Motor Oil Myths & FAQs – Synthetic vs Conventional

Hello everyone, and welcome. In this video, we’re going to be discussing frequently asked questions and myths surrounding motor oil. Now rather than me blabbering and trying to convince you of what is true. I’m going to be asking Shanna Simmons, who is a research engineer for Shell. Who has access to the information and research needed to answer these questions. And hopefully she can put some of these myths to rest. So my first question is, “I put 5W-30 in one of my cars. What does that combination of letters and numbers mean?” Let’s discuss what a multi-grade viscosity really means. So, the 5 is the viscosity grade when it is cold. So, remember the W stands for winter. The 30 is the viscosity grade at the engine’s operating temperature. Engines operate at around 212°F (100°C). Okay, so why should I change my oil? As an engine burns fuel it deteriorates the motor oil. Changing your oil helps to remove harmful contaminates and it replenishes the additives that have been depleted. So, what is the typical composition of motor oil? So this chart shows the typical composition of motor oil. So depending on the formulation, the motor oil will be about 75-90% base oil. The other 10-25% will be additives. So the base oil determines the fundamental properties of the motor oil and the additives help to enhance the base oil, help to protect the base oil and help to protect the mechanical equipment. Ok, now you mentioned oil additives. Are aftermarket oil additives something I should be using? No! Branded products already contain carefully balanced additives for optimal performance. And I’m sure that same logic can be applied to many brands of oil out there. Now, alot of people debate about conventional and synthetic oil. Before we get into that, what is the difference between these two terms? So the base oil can either be conventional or synthetic. If the base oil is conventional it means it’s only been refined from crude oil. If it is synthetic it means it has been through an additional chemically engineered process to give it better properties for use in a motor oil. Okay, so is synthetic oil compatible with conventional oil? And can the two be mixed? Yes. Motor oil labelled a synthetic blend already contains both synthetic and conventional base oil in the formulation. We also carefully test our motor oils with other motor oils to ensure compatibility. A lot of people debate whether or not you can use synthetic oil to break in an engine. Can you? Yes. In fact, a majority of vehicles manufactured today are factory filled with synthetic oil. And many race teams also use synthetic oils to break in their engines. Now, sludge is a term often brought up when talking about engines and oil, what is sludge and what causes it? So, every time your engine is running by-products from combustion build up and contaminate the motor oil. If contaminants build up inside your engine they can set a lot and form sludge. Using low-quality motor oil, neglecting to change your oil and maintenance issues can all lead to sludge forming inside your engine. Now I often get the question, can I use this certain viscosity grade even though the manufacturer suggests another viscosity grade? Why should I use the viscosity grade that the manufacturer recommends? Your engine was designed with the specific viscosity grade in order to lubricate menchanical parts properly. If you use oil that is too thin, you may run into wear issues. If the oil is too thick, engine efficiency may decrease. Always follow your vehicle’s owners manual to determine the correct SAE viscosity grade to use inside your engine. So, a huge thank you to Shanna for helping answer some of these questions and as always if you have any questions or comments feel free to leave them below. Thanks for watching.


  1. Pleindespoir said:

    Everybody knows that women can't have any idea about technical issues. How can you believe somebody who isn't able to get a small car in a parking lot?

    January 8, 2018
  2. Aaron Mears said:

    I hear all the time that older vehicles that have always used conventional oil should be kept with conventional oil. Is there any reason not to switch to synthetic on a 30 year-old car?

    January 15, 2018
  3. esa khan said:

    She was designed to do so

    January 15, 2018
  4. Callum Roper said:

    For engine upgrades, what is more important to change once power reaches a certain level (say, for example, a 1.8ltr NB MX5 when the engine power is doubled) to maintain effectiveness? Oil viscosity or oil cooling?

    January 16, 2018
  5. Chee Jun said:

    Thumbs up !

    January 24, 2018
  6. Muhammad Zeeshan Aijaz said:

    Hi. Does manufacturer recommended oil viscosity have anything to do with ambient temperature of the location you drive your car?

    January 27, 2018
  7. up648 said:

    with that  being said what about for older vehicles which most mechanics seem to recommend using a higher viscosity oil for that vehicle say originally a vehicle is supposed to use 5w-20 but after 150K miles the mechanic recommends using 5W-30 would that still cause an engine deficiency issue or not?

    February 1, 2018
  8. Frog - Tech - Tips said:

    Thanks this qive me answer I looking for

    February 1, 2018
  9. Agam Kaushik said:

    I thought it was him in drag

    February 5, 2018
  10. Shajie Khan said:

    Ford recommends 5w-30 (preferred as per the owner's manual) for my car but 10w-40 (A5/B5 specs) is also an acceptable grade. I live in the desert where the temperatures rise up to 50degC (120degF). Do you think it is better to use 10w-40? or I should stick with 5w-30 as it is the manufacturer's preferred choice. The temperature never dives below 15degC (60degF). I am trying to understand the relation between the ambient temperature and the engine oil grade.

    February 7, 2018
  11. Seth Myers said:

    Pennzoil has paraffin wax…. don’t use it

    February 12, 2018
  12. Ed F said:

    If I have oil changes regularly, why would I need high mile oil past 75,000?

    February 18, 2018
  13. Gino Foogle said:

    dino oil is fine if you are a religious oil changer.. no need to waste extra money on marginal returns..

    February 20, 2018
  14. Ali Erikenoglu said:

    She didn't fully explain why synthetic is superior to conventional oil, did I miss something?

    February 24, 2018
  15. eduardo fuentes alcantara said:

    Thanks for the subtitles in Spanish excellent information

    February 25, 2018
  16. Pussaty said:

    She looks stoned…

    March 8, 2018
  17. Alcanobee One said:

    What about boron additives, are they worth it, do they really work that much better?

    March 9, 2018
  18. Audio said:

    Not changing your PCV valve on schedule can result in sludge.

    March 16, 2018
  19. MrMusic1950 said:

    All oils are exactly the same, they are oil and nothing else. Fools pay big, wise pay little.

    April 5, 2018
  20. Apurv Jadhav said:

    How winter is that w winter 🤔

    April 15, 2018
  21. Marco Rubio said:

    Good video! U clowns always trying to make excuses.

    April 19, 2018
  22. Dennis Cooper said:

    Nice helmet daawg.

    April 28, 2018
  23. finn bell said:

    love a lady with brains

    May 3, 2018
  24. The Beaten Paths said:

    Love how that "Shell oil expert" reads off the piece of paper she's holding. I use Amsoil, and don't worry about a thing. Oil companies like Shell don't make a good synthetic. Their bread & butter comes from crude and don't really want you buying Synthetics, so why would they make the best synthetics they could?

    May 17, 2018
  25. Myl Ra said:

    Why does she begin every sentence with the word so

    May 19, 2018
  26. Joe Lafleur said:

    So it seems if you were to use additives such as Lucus, this applies to those who use cheap oil within their oil changes. Another thing that I got was to change your oil& filter more often than not.

    May 20, 2018
  27. Nhat Tran said:

    Can synthetic SAE 5W-30 oil be used in place of manufacture recommended SAE 5W-30?

    May 23, 2018
  28. Racer X said:

    Shannon's hot!!!

    May 24, 2018
  29. Kevin Ho said:

    We are factory of motorcycle engine oil. If you want to wholesale , pls contact me on whatsapp +8618689280424

    May 28, 2018
  30. KS Lee said:

    This is basic information about synthetic oil, supplied by oil maker. Nothing more or less. Thanks!

    May 31, 2018
  31. Groom Lake said:

    Your almost sending people in a bad direction!!! Synthetic oil has lots of detergent to act as a dispersant . As filtration technology became better in the early 80s they started adding detergent to lock on to the particulate to make the mass of the combined material bigger so that the filter element could lock on to it and retain the contaminate removing it from the engine. Back in the day it was common practice to remove the oil pan and clean the contaminated sludge off the oil pan. Back then filtration was not that good so the used a straight weight non detergent oil so the contaminant would settle to the bottom. Now days the good stuff in oil like ZDDP aka zinc is being removed because it’s bad form the catalytic converts . This means oil company’s are more worried about O2 sensors and catalyst filters then the proper lubrication to the engine. It’s also VERY IMPORTANT to understand that detergent being a dispersant also means it will not allow the good stuff like zinc to adhere to the friction surfaces. This is why when breaking in a older flat tapped or even roller lifter engine it’s best to use a non detergent oil. By using a straight weight NON detergent oil and mixing the ZDDP zink additive to it will greatly help the break in period . To my knowledge except racing oils there are no straight viscosity synthetic oils that have low levels of detergent . To recap oil company’s and fuel company’s are more worried about emissions and mpg…than protecting engines . Honestly the 3 best oil brands you can run are… red line oil because the base oil they use is super high end and found in transformers on telephone pols used to cool. The red line oil resits burning considerably better than any thing else out there. This is very important in my line of work to combat the driver burning to death, but also is important in high performance engine with high cylinder pressures because of induced detonation due to oil getting in to the combustion chamber . Combustion technology’s aka Clean boost oil is right there with red line. The owner of clean boost was red lines head chemist for manny years. There’s also Mr Race Oil . A new company doing very great things in the high Perfromance field. I love your vids and your a smart kid. I think the older you get you will start to realize there’s a lot more out there to learn then first thought as a young man.

    June 11, 2018
  32. Groom Lake said:

    I will tell you that Joe Gibbs driven break in oil is worth it’s weight in gold In my book. Brad Pen is also. There was a lot of nitro engines scuffing pistons on the warm up. By just switching oils to the redline nitro 70 weight all that went away. In my personal Diesel trucks I run nothing but Rotella . I have friends that run mini mod tractors with blow alky hemis that are sponsored by shell. The new race oil shell came out with is pretty unreal how good it is.

    June 11, 2018
  33. Google User said:

    ALL multi viscosity oils are a COMPROMISE regardless of type or brand………..And the wider the range, the worse the oil is due to all the additives used to try and immitate a straight weight oil………..

    June 13, 2018
  34. Teo Picado said:

    Mmm and lets say a car says use 5-30 but after 200k should still use 5w-30?

    June 19, 2018
  35. David Nixon said:

    Pennzoil is Shell with different branding for the US market. It is not considered a top tier oil here in the UK….. I will be staying with Petro- Canada Supreme Synthetic.

    June 19, 2018
  36. Tr1ckySureShot said:

    She's bomb, she can change my oil anytime.

    June 27, 2018
  37. Google User said:

    There is no one size fits all motor oil……….As always, the type and viscosity of the oil you need to use varies wildly from one region to another and from one driver to another………The 0w-20 and 5w-20 oils stamped on the oil cap are merely CAFE compliant oils that should only be used if you live in the arctic circle……..Everybody else needs to use 5w-30 or or greater viscosities……..And those living in hot southern climates need to use a 10w-30 or 10w-40……….

    July 2, 2018
  38. Groom Lake said:

    Red line or Clean boost oil is the absolute best. All you have to do it try to clean it. Spraying break cleaner at it is like water. Only race gas will break it down

    July 5, 2018
  39. Bruce Guillaume said:

    Does a diesel engine's oil break down less or none whatsoever over time due to its fuel being an oil versus gasoline is more like a solvent? Or is it due to diesels somehow having a tighter piston ring seal preventing fuel from entering crankcase and breaking down the oil. I've heard thats a major contributor to the longevity of a diesel engine. (other than lower engine operating speeds and block rigidity)

    July 9, 2018
  40. Janine McLaren said:

    If I mix 5w30 Amsoil with 5w50 Amsoil in equal amounts, will I get a 5w40 viscosity rating? No one on YouTube has addressed this issue, that I can find.

    July 30, 2018
  41. Jhonathan Rivera said:

    OK… Now so since the first number is for winter viscosity… and since the other number is the viscosity at operating temperature, If I am doing an oil change during the summer and I know I will changing my oil soon again (long trip planned) could I use a 10w40 instead of a 5w40? They are both 40 at the running temperature…

    August 1, 2018
  42. Daffy Dill said:

    Synthetic oil was designed for people who go past regular conventional oil changes. It's recommended to change oil at 3000-5000 miles where synthetic can last about 2000 longer. Conventional oil is just as good as synthetic oil as long as your religious with your oil changes. Conventional oil has been used since the automobile and has done well since then. Keep your oil changed using conventional oil and you will not have any problems.

    August 5, 2018
  43. Qk9CWU5ib3x said:

    This is best channel to geek out on Car engine!!!!!!!

    August 18, 2018
  44. Leon Holomon said:

    What if your engine has miles on and you want to put a heavier weight oil

    August 18, 2018
  45. Recco Con said:

    You think l could use viscosity oils in my lawnmower? They suggested straight sae 30? Why not a thinner 5w or 10 w ?

    August 27, 2018
  46. RYAN SEACREST said:


    August 31, 2018
  47. tbillyjoeroth said:

    The missing thing was: how can an oil possibly be thinner when it's colder????? Makes no sense.

    September 1, 2018
  48. kiyonexus said:

    This is the most horrible editing combination ever… The guy sounds like he's in a closet and the girl footage is clearly another video the dude just recorded playing back on a screen… Both horrible.

    September 8, 2018
  49. doctor jones said:

    Hello mr.boney arms👋😃 i thought i had boney arms😕❗i guess i can start wearing t-shirts again😏👍

    September 24, 2018
  50. Major Dick said:

    Your Aunt seems nice.


    After the commercial at the end he revels that was him in a wig… Mind blown.

    September 25, 2018
  51. Jose C said:

    What about ester oil ? Do cars really need it ? For example, my service advisor just told me my 2016 Maxima SR requires ester

    September 28, 2018
  52. علي ال عجه said:

    No woman no cry

    September 29, 2018
  53. BigDaddyJinx said:

    Did she seriously just say "W stands for winter"?


    Weight. It stands for weight. WOW.

    October 8, 2018
  54. jon lipton said:

    Should I ever use engine oil adaptives? “No!” Boi I’ve been using Lucas oil in my ford since day 1 and it’s been the best investment of 8 bucks I’ve ever gotten

    October 9, 2018
  55. Nicholas Vonrhine said:

    I can say this some oils make my old engine really quiet and others don't.

    October 10, 2018
  56. Filippo Cunsolo said:

    So 10w 40 motercly oil I put in my 49cc SCOOTER. Will not work anymore.

    October 11, 2018
  57. Vidde H said:

    Usual Oil Additives in Europe is 10.6-13.7% and the USA has 5-7% Additives. Same oil can be of different quality in EU and USA market bc ACEA and API cant be compared directly. No International/worldwide classification exists. Here in EU we say that oil in API group III is "partly synthetic" and group IV (PAO) is ""fully synthetic" and oc group I and II is mineral oil. In the USA group III oil is often called ""fully synthetic" incorrectly.

    October 17, 2018
  58. Corona light said:

    Good video

    October 23, 2018
  59. Anonymike said:

    2i2 degrees fahrenhite. Boiling hot. Steaming.

    November 3, 2018
  60. KR P said:

    In 5W 30 , 5 is a viscosity reference at cold temp but at what temp ? 30 is actually a SAE30 again a number on viscosity chart at 212 F. When oil gets heated up usually they tend to become thin and viscosity decreases, but still we read 30 which is way more than 5 at cold condition. How will you explain that ? Viscosity is a viscosity ….whether cold condition or hot. Does it mean viscosity number chart is different for cold and hot condition ? There are so many videos where product seller is trying to show through pour test at – (minus) 10 or 20 C where the oil looks so thick and hence is must be high but yet number given is only 5. How do you explain that ? When oil gets heat up at 212 F it becomes 30 ? …..if 5 is so thick then what will be 30 ? Pls explain the logic behind it …..

    November 3, 2018
  61. Endranse Kuhn said:

    I switched to a 5w 40 synthetic oil in my 97 daweoo lanos without experiencing any kind of leaks will it harm my engine? (it used to run on a 20 w 50 conventional oil)

    November 8, 2018
  62. MrStoneycool69 said:

    Who's dick did she suck to get that job?

    November 9, 2018
  63. BladesNBullets 1980 said:

    Fact 0w20 oil burns

    November 13, 2018
  64. Mikkalangelo F said:

    And those of you trying to be as frugal as possible with your motorcycles, stop using automotive oil with friction reducing additives in your motorcycle that has a wet clutch and uses the same oil throughout.

    November 24, 2018
  65. tahashahbaz said:

    How many killometers i can change my engine oil 5w 30 fully syentecth plz answer me soon

    December 12, 2018
  66. DallasPilotCar said:

    should have asked what the difference is between Advanced Full Synthetic, Full Synthetic and 100 percent full synthetic

    December 12, 2018
  67. Joseph Johnson said:

    Wax based oil is junk

    December 15, 2018
  68. Sebastian Kucinski said:

    There's no damn way I'd use synthetic oil to break-in an engine. Use conventional oil just to be safe.

    December 25, 2018
  69. Bradford Ramm said:

    Why is the recommendation 5w20 synthetic blend in the USA but 0w30 synthetic in Europe on an exact same spec 2.0 focus? My guess is America’s outrageous fuel mileage requirements. Due to the oil difference I noticed a difference in change intervals also 1 yr or 10k in US And 1yr or 12.5 in Europe. FYI I did double check to make sure it wasn’t a km.

    December 25, 2018
  70. Dennis Morris said:

    I prefer conventional

    December 31, 2018
  71. jeric cordero said:

    Hello everyone, I accidentally overfilled my car with engine oil when i was doing oil change thru DIY,a half quarts less than, is it okay?

    January 8, 2019
  72. Shawn Warnick said:

    So what would make my car seem to run smoother on conventional and run worse on synthetic. I have a 2011 subaru legacy 3.6r with 83k on it so it's practically just broken in. I switched to dino oil just to see how it would run and it was shockingly better. Btw I know I'll have to change it earlier than synthetic. I figure if it seems to run better shouldn't I use that from now on as long as i follow the severe maintenance schedule.

    January 9, 2019
  73. David Price said:

    Why does 5-30 fully symthetic engine oil turn red after around 2500 miles in a 1.6 litre vauxhall astra petrol engine. Vauxhall recomend fully symthetic oil In this car.

    January 12, 2019
  74. Álvaro Sánchez said:

    Hi. My motorcycle uses semi 10w40 oil. I have in a quart a mix of liqui moly, Motul and Wolf Belgium semi synthetic on excedent from previous bottles when changing oil. Can I use this tree brand mix with identical API and JASO specs? Thanks in advance.

    January 13, 2019
  75. Kevin Martin said:

    Hey! A big issue I see with the Hondas and Acuras I service,,, I have found short trips not allowing the oil and block to reach operating temperatures allow moisture to contimate the oil leaving behind a YELLOW FILM. I would much like more information on this

    February 4, 2019
  76. James Weimar said:

    A great video!! Thank you

    February 5, 2019
  77. Sethuna said:

    Hmm, so my bikes owners manual said I should put 10w40 engine oil, but I put 15w50 (fully synthetic) in. I didn't have the manual at the time. Is it a huge problem? Seems to run fine.

    February 14, 2019
  78. Google User said:

    Actually, the term "synthetic" has no legal definition when it comes to motor oil so it is all marketing hype.
    Dino oil is being called "synthetic"
    And there is no legal definition of what percentage of mineral oil is allowed in "synthetic" oil.
    And ALL oil comes from out of the ground in some form.
    Even the holy grail of synthetics is in fact not created by man
    since it is in fact made from natural gas which came from decomposing dinosaurs and plants.
    So in the end, this is merely a way to sell the same old oil for 4
    times the price to the gullible millennials

    February 15, 2019
  79. T Samuel said:

    Disappointing. No questions about the best way to stop thin oil smoking above 100k & 200k. No clear ID for real synthetic.

    March 4, 2019
  80. David Handshoe said:

    She is totally right.

    March 6, 2019
  81. David Martin said:

    It’s better to go thicker than thinner

    March 29, 2019
  82. The Bengalee Sceptic said:

    Is this an elaborate commercial? 😂

    April 7, 2019
  83. Mantraplex said:

    thanks for presenting a professional with correct answers instead of what you think.

    April 13, 2019
  84. jeuri f. said:

    Can you mix 5W-30 with 10W-30?

    April 17, 2019
  85. xHouston Kingx said:

    Awesome vid. Thanks for the info

    April 19, 2019
  86. Jay Minasi said:

    pennzoil uses the additives levels that the Stinking Filthly EPA mandates. don't listen to this silly woman

    April 25, 2019
  87. Demetrius E. Washington said:

    This is his laziest video. lol

    May 5, 2019
  88. raider one said:

    What about mixing brands?

    May 10, 2019
  89. Miguel Salami said:

    I bet if you tied his hands behind his back he couldn't talk 🤓

    May 30, 2019
  90. Jon Smith said:

    Why is she not making a sandwich? I’m not taking advice from a woman! It’s proven they have a smaller brain.

    June 7, 2019
  91. Johnny Figueroa said:

    Engineer my ass… more like receptionist at the front desk of pennzoil Corp office

    July 14, 2019
  92. OM617YOTA said:

    Were the clips of Shanna taken from a 1995 VHS tape?

    July 14, 2019
  93. Polo Sucks said:

    I now one thing they don’t have proof so I can’t trust wat they sey

    July 17, 2019
  94. Adam King said:

    On my Turbo car, I used Liqui Moly for many years, then changed to Ravenol recently. Both are same SAE 5W40. Why does the Ravenol make my engine noticeable more responsive and lighter when both are same grade ?

    July 29, 2019
  95. aceman8448 said:

    Big question is why do mechanics recommend higher viscosity oils in high mileage engine compare to.manufactor that states to stay with same viscosity

    August 10, 2019
  96. thaik56 said:

    I wanted to hear answers regarding using different viscosity rating from the manufacturer depending on the type of climate one lives in, for instance extremely cold and extremely hot weather. Should one choose a lower before the W number viscosity for extremely cold winters and increase viscosity (2nd number) for really hot summers?

    August 11, 2019
  97. Prince Jain said:

    What does SAE, API SN, ACEA mean?
    Kindly make a video on that.

    August 17, 2019
  98. Steven Quayle said:

    You didnt ask if you could switch after using one of the other for the half life of the vehicle

    August 25, 2019
  99. MD YASEENKHAN said:

    Nice video

    September 2, 2019
  100. boostedsil40 said:

    This brings up another question,She says the manufactuer has a recommended oil but what if you live in the hot desert or freezing cold?So wouldn't running a thicker oil in summer in phoenix be better or thinner oil in anartica?I live in phoenix and this question applys because my engine recommends 5w30 so should I just leave it there during summer or go a bit thicker?

    September 3, 2019

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