how come so many people change to a thicker oil or think there oil is too thin?

Messages
388
I can't believe this post got like 6 likes.

Can someone explain to me how a crankshaft and a bearing or a piston and a cylinder wall, which are machined with a specified clearance between them, has a larger clearance by using thicker oil? It doesn't. It simply cannot.

That film of oil can be stronger in the space provided, but the space itself cannot physically be larger.

And I believe you meant tribology.
agreed, thats my thinking all this time
 
Messages
1,281
Location
Vancouver
I said: Higher viscosity = a larger MOFT = larger gap between moving parts = less wear and more headroom from metal-to-metal contact occurring. Trilogy 101.

You read it wrong. "Larger gap between moving parts" means a larger MOFT between moving parts. If you have more MOFT you have a larger "gap" between moving parts within their fixed clearance. Seems many here got what I was saying.

You didn't say "gap," you said gap.

As I said, you can increase the strength of the film but you are not increasing the clearance. If people want to give high fives for using wrong terminology, that's cool I guess.
 

mazda3lover

Thread starter
Messages
53
ok i guess this topic is getting very technical for a noobie like me. I guess I got my answer and it makes total sense in the regards that someone said how a specific vehicle is prescriped 5w30 in europe but 5w20 in USA, therefore obvs the manufacturer believes 5w30 provides more protection for that application.


however how do we make the conclusion for vehicles like mine or some gm trucks, i tried looking around and seems like my mazda 2.3l is always a 5w20 oil, and most gm vehicles i had in the past was always a 5w30. does that mean that the clearances for vehicles like my mazda etc are tighter therefore its best to stay with a 5w20?

lastly, if the difference was that big, wouldn't it show up in a UOA? or no?
 
Messages
728
Location
EU
ZeeOSix, you really never read anything. The responsibilities were right there: "newtonian, of high intrinsic VI and density, maybe primarily OSP, ester..." Some of it means favourable viscosity curves (viscosity in place), therefore even some operational viscosity if you like, but not HTHS-V or KV 100 or even viscosity grade. Some means other qualities.
Mazda3lover came in with lots of grades in mind and got to learn bot bingo nonsense of absolutely no value regarding his enquiry.
 
Messages
1,281
Location
Vancouver
ok i guess this topic is getting very technical for a noobie like me. I guess I got my answer and it makes total sense in the regards that someone said how a specific vehicle is prescriped 5w30 in europe but 5w20 in USA, therefore obvs the manufacturer believes 5w30 provides more protection for that application.


however how do we make the conclusion for vehicles like mine or some gm trucks, i tried looking around and seems like my mazda 2.3l is always a 5w20 oil, and most gm vehicles i had in the past was always a 5w30. does that mean that the clearances for vehicles like my mazda etc are tighter therefore its best to stay with a 5w20?

lastly, if the difference was that big, wouldn't it show up in a UOA? or no?

Thicker oil generally provides better protection. The question is whether or not you need it. Most people simply do not. It would be like if you wore football pads to go grocery shopping. I mean yeah sure I guess you are safer...?
 

mazda3lover

Thread starter
Messages
53
Thicker oil generally provides better protection. The question is whether or not you need it. Most people simply do not. It would be like if you wore football pads to go grocery shopping. I mean yeah sure I guess you are safer...?

ahh gotcha thanks that makes sense, however could we also make a case that for example maybe the thicker oil is too thick to go into places that the thinner oil could go into before? like maybe some really tight clearences? if so, then would we really know which oil is 'better'?

because for example maybe the 20 weight can reach places quicker especailly on start ups compared to a 30 weight so maybe the difference is actually negligible?
 
Messages
27,434
Location
PNW
You didn't say "gap," you said gap.

As I said, you can increase the strength of the film but you are not increasing the clearance. If people want to give high fives for using wrong terminology, that's cool I guess.
A gap is a gap ... and I clearifed the "gap" was due to the MOFT. You didn't understand a simple phenomena of how an oil film thickness is generated between moving parts ... not my fault.

With all the talk about this for years, it seems some people would kind of grasp the simple logic by now. :LOL:

And BTW, there's a difference between film strength and film thickness (MOFT) ... since you're into terminology. ;)
 
Messages
1,281
Location
Vancouver
A gap is a gap ... and I clearifed the "gap" was due to the MOFT. You didn't understand a simple phenomena of how an oil film thickness is generated between moving parts ... not my fault.

With all the talk about this for years, it seems some people would kind of grasp the simple logic. :LOL:

I know exactly how it works, which I why I called you out on your totally false statement in the first place.

Normally when people mean one thing, they say that. They don't usually say something else entirely and then backtrack later.
 
Messages
1,281
Location
Vancouver
ahh gotcha thanks that makes sense, however could we also make a case that for example maybe the thicker oil is too thick to go into places that the thinner oil could go into before? like maybe some really tight clearences? if so, then would we really know which oil is 'better'?

because for example maybe the 20 weight can reach places quicker especailly on start ups compared to a 30 weight so maybe the difference is actually negligible?

Not really. As long as the oil is pumpable (meaning you are not using it below its winter rating) the oil flow is basically the same. So both a 0w and a 10w started up at 0°C will reach the engine components downstream at the same time.
 
Messages
27,434
Location
PNW
I know exactly how it works, which I why I called you out on your totally false statement in the first place.

Normally when people mean one thing, they say that. They don't usually say something else entirely and then backtrack later.
LoL ... it wasn't a "totally false" statement ... it's a completely valid statement. Not my fault you can't understand a simple statement that's true, even though you claim you "know exactly how it works". So ironic, lol.
 
Last edited:
Messages
324
Location
Rainville, USA
I’ll move up a grade if one of my rigs burns, like my old Accord that called for 5w20, burned a qt every 2k, moved to 5w30 HM and the burn basically ceased entirely with no other ill effects. I figure the extremely negligible dent to MPGs were worth it to keep oil in the sump and out of the cats
 
Messages
728
Location
EU
In principle you can make a case. Like the individual jets of water from a showerhead need not reach the same height forever because there's algae or wax content or yoghurt culture or ice also travelling: not all points of lubrication are equally lucky. Not one temp throughout the engine, not one viscosity throughout the engine, not one shear rate throughout the engine, not one MOFT throughout the engine, not one pressure throughout the engine, not one cleanliness throughout the engine – basically often the same problem people don't want to accept.
Flow and pressure at the outlet of the positive displacement pump don't tell what's happening in each capillary at each point of lubrication.

But it's mostly not worth thinking much about. After all an oil even at 40°C could be doing funny things which a KV40 isn't expected to explain. For many winters around the globe and often all around the year 0W-20 is the answer they say. Even for cleanliness, some say (probably avoiding the technical term of the rheological hygiene :)
 
Last edited:
Messages
27,434
Location
PNW
I think there must be a lot of posting while liquor is flowing today ... 😂

You can look at any given area of an engine's clearance between parts (ie, a journal bearing, cam follower on cam lobe, rings and piston skirt to cylinder wall, etc) and see what happens when one variable is changed while holding all other variables constant. If all variables except oil viscosity is held constant, there will be a resulting thicker oil film with a more viscous oil at that given instant in time.
 
Messages
728
Location
EU
It's getting difficult to even see if you're not reading, not comprehending or not talking to me. ->#32ff
 
Messages
5,513
Location
Florida
I think America is a test dummy in this thin oil craze. What’s next 0w5 oil? -5w0? Lol.

my 2014 Mazda 3 specs 0w20. I’ve ran a 40 grade in it and the engine didn’t care. It was much quieter to my ears though but otherwise ran the same. UOA showed the same results. 🤷🏻‍♂️

these days I just stick with a 30 grade because I run it HARD and want the extra protection of a thicker oil between my bearings.
Plus this same engine elsewhere in the world specs a 30 grade.

I don’t think we will agree on this topic. It’s a never ending debate.
 
Messages
17,169
Location
...
I think there must be a lot of posting while liquor is flowing today ... 😂

You can look at any given area of an engine's clearance between parts (ie, a journal bearing, cam follower on cam lobe, rings and piston skirt to cylinder wall, etc) and see what happens when one variable is changed while holding all other variables constant. If all variables except oil viscosity is held constant, there will be a resulting thicker oil film with a more viscous oil at that given instant in time.

It’s not just today. That poster is cryptic.
 
Messages
2,856
Location
pa
lots of factors contribute to the oil film as well as its viscosity in a fully warmed running engine as the oil type as well as "advertised" viscosity varies with temperature. i enjoyed + learned from the post about pro stock bearings, noting because the large amount + type of oil used only reached 150* in the 1/4 mile run + the erica enders engine used from 3W to 7W oil depending on conditions + their oil was about 12-13 centistokes at running temp, essentially a heavy 30W! of course this is real synthetic Ester + PAO that reacts differently to heat. there is SOOO much to know about lubrication + generally only the pros REALLY know!! i use 10-30 fake synthetics in Pa weather in my pickup + Redlines real synthetics in my loose turbod 1.8L audi TT mixing 10-40 + 15-40 in winter change + topping with 15-50 in summer + have seen better vacuum readings + less consumption! girlfriends 18 kia optima 2.4L gets fake synthetic 10-30 + uses NONE!!!
 
Messages
981
Location
Upper midwest
Although there are a few exceptions out there, I view oil weight experimentation much like tweaking tire pressures or alignment angles. Within reason, personal preference is just that. Personal preference. If a OE said you could only use brand X fuel, and one day you decided to try brand Y knowing full well it was an acceptable substitute, would it be along the same line of thinking? No, it would be considered silly.

OE's have to provide a set of specifications to guarantee that what they're selling will do it's job safely, reliably, and perform within design parameters AT LEAST through the warranty period, although we all know modern vehicles are designed to go far beyond that.

For example: among the multitude of family vehicles I maintain are a 2011 CR-V and a 2018 Accent (same household). The Honda spec's 0W20, the Hyundai 5W20. As many K24's tend to do, the CR-V started burning about 1.5 quarts every 1k miles running 0W20. I told my dad to just buy 5W20 for both, full synthetic as that's what both have been getting since new. No HM, nothing fancy. Just quality oil. Did it have any negative effects on the Honda? Absolutely not, in fact quite the contrary. The oil burning is now down to about 1.5-2 quarts per 5k oil change.

The same can be said for tire pressure. Sure, the OE spec is optimal, however I've been running my tires about 5 pounds high on my Volt and about 3 pounds high on my Jeep and both times it's worked out great. The Volt handles sharper in corners, rides exactly the same, gets better electric range, and the tires have worn absolutely perfect for the last 25k miles. The Jeep is a lot less "floaty" with a few extra pounds, and doesn't lean quite so much on high speed curves.
I disagree "OEM tire pressure specs are optimal", for the EXACT reason you stated why you changed yours with zero wear issue and only a multi upside of advantage in almost every car you try this in. Most of those spec are too low and a lot vehicles are more dangerous in an accident avoidance with reduced handling in common everyday driving.
 
Top