Your 23 years old still wet behind the ears and think you know it all.
I offered my recomendations to the orignal poster and you wanted to start a war over it.
Get an engineering degree and a few years field experiance.
The light oils do not have the film stenghts for high temp high load applications.
When you can get 336,000 miles out of a 318 and have it still running strong (50psi idle 65psi driving hot) with out ever having touched a wrench to it other than oil changes, plugs and belts (stedy diet of Mobil 20w 50) or build an Offenhauser and have it stay together for the whole season come talk to me untill then you can run your water for oil and have you engine trashed before 100,000.
p.s. I still have a 40 year old 427 side oiler that I have had since new and it still kicks the *** of young guys like you.

 

Alrighty then...

 

Captain, can you explain the oil number system to me and the viscosity , which I assume is the thickness of the oil , level of each number. I know that 20w50 is a thicker oil than the 10w40 cause I used it on rotory Mazda engine, and this engine function beter with the thicker oil. But just was wondering how to tell one from the other without opening the bottle to to check with is thicker.

 

I don't know it all, but I obviously know more than you do about the protection and fuel efficiency of oil weights in various applications. You seem to think some weights that aren't appropriate for certain applications work better...that is NOT true. And I am not 23, grandpa.




What war, I was making corrections to your erroneous "experience". No war here except the one that you seem intent on creating. Stop being so sensitive, and learn to take constructive criticism.



Ah, the old college degree speech. Look pops, I have two college degrees, and I really don't think your doing a good recruiting job for engineering degrees with the "knowledge" you keep spewing. Old relics who refuse to accept the data in front of them will die a quick death in today's market. Good luck to ya.



BS! They have been tested tried and true by all manufacturers worth their salt. These have been done under extreme workload and heat conditions for miles on end. The data, research, and proof is documented. I would figure someone with your astute “experience� would know that. Face it; you are pushing old ideas that no longer have to, or need to apply.



Why do I need to come talk to you then? What you seek has already been done. 5W-20 and 5W-30 weight oils have been PROVEN to do excellent in both controlled environments and in real world experience as well as 0W-20 and 0W-40 oils. Namely taxis and police cars, but the results are just as excellent in trucks and SUV's. Engines that are not made for the specs of 5W-30 and 5W-20 don't need it, and your oil weights work in the applications that use them, but to tell a guy that his 4.7 or Hemi needs them is just false. He can have excellent engine life, and get great fuel economy running what the manufacturer suggests. Oh, and that “water� you are referring to, will and has made it well past 100,000 miles in engine applications. Stop espousing false information on here. Stop being so stubborn and stop comparing apples to oranges...it all depends on the application.




Good for you. Who are you trying so hard to convince...me or yourself?

 

Don't mean to bud in , or add to the fire , but lets get back to the topic!!!!. Can anyone answer my question with referance to the number system and how they differ in thickness one to the other. And like mulaka said : " It all depends on the aplication" . Most of use who have worked on cars as a hobby don't know it all, and this is one that I don't know. So 'smart guys' can you can you fill me in on the 411?

 

There are thick and thin oil weights in every category. The thickness or thinness of oil is also going to be determined by whether or not it is a group II, III IV, or V oil. These range from dyno to synthetic. Any oil that is a group IV is going to be a thin oil regardless of its weight. So any oil that meets the ILSAC,GF-4 spec will be a thin oil. This is due to the energy conserving requirements. If you want a thick x-30 wt, then you need to pursue oil that is API/SL oil. The viscosity grade (for example, 5W-30) you were asking about tells you the oil's thickness, or viscosity. A thin oil has a lower number and flows more easily, while thick oils have a higher number and are more resistant to flow

 

in the simplest of terms
The number refer to the viscosity the higher the number the thicker the viscosity.
multi grade oils are graded by thier equivilentviscosity tosingle grade oils.
The first number is the equivilent viscosity cold and the second number is the equivilent viscosit hot.
In the case of 10w40 it would have the same viscosity cold as a strait 10w oil and the same viscosity hot as a strait 40w oil.
In other words It's viscosity is more stable and changes less with temperature than a singel grade oil.
The higher the number the thicker the the oil ad the higher film strenght and the more resitant to being squisted out from between the bearing and the crank under high load and temperature.

example if a oil was labeled 5w50 (none that I know of but this is just an example) its viscosity would be more stable thru the temperature range than one that was labeled 10w30.
I hope this answers your question without a lot of hype.