What do the numbers on the bottles of motor oil mean?

Like 10w40





Oh, and what does the 'w' mean to.





Simple Answers pleaseWhat do the numbers on the bottles of motor oil mean?
the first number dictates the viscosity when the oil is cold so the lower the number the thinner the oil is when its cold.... second digits represent when its at operating temperature...most vehicles now use multigrade oil so its thin when its cold to provide proper protection at both temperatures in the olden times they only had one grade and so the oil would be really think when it was cold starving the motor of proper lubrication... the ';w'; should mean weight and not winter as commonly thought i was not able to find it onlineWhat do the numbers on the bottles of motor oil mean?
w is weight. Oil is rated in Viscosity which is the thickness of the oil. Your cars oil cap should say what weight to use. I recommend following that. On high mileage vehicles some people will use straight weights like 30 w(eight) which is thicker than 10 weight. BUT it can cause problems in cold winter areas. Slow cranking and so on.


Reason for multiweight is simple, example, 10 w 40, when the oil is cold the oil is thicker which means it sticks to the metal parts better when cranking the motor to start. Then as it warms up, it will thin out as thin as 10 weight. To get the best performance out of a motor you want a product that gives the ';least'; amount of friction. Thats why it is recommended to use multi grade oils and NOT straight weights.


2 identical cars, miles and everything next to each other. One has 30 straight weight, the other has multi grade 10w40. both go 400 miles, guess which car got the best gas mileage because the motor had the least amount of drag?


Does this help you understand the weights and differences?





10 weight real thin, 20 weight a little thicker, 30 weight even thicker, 40 weight even thicker, 50 weight use in racing motors 90 weight used in rear ends, worse than molasses.


Google is 10 weight thinner than 30 weight and you will see.


The colder an oil the thicker it gets.
Same idea as cooking with Crisco,





It starts off thick (your larger number) and then when the heat gets to it , it melts and thins out (your lower number)





Even though the oil thins it is still under high pressure from the oil pump, thus floating the metal parts in the engine from contact of each other. Only by thousands of an inch though.





5 w 30 is a most common winter /all season weight , check your cars book (chilton or haynes manuel ) though .








W = viscosity WEIGHT
Hey there!


The num. mean THE GRADE OF THE OIL. It verries dough on the millage on your car. So it will help to now what kind of car you have and the year of it
The w means weight, other numbers , like '32 oz' means that it's one quart.