent a weight measurement but rather a viscosity measurement so what these numbers really identify is the oil's viscosity grade viscosity is essentially the fluid's thickness a thicker fluid like honey will have a higher viscosity than a thinner fluid like water ensuring the proper viscosity is the single most important criterion of a motor oil and the higher the viscosity grade on the bottle the thicker the oil but these numbers are also temperature dependent so for example here we have a 10 w30 oil the first number 10w w standing for winter represents this oil's viscosity grade when it is cold the second number 30 represents the oil's viscosity grade when it's hot because there are two different numbers here this is called a multi-grade oil now since the second number is larger than the first number does this mean this oil gets thicker as it heats up well no it just means it behaves like a thicker grade oil in sae 30 grade when it's hot but it behaves like an sae 10 grade when it's cold here's a quick demonstration so in this cylinder i have 100 milliliters of 5w30 at room temperature and then in this cylinder i have 100 milliliters of that same exact oil 5w30 except it's been sitting in the freezer overnight so i'm going to drop a ball bearing into each cylinder and whichever one hits the bottom first that's the thinner fluid i expect this is going to be messy ready beautiful as you can see the cold cylinder here with the cold 5w30 took significantly longer for that ball to reach the bottom so as oil heats up its viscosity decreases if you look at a graph of temperature versus viscosity it will look something like this so in blue we have a 0w40 oil like what's found in the corvette and then our red line is a 10w30 and so what you'll see is at cold temperatures the 10w30 is thicker however as that oil reaches operating temperatures the 0w40 is thicker and both oils continue to get thinner as they increase in temperature so how does an oil behave like different grades depending on temperature well typically you start with a low viscosity base oil and then you use additives specifically viscosity modifiers to change that rating as the oil heats up now let's go back to our 5w30 oil and talk about how it gets classified as a 5w30 both of these numbers have multiple tests at multiple temperatures to certify the rating the cold rating includes tests that range from negative 10 degrees celsius to negative 40 degrees celsius and in these cold temperatures you're looking for two things first can the engine actually start so back when cars used carburetors and distributors you needed a fairly high cranking speed to actually start the engine if the oil was too cold it could prevent the crankshaft from spinning fast enough and genuinely prevent you from starting the car now modern cars with fuel injection can start at lower cranking speeds but you still need to make sure the oil is thin enough to be picked up by the oil pump and circulated through the engine so the second part if the car starts you need to ensure the oil actually flows if the oil gets too cold it can start to have wax crystals formed and it starts to form a structure rather than acting like a fluid obviously if you don't have oil flow you're not protecting your engine so it's critical to have a test that ensures at low temperatures the oil doesn't get too thick now the second part of the rating 30 is based on viscosity measurements taken at 100 and 150 degrees celsius in these high temperature tests we're looking at the oil flow as it relates to seal leakage which can impact oil consumption and we're looking at the viscosity of our oil when it's forced into a very thin oil film like with bearings the piston cylinder interaction and camshafts now as far as what contributes overall to the viscosity rating and it's of course dependent on what this rating is but generally speaking the cold rating is more dependent on the base oil that is used and then the hot rating is going to be dependent on the additives like viscosity modifiers now perhaps you've noticed a trend in the automotive industry in that these numbers keep getting lower and lower and in fact there are production cars sold today with zero w16 engine oils so why are they doing this well generally speaking the lower these numbers are the better your engine efficiency is and this is an industry where efficiency is everything now can they still protect at the same levels as thicker oils we'll tackle that question a little later on in this video so why are thinner oils more efficient well basically it comes down to friction if you think about dragging your hand across a surface of honey it's slow and it's difficult to do if you think about dragging your hand across the surface of water well it's easier and it takes less energy to do so the same idea applies to oils which act as a protective barrier between two surfaces but of course you still have friction between the metal surface and the oil the question is how much can you actually increase efficiency by with the obvious disclaimer that it depends on many things like which viscosity grade we're comparing versus another what engine we're using what the operating conditions are and so on but i've seen studies showing that going from a 30 to a 20 could result in over a 1 increase in efficiency as well as going from a 20 to a 10. if you look at fuel economy testing lower viscosity grades are required to meet more challenging fuel economy limits because it's known that they improve efficiency based on these fuel economy tests you can derive the benefit of a 0w or 5w20 over a 5w or 0w30 is in the 0.3 percent to 0.5 percent range and the benefit of a 0w or a 5w30 over a 10w 30 is in the 0.2 to 0.7 range now fighting for a fraction of a percentage improvement in fuel economy may not sound significant for those who aren't working within the field of internal combustion efficiency but when you consider how efficient today's engines are gas engines with peak efficiency around 40 percent raising that number to 41 is a very difficult problem to solve and oil can help play a role in solving that i understand that fuel efficiency isn't everyone's favorite subject but i have to admire the very challenging problem engineers are faced with and the solutions that result from tackling this problem so the big question can thinner motor oils effectively protect an engine and i've asked this question to a fair number of powertrain engineers and i discussed it with mobil1 and with modern engines engine wear is usually not a limiting factor companies have done an extremely good job of figuring out how to make the internals of engines last what's more challenging is improving fuel economy and since you can do this by moving to thinner oils companies are doing it i think it's worth understanding how wear happens so that you can better realize how thinner oils can still protect engines from wear as long as you're using the oil that your engine is designed for which you'll find in your owner's manual and we'll get into a few exceptions engines really don't have metal on metal contact you simply have oil between the moving metal surfaces and as long as your oil pump is maintaining proper flow and your oil is in good shape and being changed at regular intervals you won't have much metal wear now there are instances like when you start up the car that you won't have that full oil film thickness between the moving parts available that's when anti-wear additives are useful that stick to metal surfaces and minimize wear at startup there's also something very interesting that happens with your pistons and cylinder walls so you have oil sprayers that are coating these walls to protect this piston as it moves up and down and as long as that piston is moving it's protected by that barrier that film of oil however the piston isn't always moving so when it reaches the very top it switches directions and so for a brief moment the piston is stopped and then when it reaches the very bottom again it changes direction so for a very brief moment it's not moving as an analogy think about a person sitting on water skis in about a foot of water so if that person's not moving well then their water skis are resting on the sand below them beneath that foot of water but once the boat starts to pull them those water skis pop up on top of the surface water doesn't have a super high viscosity but even still when your velocity goes up you pop up on top of that water and within your engine once that piston starts moving up or down again it pops up onto that oil film for the vast majority of your engine you have a high velocity between moving metal parts and that high velocity keeps the parts floating on an oil film preventing wear now does that mean you should simply go out buy a thinner oil and stick it in your car no your engine was designed and validated using a specific oil verifying that the engine had an acceptable life and durability desired fuel economy and met an acceptable oil drain interval you should always always always did i say always enough use what's recommended in your owner's manual but let's have fun with some hypotheticals which again you should absolutely not do this engine uses mobile ones zero w40 so what if you put 0w20 in it well that would probably be bad higher performance engines will see higher loads on the engine parts and may need that higher viscosity for a more robust oil film you might have too much leakage in the journal bearings if you used a thin oil so as a general rule going lower on the hot rating number is a bad idea but what if you went thicker with the hot rating well generally speaking it's not terrible though again not recommended in specific cases where a car sees a lot of track time and the oils are getting into much higher temperatures sometimes you'll see cars recommend thicker viscosity grades when you're on the track to make sure the viscosity is still high enough at those higher temperatures now what if you went lower with the first number so say your car recommends a 10 w30 and instead you put a 5w30 in it well if you look at the overall viscosity range of each of these different oil grades you'll see that the 5w30 range falls entirely within the 10w30 range so really the engine wouldn't be seeing a viscosity that it hasn't seen before but if you went the opposite direction say your car recommends a 5w30 and you put a 10w30 in it well then at cold temperatures it's going to be seeing a much thicker oil and so you could run into cold cranking and oil pumping problems so the definitive rule use what the manufacturer recommends if you use a higher number here or a lower number here bad things can happen if you use a lower number here or a higher number here it's not as risky have i said it enough times how many times have i said it use what your car manufacturer recommends hopefully we've all learned a thing or two about oil and how cool is this engine cutaway 6.2 liter naturally aspirated v8 engine 495 horsepower 470 pound-feet of torque dry sump oil system cylinder deactivation equal length intake runners swept up exhaust manifold it's a very cool engine sounds phenomenal and it's a joy to drive a big thank you to mobile one for sponsoring this video and providing access to their engineering teams check out the link in my video description to find mobile one at an auto zone near you thank you all so much for watching if you have any questions or comments feel free to leave them below

Channel: Engineering Explained

Views: 1,282,370

Rating: 4.9144344 out of 5

Keywords: motor oil, engine oil, mobil 1, 0W-20, 5W-20, 5W-30, 0W-30, are 0W oils safe, best motor oil, best engine oil, best, top motor oil, mobil 1 motor oil, mobil 1 synthetic, mobil 1 full synthetic, mobil 1 annual protection, 20000 miles, 20000 mile oil change, oil myths, oil weight, oil efficiency, efficiency, engines, turbocharged engined, corvette engine, c8 engine, 2020 corvette, 2021 corvette engine, thin motor oil, 0W-20 too thin

Id: IKdhgKUZhPA

Length: 12min 39sec (759 seconds)

Published: Wed Jul 29 2020