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Oil weight question for Rich Rohrich

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Posted by: OnAnySunday

Yea, here's another one.:
A customer of mine owns a local "quick lube" service center.
He's been in buisness for quite some time, and i respect his opinion.
But the other day he told me something that has me wondering....
It's about oil weights (viscosity).
I mentioned to him that i used to use 20w-50 (Mobil-1) in an old Thunderbird GT i used to own.
He told me that a heavier oil (20-50 or even 10-40) holds more heat in an engine than a lighter (5-30 , 10-30) oil.
Supposedly in his opinion, using a heavier oil in the summer will make an engine run hotter, not cooler.
And he says a lighter oil will dissipate heat much quicker.
Is there any truth in this?
If this is so, then wouldn't running 5-30 oil in my bike be better than the 10-40 i'm using now?
He also claims that thinner oil is better in new cars because of the tighter tolerances in todays modern engines.
In fact he says there is going to be a new weight of oil for newer cars (0-30 and 0-20).
Gosh that would be as thin as water i would think!!
Any input on this would be appreciated.
Thank you.


Posted by: RM_guy

I’m curious about this too. I saw 0W-30 oil advertised the other day and chalked it up to a misprint. I have heard that the new cars spec lower viscosity’s due to the tighter tolerances in the engine. Both my newer vehicles (’96 & ’98) spec 5W-30.


Posted by: marcusgunby

Mobil has made a 0W 40-its been around in the UK for a while.I think its because we have alot of small high revving 16valve motors.


Posted by: J.B.426

One factor that I believe contributes to the increased recommendations for lighter weight oils by manufacturers is that they can get better gas mileage with it. It may be a minute amount but you know the environmental story. Someone feel free to correct me if I'm wrong.


Posted by: Nevada Sixx

i think higher weight oils my well run a little hotter, but can hold up very high heat, like in the summer, better than a light oil. i used 5w30 in my camaro for 10 years, and engine ran great when i sold it.


Posted by: mopowa

It has been my understanding that heavy wt
oils generate and retain heat more than lighter oils, given they are both providing adequate lubrication, hence heavier than needed is not always good. As for the "weight rating" of oil, the numbers are unitless numbers used only to describe the the temp characteristics of the oil. 0w oil will still be substatially "thicker" than 30w 40w or 50w at a lowered temp and should not be a cause for alarm. It is a better oil in most repects unless the index improvers used cause deposits or ring sticking.


Posted by: bwalker

Mopowa, A 0 weight oil would be thinner than a 30w or 40w at low temperatures.

I believe the reasons you are seeing car mfg spec lighter oils has to do with CAFE. A mpg here and there can really help the big 3 as they sell a huge amount of trucks and SUV's that really suck down the gas.

------------------
Ben Walker
00 cr 250
BRC,AMA,NRA Member
"If Harley built a helicopter would you fly in it?" Unknown sage


Posted by: oilman

I have been using 0w/30(Amsoil) for over 4 years now. It is not as thin as water it still has to meet the criteria for a 30 weight oil. I like it because my truck starts easy in the winter time. I think it has a pour point of 74 below zero. I also have used it in the crankcase of the KDX for years now in both the summer and the winter. The original clutch has never slipped with this 30w oil.


Posted by: Rich Rohrich

Quote:
Originally posted by OnAnySunday:
He told me that a heavier oil (20-50 or even 10-40) holds more heat in an engine than a lighter (5-30 , 10-30) oil.
Supposedly in his opinion, using a heavier oil in the summer will make an engine run hotter, not cooler.
And he says a lighter oil will dissipate heat much quicker.
Is there any truth in this?


I've never really given it much thought, but I'd be inclined to think the risks of running very light oil far outweigh any potential cooling advantages (IF they exist). There's a lot more to the cooling abilty of oils than a simple viscosity comparison. Whichever you choose to believe I think you'd have a pretty tough time proving it http://dirtrider.net/ubb2/smile.gif

Quote:
Originally posted by OnAnySunday:

In fact he says there is going to be a new weight of oil for newer cars (0-30 and 0-20).
Gosh that would be as thin as water i would think!!
Any input on this would be appreciated.
Thank you.


The high quality of current oils and the potential mileage benefits are part of the reason for the use of lower viscosity oils, but the main reason is a series of recent past changes and an upcoming mandatory change in the SAE J300 low temperature tests and standards. These standards go into effect later this year, and will cause oils to be reclassified downwards in many cases. So a 10w30 oil you buy today will likely be reclassified as a 5w30 in the fall.




Posted by: wrench

So, does that mean that a 15w50 will become a 7.5w50 (based on your example) this fall as well?


wrench


Posted by: Rich Rohrich

No, more like the 15w50 you buy in the fall will probably be closer to today's 20w50


Posted by: Buckholz

I can only think of two reasons a thicker oil would result in more heat.
1) Takes more energy to shear a thicker oil. So, the very slight power increase one gets with thinner oils comes from a reduction in heat generated in the oil.

2) Less active convection in the oil sump. Probably very minimal effect, as the oil is constantly being circulated, bounced,....


I would guess that your buddy might be correct technically, but with no practical (measureable) difference in the engine oil heat/vicosity question.


Posted by: mopowa

Let me try this again.
0w oil at most ambeint temps.
(you pick your favorite riding temp) will still have a higher dynamic viscosity(lb-s/ft^2) than 30w at peak engine operating temp.
More specifically;
10w oil@50degF 3x10^-3 lb*sec/ft^2
30w oil@180degF 4x10^-4 lb*sec/ft^2

Or it may be easier to think of a fluids
viscosity to be constant(its not,thats what the index number is)than

SAE10w oil @ 100degF = SAE30w oil @ 160degF

Which happens to be...
If you really want to know than look at a
ASTM graph for common newtonian fluids.


Posted by: mainjet37

mopowa, i thought i told u to NEVER! use ur time @ pennzoil in anger again! now i get to ride ur bike all day at elizabeth city on practice day, hahaha (like thats not what would happen anyhow.)


Posted by: mopowa

Or it may be easier to think of a fluids
viscosity to be constant(its not,thats what the index number is)than

forget that. Thats only a small part of the index number which is the cause of a lot of confusion.
Next time you go to Trak Auto ask the counter
person what the dynamic viscosity of of a particular oil is during start
up,practice,first turn,and white flag lap.
If any number sounds alarming to you than
go ask that golfer that does the
Penzoil commercials. Im tired of looking at this graph.


Posted by: mainjet37

mopowa, off the subject practice at ecmx is feb 4th. u up to it im off from work.


Posted by: mopowa

Mainjet...Im trying to have an indepth discussion on viscosity index. The though
of you wadding up my bike AGAIN is ruining my concentration. Go listen to your Korn cd
and pretend your wife will let you buy a bike with her tax return.


Posted by: bwalker

Mopowa, Are you saying that a 0w oil is of heavier viscosity than a 30w at equal temps? Or are you trying to say that a 30w at engine operating temp is thinner than a 0w at room temp?


------------------
Ben Walker
00 cr 250
BRC,AMA,NRA Member
"If Harley built a helicopter would you fly in it?" Unknown sage


Posted by: mopowa

no and yes

The point I was trying to make is that the low number in a multivis oil has no effect when the engine is at operating temp. It does have an effect when the oil is at room temp and even though the index improvers help to thin the oil out at lower temps it is still not thinned more than the upper number at operating temps.
Ideally a even wider index would work better though the "magic" additives used to "improve" the index can cause problems with ring sticking and deposit when used in a combustive application.


Posted by: bwalker

Mopowa, Thanks for the clarification.I agree 100%.

------------------
Ben Walker
00 cr 250
BRC,AMA,NRA Member
"If Harley built a helicopter would you fly in it?" Unknown sage



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