10w-60 My reasoning, an explanation
Discussion
I get asked all the time "why do you advise against the use of 10w-60?".
Let's get one thing clear, I supply 10w-60 and recommend it where it is appropriate for the engine or the application but conversly I caution against it's misuse!
I have debated this many times on many car forums and I know there are some that do not agree with me however I have never had a reasonable technical explanation why 10w-60 is in fact suitable, it's certainly not mentioned in the handbooks of many modern highly tuned performance cars, with the exception of some Alfa Romeos for "spirited driving" whatever that is meant supposed mean.
Explaining this is diffucult so there may be questions but I'll try my best to explain it in plain English!
Lets look at what oil specs actually mean and particularly the higher number which is in fact the oils SAE number (the "w" number is in fact the cold crank viscosity and measured in a different way) The SAE number is measured by the oils viscosity at 100degC.
Your cars require according to the manufacturers specs, sae 30, 40 and in some cases sae 50.
To attain the relevent sae number the oil has to be at 100degC (no thinner than)
SAE 30 11cst approx
SAE 40 14cst approx
SAE 50 18cst approx
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid.
As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in centistokes (cst) and usually measured at 40degC and 100degC.
SAE 60 is in fact 24cst viscosity at 100degC!
This is 33% thicker than an sae 50, 70% thicker than an sae 40 and over 100% thicker than an sae 30!
So, what's the problem with this thickness?
Well, this is measured at 100degC and at lower temps (70-90degC) all oils are thicker than at 100degC so the problem is compounded to some extent.
The downsides of such a thick oil (when not specified) are as follows:
Additional friction, heat and wear.
A reduction of BHP at the wheels
Lower fuel consumption
The thicker the oil is the more friction and drag and the more power the engine needs to move it around the engine which inevitably translates to less at the wheels.
So, when do we spec a thicker oil?
Well, you will probably have seen us on occassions recommending a 10w-50 but only in these circumstances.
1. If the car is heavily modded and heat/oil temperatures are excessive.
2. If the car is used on track and heat/oil temperatures are excessive.
3. If it's required by the handbook.
Our criteria for this is based on oil temps as an sae 40 semi-synthetic can handle around 110degC for limited periods whereas a proper synthetic sae 40 can hande 120-130degC for prolonged periods due to its thermal stability.
Once you see more than say 120degC for prolonged periods an sae 50 is adviseable as it is 18cst at 100degC and still 11cst at 130degC! This is in fact the same as an sae 30 at 100degC.
More importantly at 90degC an sae 40 is 15cst, an sae 50 is 20cst and an sae 60 is 30cst!
In a worst case scenario with thick oils (when not required) is that you will experience air entrainment and cavitation inside the bearings at high RPM. Not clever stuff!
I know this is technical stuff but oil is a combination of science and engineering and few people know enough about it to make an informed choice. Just because your mates use it and have had no problems is not a good enough reason to use it, your engine would prefer and benefit from the correct oil.
Cheers
Simon
Let's get one thing clear, I supply 10w-60 and recommend it where it is appropriate for the engine or the application but conversly I caution against it's misuse!
I have debated this many times on many car forums and I know there are some that do not agree with me however I have never had a reasonable technical explanation why 10w-60 is in fact suitable, it's certainly not mentioned in the handbooks of many modern highly tuned performance cars, with the exception of some Alfa Romeos for "spirited driving" whatever that is meant supposed mean.
Explaining this is diffucult so there may be questions but I'll try my best to explain it in plain English!
Lets look at what oil specs actually mean and particularly the higher number which is in fact the oils SAE number (the "w" number is in fact the cold crank viscosity and measured in a different way) The SAE number is measured by the oils viscosity at 100degC.
Your cars require according to the manufacturers specs, sae 30, 40 and in some cases sae 50.
To attain the relevent sae number the oil has to be at 100degC (no thinner than)
SAE 30 11cst approx
SAE 40 14cst approx
SAE 50 18cst approx
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid.
As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in centistokes (cst) and usually measured at 40degC and 100degC.
SAE 60 is in fact 24cst viscosity at 100degC!
This is 33% thicker than an sae 50, 70% thicker than an sae 40 and over 100% thicker than an sae 30!
So, what's the problem with this thickness?
Well, this is measured at 100degC and at lower temps (70-90degC) all oils are thicker than at 100degC so the problem is compounded to some extent.
The downsides of such a thick oil (when not specified) are as follows:
Additional friction, heat and wear.
A reduction of BHP at the wheels
Lower fuel consumption
The thicker the oil is the more friction and drag and the more power the engine needs to move it around the engine which inevitably translates to less at the wheels.
So, when do we spec a thicker oil?
Well, you will probably have seen us on occassions recommending a 10w-50 but only in these circumstances.
1. If the car is heavily modded and heat/oil temperatures are excessive.
2. If the car is used on track and heat/oil temperatures are excessive.
3. If it's required by the handbook.
Our criteria for this is based on oil temps as an sae 40 semi-synthetic can handle around 110degC for limited periods whereas a proper synthetic sae 40 can hande 120-130degC for prolonged periods due to its thermal stability.
Once you see more than say 120degC for prolonged periods an sae 50 is adviseable as it is 18cst at 100degC and still 11cst at 130degC! This is in fact the same as an sae 30 at 100degC.
More importantly at 90degC an sae 40 is 15cst, an sae 50 is 20cst and an sae 60 is 30cst!
In a worst case scenario with thick oils (when not required) is that you will experience air entrainment and cavitation inside the bearings at high RPM. Not clever stuff!
I know this is technical stuff but oil is a combination of science and engineering and few people know enough about it to make an informed choice. Just because your mates use it and have had no problems is not a good enough reason to use it, your engine would prefer and benefit from the correct oil.
Cheers
Simon
Opieoilman, doesn't the engines bearing clearance have something to do with it as well.
In other words if an engines has tight bearing clearances it's best to use an oil with a lower viscosity, the thinner oil will get between bearings and races and protect like it's supposed to, but if the engine has tight clearances and you use an oil with too much viscosity it can't easily get in and causes all of the problems you mentioned especially premature wear.
I am assuming that you meant to say higher fuel consumption?
In other words if an engines has tight bearing clearances it's best to use an oil with a lower viscosity, the thinner oil will get between bearings and races and protect like it's supposed to, but if the engine has tight clearances and you use an oil with too much viscosity it can't easily get in and causes all of the problems you mentioned especially premature wear.
opieoilman said:
The downsides of such a thick oil (when not specified) are as follows:
Additional friction, heat and wear.
A reduction of BHP at the wheels
Lower fuel consumption
I am assuming that you meant to say higher fuel consumption?
Presumably in a tight bearing clearance the shear effect on the oil increases it's temperature considerably so it's viscosity in the bearing itself reduces therefore it leaks out fast .. but because the oil being pumped to the bearing is cooler it is thicker, therefore you might get a situation where the oil actually *between* the bearing surfaces is *less* with a thicker viscosity oil than a thinner viscosity oil.
As it's the hydrodynamic wedge that builds up because of a full fluid film then if the oil leaks out of the bearing clearance faster then the bearing wont be separated as fully by the hydrodynamic wedge.
I had some good news today .my local motor factors are starting to stock motul 300v oil ..
As it's the hydrodynamic wedge that builds up because of a full fluid film then if the oil leaks out of the bearing clearance faster then the bearing wont be separated as fully by the hydrodynamic wedge.
I had some good news today .my local motor factors are starting to stock motul 300v oil ..
personaly i think the 50 weight oil is the way to go for any rv8 engine, i ran an engine on the dyno an popped the valley open to see what was going on in there and the oil leakage out the followers when hot is incredible espeicially on solid lifters, a 40 weight and you just end up with low oil pressure!
So am i doing the wrong thing by useing castrol rs 10/60 in my fiesta rs turbo ????? All the spechilists i have spoken to have recommended it . The normal running temp for oil is around 115c i have seen it as high as 135/140 (Temp probe is at return side of the oil filter) when being driven hard would i benifit from haveing an oilcooler and running 10/40-50 ???
Its just i have been led to beleive that the optimum running temperature is 90 deg from expert engine builders like david vizard etc.... are these wrong then? i must admit i only work with the rover v8 engine and at 90 with a non ester based fully synthetic it seems about right anything over 120 deg and you get huge drops in oil pressure and start running big ends
A decent fully synthetic will work in the range of 80-120degC.
The drop in pressure will be the viscosity of the oil at 120degC.
The answer is to use a good sae 50 race oil which is more resistant to thinning or install an oil cooler and switch to a thinner viscosity oil.
Cheers
Simon
The drop in pressure will be the viscosity of the oil at 120degC.
The answer is to use a good sae 50 race oil which is more resistant to thinning or install an oil cooler and switch to a thinner viscosity oil.
Cheers
Simon
Thanks simon its just that i have contributed to a thread in the chrimera section tvr about oil coolers, all i was saying was that 90 deg for me is a temperature where i would be thinking of fitting a cooler if it creeps much higher than this? surely even the oils like the silkoline pro although they can handle high temperatures surely you are better off running a thinner oil and trying to run the temperature around the 90-100 mark after all not only is the oil a lubricant it is also a cooler to the engine components?
Simon,
Penrite appear to take opposite view, probably due to lack of esters.
www.penrite.com.au/nextpage.php?navlink=db/bulletinview.php&id=20
The old thinking (mineral oil based IMO) is higher viscosity and high ZDDP although fuel dilution may be more of an issue with carbs.
Penrite appear to take opposite view, probably due to lack of esters.
www.penrite.com.au/nextpage.php?navlink=db/bulletinview.php&id=20
The old thinking (mineral oil based IMO) is higher viscosity and high ZDDP although fuel dilution may be more of an issue with carbs.
Hello Simon,
the 10W-60 caught my eye as I have an Alpina Bi-Turbo and in the engine bay is a Castrol RS 10/60 sticker with Alpina endorsement. The engine is a 3.5 litre 6 cyl twin turbo which has now covered 120,000 miles. Oil temp during normal running is between 80 and 100 degrees - pressure is limited to 5.0 Bar, with 1.8 Bar at idle being the norm. As far as I know, it's always had 10/60
I've read recently that Castrol RS 10/60 is not the same as the RS 10/60 that was around 12 years ago when the car was new. I wrote to Castrol recently and they thought I should continue with the same oil, although they didn't recognise the engine.
From reading your post, I've been wondering whether I should change the oil to suit modern availability - can you offer any advice here?
Thanks - Dave.
the 10W-60 caught my eye as I have an Alpina Bi-Turbo and in the engine bay is a Castrol RS 10/60 sticker with Alpina endorsement. The engine is a 3.5 litre 6 cyl twin turbo which has now covered 120,000 miles. Oil temp during normal running is between 80 and 100 degrees - pressure is limited to 5.0 Bar, with 1.8 Bar at idle being the norm. As far as I know, it's always had 10/60
I've read recently that Castrol RS 10/60 is not the same as the RS 10/60 that was around 12 years ago when the car was new. I wrote to Castrol recently and they thought I should continue with the same oil, although they didn't recognise the engine.
From reading your post, I've been wondering whether I should change the oil to suit modern availability - can you offer any advice here?
Thanks - Dave.
We contacted Alpina a year ago about this and the answer was unusual but here it is anyway!
thank you very much for your e-mail.
ALPINA is working together with CASTROL for a long, long time and we recommend oils from CASTROL for our engines. But it is also possible to use every oil which is recommended by BMW for that engine type.
The BMW ALPINA B3 3,3 for example is filled with CASTROL SLX 0W-30 and has a sticker that ALPINA recommends that oil. We also recommend CASTROL TWS 10W-60 for those engines especially for cars which use a little more oil.
Both oil qualities were tested by us and there should be no worry about using TWS.
Best regards
Axel Rimpler
Leiter Kundendienst / Manager, customer service
Ok, forget the plug for Castrol a minute because they're paid to do that but you can use both 0w-30 or 10w-60?
Have you ever held a bottle of each and shook them or looked at them in a tube? - they couldn't be further apart viscosity wise!
So, what to do? We'll start to look at certain factors and then decide what the best oil is to use, so:
What type of driving do you do?
What oil temps do you see in normal driving and pushing hard?
The problem is we need to be more scientific than use 0w-30 or 10w-60.
Let me know and I'll get back to you.
Cheers
Simon
thank you very much for your e-mail.
ALPINA is working together with CASTROL for a long, long time and we recommend oils from CASTROL for our engines. But it is also possible to use every oil which is recommended by BMW for that engine type.
The BMW ALPINA B3 3,3 for example is filled with CASTROL SLX 0W-30 and has a sticker that ALPINA recommends that oil. We also recommend CASTROL TWS 10W-60 for those engines especially for cars which use a little more oil.
Both oil qualities were tested by us and there should be no worry about using TWS.
Best regards
Axel Rimpler
Leiter Kundendienst / Manager, customer service
Ok, forget the plug for Castrol a minute because they're paid to do that but you can use both 0w-30 or 10w-60?
Have you ever held a bottle of each and shook them or looked at them in a tube? - they couldn't be further apart viscosity wise!
So, what to do? We'll start to look at certain factors and then decide what the best oil is to use, so:
What type of driving do you do?
What oil temps do you see in normal driving and pushing hard?
The problem is we need to be more scientific than use 0w-30 or 10w-60.
Let me know and I'll get back to you.
Cheers
Simon
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