Beauch11

I'm having trouble understanding how this works.

I currently use 5w-20 in my truck. 5W (Winter) - 20 (summer), if you switched oil to a 10W-30 as an example, this is said to be a thicker oil. So going from a 20(summer) to a 30 (summer) means the oil is thicker at 30? Same as the 5W (Winter) gets thicker to a 10W (Winter) you're increasing the number.. ok, so then how is it possible to have your winter oil a 5W which suggests the oil is significantly thinner than your 20 (summer) but the oil should actually be getting thicker in the winter because the outside temperature is so low that the oils viscosity should increase? How is the winter number in oil ratings lower than your summer rating???

It should be greater than your summer oil viscosity..? What am I not understanding..?

joe mcmillan

This may answer your questions:
http://www.upmpg.com/tech_articles/motoroil_viscosity/

Beauch11

Thank you but I dont believe this totally answers my question..

Does motor oil get thicker as it heats up? A cold start, your oil is to have a viscosity of 5W, but at operating temperatures it increases to a 20 weight.. So does the motor oil get thicker as the truck warms up?

WXman

http://www.bobistheoilguy.com/motor-oil-101/

Read through the Motor Oil University articles and you'll understand. Motor oil thickens as it cools. A 0W will thicken less than a 5W or 10W...which is why I will not put a 10W in my truck. You want the most "thin" oil you can get for startup, which is where most engine wear occurs. But, you still have to protect the engine once it's hot. That's where 0W40 and 0W30 oils come into play and why they are so popular now days.

Beauch11

ok, so I know now that this is not true.. Oil does not thicken as the Engine warms up.

http://www.bobistheoilguy.com/motor-oil-104/

This is a good read, I think there are a lot of people on this forum that think they know a lot about motor oil characteristics and should probably read this!!

Beauch11

Yes, thank you, this is correct. After reading the article I posted I have a better understanding now. However, if there is no oil that properly lubricates at start up to eliminate friction and excessive wear, why would car manufacturers recomend a 5w-20 for start up and not a 0W-20? From what I just learned, a 0W-20 oil should reduce start up friction further and still properly lubricate under normal operating conditions!

gregsf150stx

USE THE RECOMMENDED OIL THAT YOUR USER'S MANUAL STATES. enough said.

WestsydeGuy

In really simple terms. The oil when cold is thicker and as it heats up gets thinner.
A 5w20 oil for example will be roughly like just a straight 5 weight oil in pour ability when cold ....and about like a straight 20 weight when up to full operating temperature.
So it has the benefit of circulating quicker throughout the engine to help get the lubrication to parts when cold starting it.
Yet does not thin out as badly as a straight 5 weight oil would when hot so it helps protect the metal to metal wear if it was too thin.
Its not an exact science.
Not all 5w20 oils will flow exactly the same at a given temperature. ....think of it as more of a guideline.
Neither too thin nor too thick is ideal....so its rather a compromise.

_MacLeod_

Pretty much. Hard to go wrong with following the recommendations of the engineers with masters degrees that designed, tested and built the truck. I may play around with different brands but as far as viscocity and all that, I stick to 5W20 which is what it calls for in the manual. I know its hard to believe sometimes but those guys do know more about trucks than we do.

gregsf150stx

Chevy Silverado EcoTec3 V8 uses 0W-20. Now that's thin oil. but it states its to protect on startup.