Will Thinner Oils Damage Your Engine?

Published 2020-07-29
Can thin motor oils protect your engine?
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What do oil weights mean? What does 5W-30 mean? Do thinner oils get better fuel economy? Do thin oils like 0W-20 protect your engine? I spent some time discussing these questions with Mobil 1 engineers and am excited to share what I learned. There’s an incredible amount of testing and verification that goes into labeling a motor oil’s viscosity rating, which is the single most important factor for how a motor oil will perform in an engine. Motor oil is responsible for protecting your engine, removing contaminants, reducing friction and cooling your engine. Plus, motor oil creates a protective barrier between moving metal parts allowing for your engine’s longevity. In this video we’ll use a 6.2L V8 engine cutaway from the C8 Corvette to better see and understand how oil interacts with automotive engines. #Mobil1Partner

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All Comments (21)
  • Clarification! There still seems to be confusion about the viscosity decreasing with heat, yet the number is higher, for example 5W-30.
    1. This is explained from about 1:05 to 3:05.
    2. All motor oils (basically) will decrease in viscosity as they heat up (become thinner).
    3. Motor oils will increase (become thicker) in viscosity as they cool (as demonstrated in the video with graduated cylinders).
    4. A 0W oil has a lower viscosity than a 10W oil when it is cold (the number is lower).
    5. A 40 grade oil is thicker than a 30 grade oil when it is hot.
    6. A 10W-30 (as shown at 2:28) will be thicker at cold temperatures, but thinner at high temperatures, versus a 0W-40.
    7. The rating is temperature dependent! There is a cold rating, and a hot rating, which comes from tests (shown at 3:17).
    8. Even though the number increases as it gets hot (like 5W-30), the viscosity decreases. It means the oil behaves like a 5 grade oil when cold, but a 30 grade oil when hot. How?
    9. Viscosity modifiers are molecules that expand as they heat up, which decreases how much thinner the oil gets as it heats up. It still gets thinner, but not as thin as it could get if the viscosity modifiers were not in there. This is what makes it a multi-grade oil. Because it behaves like different oil grades depending on temperature.
    10. In summary, a 5W-30 will decrease in viscosity as it is heated, however its hot rating is a thicker grade oil than its cold rating. See plots in video (2:28) to see what this looks like.
  • SomeWeeb
    As a Chemist, I can confirm that honey does have a higher viscosity than water.
  • Don Hendricks
    As an auto mechanic in years past, I still have a problem wrapping my thoughts around understand how quickly spark occurs in a cylinder versus fuel burn at high rpms.
  • GrandeTaco
    I liked the ball bearing test, I really would have liked to see the 0w version of the drop test though.
  • gidderman
    I have come across instances where running a higher grade oil in a higher milage or worn engine can be helpful. There is one scenerio in particular that i have experienced better results: A 2013 Ford Taurus 3.5L n/a that had over 120,000km on the engine, the engine showed signs of poor maitenance and increased wear internally (i had the engine covers off).
    After discussing it with the owner it was found that putting a large sum into the vehicle to rebuild the engine was not worth the value of the vehicle. A lower cost solution, a comprimise, was reached to go up from 5w20 factory oil grade to 5w30, and use a high-milage oil blend.
    After switching to this oil, fuel economy change was negligable, however the previously noisey engine had now quieted down remarkably. This vehicle now has an additional 60,000km on it and is still running excellent, and quiet. There are many tips and tricks you can utilize to extend the life of your vehicle, you just need to make application specific determinations as per your scenario.
    If you drive your car like you stole it everyday, high load, high stress conditions, then sometimes changing grades is worth it. Also if you have an older car, with high milage or high wear, changing grades can also be benificial, and if your warrenty is likely expired there is nothing stopping you from consulting good resources and making your own choice as to what grade you use.
  • Jim Nesta
    How well will the high temperature viscosity levels of these thin oils hold out after having been in the crankcase for 2K or more miles?
  • craig
    Thank you for doing all the footwork, EE. I have often wondered about these lubrication questions.
  • turbinepower77
    I'm an aircraft mechanic and I used to work in gas turbine engines.(jet engines) The synthetic oil used in those engines that reach 60 000 rpm was so thin you couldn't tell the difference between the oil and the jet fuel.
  • Gabriel Costa
    I live in a place where going below 5c is really rare and I tend to use 10w40 in my 5w40 rated car. I've been told that without actual cold climates the difference is minimal between their performance, but it's high in costs where I live.
  • Hugh Spencer
    Great video. Oils are indeed a very complex subject and I am not a chemist. My Indian Springfield motorcycle is a strange mix of old and new technology. Air cooled and semi dry sump lubrication. Indian specify a specific semi synthetic oil for lubrication. I have found that the engine really should not be worked hard until it's at full operating temperature because until it is at the correct temperature the flow rate characteristic mean that you cannot accurately measure the oil. By my thinking the engine is potentially not getting optimal lubrication until the correct temperature and hence viscosity is achieved. As I have owned the bike from new it has been treated with care until proper temperature is reached. Equally however as an air cooled engine there is a real risk of lubrication degradation at extreme temperatures. E.g. Death Valley in summer. This motorcycle is actually faced with quite difficult lubrication challenges because it is air cooled. Indian essentially detune the engine to improve reliability and essentially lubrication . But the really interesting thing to me is many motorcycle owners like to increase the power potential by changing components. But the one thing they don't change is the oil pump. And yet in a car engine improving performance generally includes an oil pump upgrade. You really want to hope that your oil is going to protect vital bearing surfaces. Cheers
  • njstorozuk
    Glad to see you've come this far. Great content still. I'm basically falling asleep at night to it because of my curiosity and I'm enjoying the education, regardless of me already working on my own car
  • Chad Boutchyard
    Love this channel. I hardly ever have further questions after watching any of his vids. He seems to answer what you may be thinking.
  • prawny12009
    10w-30 and straight 30w will be identical viscosity at operating temperature.

    This is one of the reasons old engines running mono grade oil needed warming up properly.
  • Paul Feasal
    In most cases its best to use what the manufacturer recommends. Until that vehicle gets over a 100 plus thousand miles. But remember its best to have a mechanic explain the pros and cons of changing the oil. It can also cause leaks in the seals and other issues. The friction will change as your vehicle ages.
  • Greg H
    The thinner recommended oil contributes to lifter/rocker arm bearing failure on Chrysler 3.6l pentastar engines. Earlier engines used thicker viscosity and did not suffer lifter failure at same rate. Pentastar tick is becoming very common.
  • Cool video ! Had an Audi Q5 3.2 v6 gas, took 0w-40, above average mpg for that much v6, ~ 23-24mpg. Now got '19 VW Tiguan AWD, takes 0W-20 and again I average way more than the stated mpg, 30+mpg. Awesome, I'll take it :D
  • Use 0/20 for the temps down to -40C and mobil 5/30 for summer in western Canada which so far seems to be working ok. L/100 seems fine on both.
  • Ray Parra
    If i had the chance to talk to an automotive engineer, i would like to asked them this question..."How come them have not fixed the common oil leak from an engine"
  • sptrader
    I just hope that going with lower viscosity oil to increase efficiency by 1%, is not causing 10% shorter engine life. I'd like to see data that proves that engine life isn't sacrificed at all.