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Discussion Starter · #1 ·
Interesting stuff. I use Magnatec 10sw40 which has worked wonders for years, but some people do use the 10sw60 in the E34.

Might be worth reading this and making your own mind up.


From "Oilman", Simon, over at Northloop.


"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 which stands for winter 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
Higher 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 you have used it and had no problems is not a good enough reason to use it in the wrong application, your engine (if it could say and some can) would prefer and benefit from the correct oil.

Cheers
Simon"
 
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All I know is that I use a litre of magnatec 10w40 every 4-500 miles, compared with 1800 miles for a litre of Silkolene Pro-R 15w50 (which I get a around £5 a litre.

Conclusion: I'd rather top up every 1800 miles than every 400 miles
 

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Just to add, when i was getting my tyre prices at Costco yesterday I saw they had Mobil 1 0w-40 at £24 a drum, not bad. I've been using this oil as it was recommended by a certain 'specialist' but reading previous posts it would seem that this oil is too thin, i've definately noticed higher oil consuption since I switched from Castrol ( which was either 5w or 10w )

MIKE.
 

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It also has to do with the conditions of the seals etc.

S38's are known to sweat a lot, and with thin oil it becomes more.

However, I've been running Valvoline full-synth for a while to clean my engine up, and it works perfectly. Will be replacing for Mobil when I replace the half-shaft rubber at some point this month.
 

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Discussion Starter · #6 ·
All I know is that I use a litre of magnatec 10w40 every 4-500 miles, compared with 1800 miles for a litre of Silkolene Pro-R 15w50 (which I get a around £5 a litre.

Conclusion: I'd rather top up every 1800 miles than every 400 miles
It's not the oil use that's at issue here, it's how thick that "50" oil is at normal temps compared to a 40 or 30.

If the oil is much thicker at normal temperatures for the S38 engine, then the choice in your case becomes one of whether the issues (Additional friction, heat and wear, a reduction of BHP at the wheels, higher fuel consumption) outweigh the inconvenience of you topping up more frequently.

Perhaps you should try a Silkolene 15w40 or 10w40 if such a grade is available from them.

Regards

Ivan
 

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Discussion Starter · #7 · (Edited)
It also has to do with the conditions of the seals etc. S38's are known to sweat a lot, and with thin oil it becomes more.
Completely right as usual Wout. However, running 10w60 oils as some people are wont to do is using a thicker one than factory. I know 0w40 in Mobile 1 has caused leaks that 10w40 does not, but given the dramatic increase in viscosity if Simon's post is accurate, why go thicker than factory unless oil temp is very high in a pure racing environment?

Still, at least our knowledge grows every day. It's better to have the choice and a reason behind it rather than just think "Ah. E39 M5 was changed to 10w60 so this must be better".

Regards

Ivan
 

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Off the top of my head, I 'think' I am using Pro S 5w40 (but I'd have to check as it's probably the 10w50 version).
 

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Interesting post thanks.

I switched to TWS 10-60 this summer, oil consumption is nil but I worry that it may be too thick. I mean my oil temp is usually around 100, but never over. Maybe it does more harm than good!

Lantz
 

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I'm one of the happy TWS 10W60 users, and will continue to do so. Not only in my BMW, but in a lot of other "intensively used" vehicles too. A "sportingly used" Alfa among others....

Why is it that every Alpina built and Alpina modified BMW engine sports a big sticker stating "Alpina reccomends Castrol TWS 10w60" while those engines are nothing more then the same basic parts, bearings, pistons, hydrolifters etc. as in their BMW counterparts, just working a lot harder? They wouldn't reccomend that oil for no reason.

With both the e34s V8 and the Alfa's V6 running without an oil cooler at the moment, the oil temps reached on track are in the 125-150 deg C area. The funniest thing is both CSL's do exactly the same thing. Normal operating temp around 100, trackuse immediately sending it past 125, but a cool down lap will bring it right back. TWS has proven to be a major protection, one I would not like to miss.....
 

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Why is it that every Alpina built and Alpina modified BMW engine sports a big sticker stating "Alpina reccomends Castrol TWS 10w60" while those engines are nothing more then the same basic parts, bearings, pistons, hydrolifters etc. as in their BMW counterparts, just working a lot harder? They wouldn't reccomend that oil for no reason.
It could be related to the fact that TWS is a very expensive oil. What better marketing tool than have manufacturers state that it is compulsory in their engines.

For track use there is no doubt that it offers great protection but the question is whether it is recommended for the "everyday M5 user"; cold starts, highway driving etc etc

I use it but I do have my doubts

Lantz
 

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It could be related to the fact that TWS is a very expensive oil. What better marketing tool than have manufacturers state that it is compulsory in their engines.
That really doesn't make sense, as total production of Alpina and BMW M vehicles is so small it is of little interest to an oil manufacturer to cater a product for that market. It would be much easier to convince that car manufacturer of pouring something mainstream into their cars, and offering that car manufacturer a nice fat discount for doing so. Suprisingly, that doesn't happen, and the only two manufacturers offering serious driver BMW's swear by one and the same (out of all the more common choices) oil, being TWS. Who am I to doubt that reasoning?
 

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Discussion Starter · #13 · (Edited)
I'm one of the happy TWS 10W60 users, and will continue to do so. Not only in my BMW, but in a lot of other "intensively used" vehicles too. A "sportingly used" Alfa among others....

Why is it that every Alpina built and Alpina modified BMW engine sports a big sticker stating "Alpina reccomends Castrol TWS 10w60" while those engines are nothing more then the same basic parts, bearings, pistons, hydrolifters etc. as in their BMW counterparts, just working a lot harder?
You've answered your own question! Working harder!!

The original post pointed out that most engines run under 100 degrees at which the 10w60 oil is considerably less fluid than factory recommended weight oil would be.

You said you use it in hard driven cars and on the track, where the oil is often at 125+ degrees, a temperature at which the lower weight oils would not last as long before breaking down.

Your choice of this 10w60 is therefore wise if your cars are used in that temp range as often as you indicate.



Alpina cars often have higher compression, higher output engines that BMW factory cars, so they have more heat to shed, so are likely to also be running at above normal temperatures. Most are bought to drive hard.

I bet the maths done at Alpina suggested that the heavier weight protected the engines of the hard-driven enthusiast Alpina driver more than it caused non-optimum performance issues for the concours owners.


Regards

Ivan
 

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That really doesn't make sense, as total production of Alpina and BMW M vehicles is so small it is of little interest to an oil manufacturer to cater a product for that market. It would be much easier to convince that car manufacturer of pouring something mainstream into their cars, and offering that car manufacturer a nice fat discount for doing so. Suprisingly, that doesn't happen, and the only two manufacturers offering serious driver BMW's swear by one and the same (out of all the more common choices) oil, being TWS. Who am I to doubt that reasoning?
We are of course speculating here, but BMW recommends Castrol oils for all their cars just as Mercedes recommends Mobil oils for theirs. It makes sense that the M cars (being top of the range) would be recommended Castrols top of the range oil, the question is whether or not it is the appropriate oil in a real world situation. Ie where the car is occasionally driven to pick up kids, shopping etc. Very few people are at WOT all the time with an oil temp over 120 (which is the maximum limit according to the cars manual), so the question is whether or not its worth it.

Maybe a 10-40, 5-50 oil would be better for "normal" people. Perhaps the disadvantages of such a thick oil outweigh advantages when used in a street car.

Lantz
 

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Hi!
Hmmm... Interesting.
Just one observation. The oiltemp that the gauge shows is the temperature in the oilpan. Question: is this relevant?? as I suspect that the working temp at the friction surfaces (bearing shells, cylinder walls) under load is considerably higher.
If this assumption is somewhat correct, then lower SAE grade could possibly result in insufficient oilfilm and consequenty bearing failure under heavy load????

:cheers:
Sakke
 

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Maybe a 10-40, 5-50 oil would be better for "normal" people. Perhaps the disadvantages of such a thick oil outweigh advantages when used in a street car.

Lantz
Perhaps. Knowing how much of a heat trap a city-run S38 is I wouldn't take the chance though.'

Once came across a CSL running on 5w30 Longlife. You do not want to know what that sounded like on startup!
 

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What an interesting thread. I've been using TWS 10-60 since last year when I went to the ring having used Magnatec 10-40 before then on the recommendation of Munich Legends. I too have noticed that oil consumption is very much reduced.

The enlightened opinion seems to be that my motor will be better off if I return to using Magnatec. Is this right?

:cheers:

ralph (vadas1)
 

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The oiltemp that the gauge shows is the temperature in the oilpan. Question: is this relevant?? as I suspect that the working temp at the friction surfaces (bearing shells, cylinder walls) under load is considerably higher.
Good point you make on variable temps in the engine.
Hence the advantage of using the Group 4 base oil (PAO) based TWS, rather than a Group 3 synthetic like a 5W30.

One point on leaking seals. Some upper end lubricant products may contain small quantities of esters. These cause seals to swell, thereby limiting leakage of gaskets, seals etc. A lubricants is more than just its viscocity characteristic.


I've picked the brains of many of the Castrol technical boffins( one advantage of working for them for the last 17 years). Without exeption they recommend the TWS or RS (10W60)products in high performance applications.
Of course, in exeptionally cold climates (like Canada/NA, parts of Europe), you have to run the thinner product in winter, the start up viscocity of the TWS being just too high.
 

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2 weeks ago this thread came on in the E39 section (http://www.m5board.com/vbulletin/showthread.php?t=113309&page=3). By reading DouglasABaker posts things came up clear for me (pressure vs temperature). If u use a thin oil at higer temperatures and your pressure drops it wouldn't be right to use a thin oil. But if it stays at a good pressure the oil deliverance is good enough to lubricate the engine parts. The whole thing is that there is enough oil to deliver at a certain temperature (dependend on state of oil pump and capacity).

I've seen engines internal pictures and engine parts myself that run on TWS, and have to admit that its scars me allot. New camshafts that are already damaged after 30k km, the color that it leaves in the cilinderhead (allthough that might not "hurt" the engine I don't feel good about it)

The other thing I asked myself: why a S38 shouldn't run on anything else than 10W-60? Nowadays engines are so small and powerfull in comparisson to the S38. Why don't they need a high viscousity oil? Probably because not only engines are better engineerd, also the (synthetic) oil. Must be the reason why BMW stoped updating there oil list in TIS (must be a heck of work). For instance the Alpina 4.4 V8 recomends a 5W-30 oil.

All comes a bit down "Use what u and your engine like and what you have experienced".
 

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I agree with others this is an interesting thread.

Since the rebuid last year I have been looking at which oils I run and have alsi been running TWS 10w - 60. The oil consumption, never great, has dropped even more to the level that I am almost not having to top up in between oil services, which are now carried out every 3000 or so miles

The Alpina, a 4.8, is being run on the standard and Alpina recommended oil which is very thin - 0w - 30.

I think that all this says is that, within reason you need to pick an oil that both suits the driving requirements, the environment, the engine and the recommedations.

While the M5 is with me I will continue to use this oil.
 
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