WHICH OIL FOR E39 M5??

Sorry to go on about this guys, but I'm totally confuesd now and
a little concerned, apologies for being thick !!!

So which oil should I be using in my 2001 M5, cos my Dealer
suggest Castrol TWS 10-60 and this oil is even listed on the
BMW car Club website
www.bmwcarclubgb.co.uk/sections/mpwr/M5s/M5E39Extra.htm

Can anyone point me in the direction of the BMW bulletins
regarding the oil type (are they for public viewing) so that I can
see for myself.

Cheers Steve

Thanks for the info. It is Damon Hill who Ive been using,
needless to say I'll be talking to them about this !!!

Hey Guys, all my buddies at the Nuerburgring are using TWS 10-60 in their e39 M5. So are all the E46 M3 guys.

TWS is a real ester based oil (like Motul). That is also why it is a bit more expensive than other oils.

No engine is so special that it needs only 1 particular brand of oil. Check Porsches list of approve doils for new and older models e.g.    It is also more than ok to change the oil before the normal oil change interval comes up if you so desire.  Some things you do not have much ability to control (short of changing oil) -- like acid content -- for this you have oil additive packages. But somethings like fuel content in the engine oil is detected by the ECU.   I have it somewhere in my documentation for MSSxx ECUs where they specifically talk about fuel in oil detection.  Since they are trying to detect this, this should tell you what the importance is?

John

I am aware of BMWs recommendations, and in that recommendation TWS was never EXCLUDED as an oil that might HARM the engine.

changing piston to sidewall clearance is hardly going to be a determining factor whether the oil is harmful or not. They trying to reduce blowby and oil consumption.  But, if you left TWS in there eventhough the oil consumption is down, that will not cause harm.

on race track we are generally interested in keeping oil temperature low, because too high oil temperature is bad for things like rod bearings. when these get damaged, you will see oilP fall (if you have a guage), then oil temperature will rise further and soon you will have a complete bearing failure.

I select an oil because it is good and for my intended use. I am not too religious about it though. I know a little more about engines than what is stated in the owners manual :)  but only a tiny bit.

John

 

 

There seems to be a little confusion here (not on the recommended oils as this is stated by the BMW TIS and in handbooks, as correctly stated by Stephen B) over quality.

Castrol RS 10w-60 is a hydrocracked (highly refined mineral) oil and not of the best shear stability or quality.

Castrol TWS 10w-60 is a different formulation with higher HTHS numbers and NOACK volatility % due to its synthetic basestocks which are likely to be the minimum poly alpha olefin and at best a pao/ester blend.

The point is that neither 10w-60's are BMW LL oils and never likely to be as they don't meet BMW's criteria viscosity-wise (0w or 5w, sae 30 or 40).

Whilst it can be argued that 10w-60 is traditionally a grade for extreme use (based on the theory that shearing in use will mean an sae 60 will thin to an sae 40 over a couple of thousand miles of hard use) the old school way of thinking does not apply with modern synthetics.

Modern synthetic basestocks are incredibly thermally stable with very small amounts of VI improvers added meaning there is no where to shear back to. (see below explanation)

The biggest problem is the use of an oil that's very thick (as thick as some gear oils) which can mean more friction and heat leading to more engine wear, lower fuel consumption and a lower power output due to oil drag when it's not necessarily required.

Stepping up the viscosity from sae 30 or 40 to sae 60 is only warranted if oil temperatures are excessive (above 120degC) and then an sae 50 (proper synthetic race one) will adequately handle up to around 145degC for prolonged periods.

Granted in some models 10w-60 is required due to design but not for all applications by any means.

Why do oils lose viscosity with use?

 

Viscosity Index Improvers.

 

An oils viscosity will decrease as the engine temperature rises. Viscosity Index Improvers are added to reduce this thinning. They are a key addative in the production of multigrade oils.

 

VI Improvers are heat sensitive long chain, high molecular weight polymers that minimise the viscosity loss of the oil at high temperatures. They work like springs, coiled at low temperatures and uncoiling at high temperatures. This makes the molecules larger (at high temps) which increases internal resistance within the thinning oil. They in effect "fight back" against the viscosity loss in the oil.

 

"Shearing"

 

The long chain molecules in VI Improvers are prone to "shearing" with use which reduces their ability to prevent the oil from losing viscosity. This "shearing" occurs when shear stress ruptures the long chain molecules and converts them to shorter, lower weight molecules. The shorter, lower weight molecules offer less resistance to flow and their ability to maintain viscosity is reduced.

 

This shearing not only reduces the viscosity of the oil but can cause piston ring sticking (due to deposits), increased oil consumption and increased engine wear.

 

Like basestock quality, VI Improvers also vary in quality. As with many items the more you pay, the better the finished article and more expensive, usually synthetic oils are likely to incorporate better VI improvers. All other things being equal the less VI improver an oil contains, the better it will stay in grade by resisting viscosity loss. 

 

Which oils require more VI Improvers?

 

There are two scenarios where large amounts of these polymers are required as a rule.

 

Firstly in "wide viscosity span" multigrades. By this I mean that the difference between the lower "W" number and the higher number is large for example 5w-50 (diff 45) and 10w-60 (diff 50) are what is termed as "wide viscosity span" oils.

 

Narrow viscosity oils like 0w-30 (diff 30) or 5w-40 (diff 35) require far less VI Improvers and therefore are less prone to "shearing".

 

Secondly, mineral and hydrocracked (petroleum synthetic oils) require

more VI Improvers than proper PAO/Ester (Group IV or V) synthetic oils

as they have a higher inherent VI to begin with, this is due to

differences in the molecular straucture of the synthetic base oils

compared to mineral oils

 

It is a fact that many synthetics require significantly less VI Improver to work as a multigrade and are therefore less prone to viscosty loss by shearing.

Hope this helps,

Regards

Simon

When it comes to oil discussions it can become religious. If the purpose of this discussion is to go in circles, then Im not interested, simply because these usually end up no where. I put my money where my mouth is and build up engines and track them. I do many things that are not recommended in your owners manual that you may or may not balk at, e.g. engine break in happens in less than a few hundred km.  I rev an engine over 8000 rpm with less than 100 km on the engine.  I also drop bottom ends to check the condition of rod bearings and swap new (motorsport) ones in even though the old ones optically apear in very good condition. So I am not driving the car and wondering what is going on in the bottom end without any sort of feedback.

On TWS:  it is a polar oil. AFAIK, only ester oils are polar.  It is a mistake to read too much into the "60" part of the 10w-60 designation.  This oil is NOT a 60 weight oil. It is based on a 10 weight oil. It just BEHAVES at 100C like a 60W oil.  This is key to understand.

So, you read a bit of physics and think: oh it is a 60 viscosity oil and therefore there is more internal molecular friction which must raise the oil temperature.  It doesnt work like that, nor is this seen in practice. You may trust me when I say that the engine itself under whatever operating conditions has far more effect on the oil temperature than the molecular friction in the oil!  In fact, if your engine is running too high oil temperature under track conditions, there is no oil that you can simply put it in it to lower the engine temperature any significant amount. You need hardware modifications to accomplish this. Im assuming a healthy engine, if you are getting metal to metal contact, then it is a non issue and you will not be driving for long under track conditions.

I would be concerned to run an engine over 120C on the track for sustained periods.  BMW Motorsport says that 125C is MAXIMUM engine oil temperature. Oil break down is obviously much higher than this temperature.  Can you get away with higher oil temp? yes you can, but the wear and potential for failure goes up.

Motorsport (racing division) does quite extensive modifications to increase cooling to lower both oil and water temperatures.  E.g. extra radiators, ducting and lower T-stat opening points (for lower water temperatures) and larger oil coolers and oil-water heat exchangers to keep oil temperature down. Oil coolers are run without bypass valves to eliminate any lag time -- they cool maximumm at all times as long as the car is moving. To get maximum power it is ideal to run the engine around 80 C water and 80-90C oil -- on a race engine. On a street engine we might rather see 90-100C oil temps as ideal. Just to make sure the oil gets hot enough to burn off things like fuel in the oil. On a race engine, the oil gets dumped, so fuel contamination in the oil is a non issue. On street engines it is enough of an issue that the ECU tries to determine (MSS62 and MSS54 ecus e.g.) the fuel content in the oil.  For similar reasons, when an engine has more blowby this is something that degrades the oil over time. When crank case gases are recirculated into the intake tract, this also causes problems with reduction of octane (by lowering it), increasing its likely hood (if significant) to knock -- therefore the ECU would retard its timing.  When you run tighter piston-wall clearances or have a better ring-wall seal (due to better rings, better run-in, or change of hone pattern) you usually get lower blowby.

My friends at the N'ring all use TWS. Does this mean this is the best oil to use? is it the only oil to use? of course not. But, it provides atleast practical experience that the oil is not bad, and this was my primary point.  If I go to the track, Im pretty sure Id follow their lead. But I also open the engine up from time to time to check things. I dont believe that there is any MAGIC involved.

As far as RS 10W-60 and hydro cracked oil -- I really have no comment. I was only trying to comment on TWS.

If you want to run a "long life" oil then go ahead, BMW approved it so there is no reason to second guess them right?

John

 

 

 

 

 

still looking... :)

but while looking I saw a few other things, Ill post here too:

-- the GTR was also using TWS in the latest 24h race at Ring. This oil also in GT3.

-- on race engine be VERY careful when making any assumptions why they may or may not use a light(er) viscosity oil.

-- on a race engine, you dont need a huge additive package which is what "long life oils" have. additive packages do nothing for your bearings, they just stabilize the oil. So this might be a consideration for someone that intends to run WOT for extended periods on track. If you are an environmentalist, perhaps it is important to you to keep the oil in service as long as possible. If you are primarily interested in your engine, changing oil based on your (track) use may have priority.

 

anecdote: in the late DTM days, BMW motorsport reached rpms up to 10500 rpm. They switched to a lower viscosity oil, I dont know the type or the rating but I was told by BMW motorsport this was so. It was probably a special formulation not available to the mass market. If it is of real interest, I can ask on tuesday at Motorsport the exact spec just so we know. The reason this came up was because I was investigating differences in 2 different DTM cranks.  One had 1 oil supply per rod journal and the other crank had 2 supplies per rod journal.

This might be obvious to some of you guys but not to all, and since its important, let me explain: when we go up in the revs we like to ensure high oil pressures. The usual rule of thumb is about 1 bar per 1k rpm. So at 8k rpm that would mean 8 bar oilP! This is not really easy to achieve and requires modification of the oil pump (we are talking about a wet sump engine). Obviously, this also cost a bit more loss which you can add to your over all power loss budget for your engine. According to BMW research papers, increasing oil pressure up to about 8 bar sill makes sense, but after that it does not make sense to further increase oilP. IOW, even with 12 bar oilP you could not protect your engines from rod bearing damage at very high rpm; you have passed the point of diminishing returns.  The solution to this problem is to increase the number of oil supply passages at the bearings, and it can not be done in just any fashion (various configurations are possible, not all effective).  BMW Motorsport did exactly this on the late DTM cranks, and when this happened they no longer required such high oil pressures nor high viscosity because they have increased the fluid flow or lubricity.  This little change made the price of the crank jump from 2000 euro to about 3500 euro :)

John

 

 

 

 

 

harvard468 wrote: Adam, I'm very surprised at this because last July (2004) when I was getting nowhere I rang Damon Hill and they got it right as did Dick Lovett in Bristol!! Maybe you got a different Service Agent who didn't bother checking his tech specs! Regards STEPHEN B

 

Stephen

I contacted Damon Hill on Friday, after questioning the 10-60 the chap I spoke to did go and check it out, he phoned me back as good as gold and confirmed that the 10-60 is not the correct oil. As you say perhaps its down to different service agents.

At least I now know which is the correct oil and I know that Damon Hill also know - its a relief !!!

 

Thanks again !!!

Yep, your free to take your own oil.

Cheers

Simon.

Yes!!!  Unless they had misfilled it with TWS at the last oil change in which case it won't make any difference!  Look in your manual!

Stephen B.