Thick oil...Or thin...???

geeeman · Oct 20, 2003

Mercedes SLR - 5w50
Ferrari 360 - 10w60
Bmw M... - 10w60
Mustang Cobra 15w50 ( I think...?)

See a pattern here?...ultra high performance, usually high revving...Why do these engines spec such thick oil?

Yet...Honda, Ford etc are moving towards 20w...Why? Fuel economy only, or start up protection taking precedence over op. temp. protection... or simply adequate in the application?

Are thin oils over-rated for protection?; are thick oils better in extreme applications???

Opinions Anybody...

PS - My high mileage (360 000 km) engine likes slightly thicker oil...much quieter on 0w40 M1, seemed a touch slower on 15w50 though.
(psychological? ... probably!!!)

sprintman · Oct 20, 2003

50W is only thick to those in NA. 70W is thick. Commonly available oils are 20-70W so 45W would be middlweight, 50W a tad more. Way too much time on BITOG spent worrying about viscosities by just about everybody self included. Additive package and basestock quality appear more important after looking at all the UOA's here for a long time now.

Last_Z · Oct 20, 2003

I am comfortable running a 40W during summer and 30W during winter.
Rick

darkdan · Oct 20, 2003

I'm pretty sure the Cobra gets Mobil 1 5w30 from the factory.

sprintman · Oct 20, 2003

Cobra R is M1 15W50 from factory

Patman · Oct 20, 2003

quote:

Originally posted by sprintman:
Cobra R is M1 15W50 from factory

The Cobra R is an older version (1999?) which came with a 351 in it, an engine that was originally designed quite a long time ago. The newest supercharged Cobra does not come with 15w50.
That Cobra R was basically a road race car, you couldn't even buy it unless you had an SCCA or similar licence. So the 50wt oil is needed since oil temps during road racing get very very high. Running a 50wt oil during a road race is like running a 30wt oil during daily driving, since during the race the oil gets hot enough to thin out to the same viscosity as 30wt. (in other words, 50wt at 270F is probably the same thickness as 30wt at 210F)

Leo · Oct 20, 2003

I reckon go the 50wt man. No harm in using it at all, especially with that kinda mileage! Over the weekend i put some cheapy API SF rated 20w-50 in my car and drove around for about 20ks just to flush out all the junk after my Auto-RX interval. And I noticed the engine was quieter and a tad smoother on idle with the thicker oil than it was on the Penz 15W-30.... Needless to say the oil went dark black!

Al · Oct 20, 2003

I think Patman hit it pretty well. Ideally lubrication should be " The right amount, of the right type (including viscosity), at the right place, and at the right time"

A thick oil will protect better at very high temperatures. But if it's too thick the vehicle will run hotter bc of the higher viscosity and it may be too thick to get to the places where it is needed if too thick for the temperature. So it's all a balancing act. High load, high temp, looser clerances need a "thicker oil".

I think that 50 wt. is seldom needed-in normal driving.

buster · Oct 20, 2003

Patman and Al summed it up. Just depends on the engine. The cars mentioned above are pushing a ton of HP so thicker weights are obviously the right call. Leave it to the engineers who build the cars to determine the right viscosity. IMO, they know best even if pressures from other parties are intervening.

Primus · Oct 20, 2003

quote:

Originally posted by geeeman:
Mercedes SLR - 5w50
Ferrari 360 - 10w60
Bmw M... - 10w60
Mustang Cobra 15w50 ( I think...?)

See a pattern here?...ultra high performance, usually high revving...Why do these engines spec such thick oil?

Yet...Honda, Ford etc are moving towards 20w...Why? Fuel economy only, or start up protection taking precedence over op. temp. protection... or simply adequate in the application?

Are thin oils over-rated for protection?; are thick oils better in extreme applications???

Design peculiarity of given engines and relative requirements for oil: higher film strength at HT/HS and better combustion chamber sealing. Over this, 50-60 viscosity oils ensure certain reserve of protection if even they are diluted by fuel. In UAO forum, topic "Subaru oil tests - Dutch source" I posted the link where you would find how the viscosity of different oils drops (with or without dilution) after 1000-13000 km of race.

Regarding high revving engines, the notion is quite relative. In fact, the engines of mentionned cars are high revving relatively to some commonplace cars. For high revving engine, say with average RPM over 7.000, 20 viscosity oil would really suit more provided the viscosity ensures not only hydrodynamic lubrication, but also enough to work at big end-bearings and camshaft lobes where the shear rate is the highest. Obviously new Honda and Ford engines are designed so that 20 viscosity is quite enough to create hydrodynamic lubrication and protect at low RPM (800-1000), but not to suffer of shear induced changes at high RPM (5000-6500) in critical areas. For the same reasons, probably, for some Ferrari models are prescribed only 10W-60 and for others - only 0W-40.

Dr. T · Oct 20, 2003

No, actually it's an X-90. In either case, my point being that in instances such as this one where the viscosity in non-cafe oriented, what we're seeing is thicker viscosity being recommended because it provides the needed protection so that the engine doesn't blow up. For the rest of us...guess it's OK to use 5-20...that is, until the next batch of sludged-up cars comes along...eg. Durango's. At least the "experts" on the board here know about auto-rx and that product will "make everything better".

Primus · Oct 21, 2003

Dr.T,
Sorry, but you took my post and Yannis comments in a wrong way. The idea is to use for any aggressive driving or during summer time preferably the oil heavier then 0W-30, 5W-30 or 0W-40, if even the latters are ACEA A3/B3 qualified synthetics and approved by number of OEMs. May be I'm wrong, but I still do not feel a confidence in any oil with weight lower then 40.

Yannis,
Looks like you have realized to open the Dutch link. Would you confirm ? Thank you in advance.

yannis · Oct 21, 2003

quote:

May be I'm wrong, but I still do not feel a confidence in any oil with weight lower then 40.

Me too !!! shhhhhhhh keep it quite "they" will hear us ...we are in bob's site ,not in europe

[/QUOTE]
Yannis,
Looks like you have realized to open the Dutch link. Would you confirm ? Thank you in advance. [/QUOTE]
Yes sir ,i have opened the dutch link and the one that impressed me was the lack of any german oil!!
Not even a dutch oil...which helped to remember that i had used a dutch 5W-50 oil a few years ago ..Beverol and just before that Aral's 5W-50

Now about my 10W40 reconsideration ...this report proves that this type of oil does its job perfectly at least for short drain intervals and since i push to the red line often , i don't feel comfortable leaving any oil more that 3-4000 miles .
So 10W40 looks pretty good to me for 3000 miles.

Dr. T · Oct 21, 2003

I don't think so...I completly agree. Having used an A3-30 weight for some time with poor results I completely confer with not using any oil less than a 40 weight for any vehicle as a minumum. Upping the ante concurent with engine performance stature from there as required.

I think 30 weight A3 oils are just the start...but, also fall short of being adequate/ideal in many cases.

Patman · Oct 21, 2003

quote:

Originally posted by Dr. T:
I don't think so...I completly agree. Having used an A3-30 weight for some time with poor results I completely confer with not using any oil less than a 40 weight for any vehicle as a minumum. Upping the ante concurent with engine performance stature from there as required.

I think 30 weight A3 oils are just the start...but, also fall short of being adequate/ideal in many cases.

How can you say that with such confidence when we see such amazing UOAs on here with 30wt oils? Just look at Stuart's UOA, easily the best one on here, are you trying to tell me he'd see lower wear with a thicker oil?

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000920

You'll get the chance to see actually, since he's now running a 40wt oil. I highly doubt he'll beat these numbers he ran with 10w30 Schaeffer Oil though!

Also, I don't mean to pick on you but you always say how you've had such great results with these thick oils, but yet not one single UOA to prove yourself. As a matter of fact all of the people on here who claim that the 40 and 50wt oils are the way to go often don't have any UOAs to back themselves up either.

Like it's been mentioned before on here many times, every engine has a specific viscosity it likes the best, and of course this can change slightly up or down depending on the climate and how the person drives it too.

So to come right out and say that every car needs at least a 40wt oil simply is not true. In fact we've seen some super low wear numbers from some cars with 5w20 and 0w20 too! Why would someone who has good UOAs with those oils want to go to something thicker and just lose MPG? And if you're seeing 0ppm of lead wear when using 0w20, there simply is no reason to switch.

The thick vs thin debate will rage on forever, but truthfully the real answer to the question is that each situation is unique and one viscosity does not fit all!

[ October 21, 2003, 03:59 PM: Message edited by: Patman ]

yannis · Oct 21, 2003

Well...Stuart used 10W30 bobzoil with lube control.Doesn't this thickens the oil nearly to 10W40?

Patman · Oct 21, 2003

quote:

Originally posted by yannis:
Well...Stuart used 10W30 bobzoil with lube control.Doesn't this thickens the oil nearly to 10W40?

Nope, his viscosity ended up at 11.03 which is a middle 30wt.

yannis · Oct 21, 2003

quote:

Originally posted by Patman:

quote:

Originally posted by yannis:
Well...Stuart used 10W30 bobzoil with lube control.Doesn't this thickens the oil nearly to 10W40?

Click to expand...

Nope, his viscosity ended up at 11.03 which is a middle 30wt.

Come on....not even a synthetic could keep its viscosity for so long unless it was starting to slugging up.
Actually Stuart's UOA may justifies Bob's opinion that additives play the biggest part in the oil formulation and not the base oil.

buster · Oct 21, 2003

quote:

Also, I don't mean to pick on you but you always say how you've had such great results with these thick oils, but yet not one single UOA to prove yourself. As a matter of fact all of the people on here who claim that the 40 and 50wt oils are the way to go often don't have any UOAs to back themselves up either.

Like it's been mentioned before on here many times, every engine has a specific viscosity it likes the best, and of course this can change slightly up or down depending on the climate and how the person drives it too.

So to come right out and say that every car needs at least a 40wt oil simply is not true. In fact we've seen some super low wear numbers from some cars with 5w20 and 0w20 too! Why would someone who has good UOAs with those oils want to go to something thicker and just lose MPG? And if you're seeing 0ppm of lead wear when using 0w20, there simply is no reason to switch.

yes, yes yes! Patman is right. Everyone should read this! Especially Dr.T and other thick oil lovers.

Shannow · Oct 21, 2003

buster, while I agree with Patman on the small number of UOAs using the thicker oils, anecdotally at least they do the job.

Given that Oz has only recently discovered the lightweight oils (that's the XW-40s), there are many millions of engines that have run 250,000km on dino 20W-50s and do not consume half a litre of oil in their 10,000km oil change intervals.

The average Oz motorist when he starts to use a dipstick's worth of oil in 10,000km starts to worry about the state of rings and valve guides.

Thick oil...Or thin...???

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