As you seem to know a lot about oil:
what do you think about Motul 300V 15W50 ???
I do use it in my E24 /// M6 for more than 12 years now ( change oil every year / more or less 5000 km/year ) and it doesn't eat even a cl of oil.
Can I use it on a S38 B38 with same utilisation, or better Mobil 1 10W60 ? ( BMW mainteance book says 15W50 )
thanks in advance for your return..
The lubrication requirements for the M88/3 were written in a time when there was some awareness of fuel-efficiency and emission reduction, but as there were no standards mechanical engineers could draft the lubrication requirements according to their own needs. These requirements were primarily aimed at optimizing a cars performance whilst sufficiently protecting its engine. Even when technology has progressed in the last thirty years, newer doesn’t necessarily mean that it is an improvement for all cases, especially since the automotive-and lubrication industries have to meet environmental requirements first.
We know that safety comes first…… well the same thing applies for environment. Its environment first and then the rest.
Now, if we enter the time machine and go back to the 1970’s and early 1980’s era, the latest AI standard was SF and availability of multigrade oils was mostly limited to SAE10W, SAE 15W and SAE20W base-grades. The manual addendum for the E28 M5 only approves an 15W40 that is compliant to API SF/CC/CD standard. Nowadays such oils are mostly available in your local hardware shop as a low budget brand, but if you take a closer look into the SAE requirements for SAE40 grade, we can see that there specific sub-groups exist for SAE10W and below and SAE15W and above.
The main difference is the requirement for the High Tension and High Shear value (HTHS). HTHS is the measured dynamic viscosity at a predefined high load and high temperature (150°C). Even when the market sees a 0W40 and 5W40 as high-tech products (because of their manufacturing processes and complex polymer additives to obtain the temperature stability), the minimum requirement for HTHS is 3,5cp for 0W40, 5W40 and 10W40 oils whilst this is 3,7cp for a 15W40 oil.
This contradiction; low-tech versus higher HTHS is confusing as most people would imply that the higher-grade 5W40 and 0W40 would offer a higher level of protection. Nothing comes further from the truth.
Now let’s be strict: since 10W40, 5W40 and 0W40 oils were already defined in the late 1970’s and early 1980’s and to some extent were also available, why would BMW not have approved those grades ?
The specific requirement for an SAE15W40 and for the S38 up to 20W50 as well is clear. With the only difference being the minimum value for HTHS, one might safely assume that HTHS for the M88/3 and S38 engines should be more then 3,7cp !!!
Many owners have used a ‘high tech’ 5W30 oil for their S38 powered cars. With a minimum HTHS requirement of 2,9cp for this grade, one can safely assume that the integrity of the oil film is not maintained under a high engine-load/speed.
Since Motul’s Competition 300V 15W50 grades from Motul as a HTHS rating of 5,33cp, there is no concern for using this oil in an S38 / M88 application.
One remaining issue of concern is the content of the anti-wear additive ZDDP that is normally specified by the content of its main elements zinc and phosphor. These elements protect the engine in area’s were boundary-mode lubrication occurs. When this occurs, metal to metal contact will occur. The area of concern in general in the cam-lobe interface.
ZDDP is detrimental to the longevity and functionality of the catalytic converter, hence why the automotive industry was forced to lower its content gradually in the last 10-15 years. For modern engines such as the M54/S54/S85 this is not an issue as they rely on roller cam-guides to avoid boundary-mode lubrication.
It doesn’t necessarily mean that our S38/M88/S14 engine require the ample amount of ZDDP as for instance the classic US V8 engines with solid rocker/lifter constructions, but todays trend to lower the ZDDP to levels below 800ppm for phosphor and therefore also zinc imposes a serious risk to older engines as well.
The reason why I have made the switch to Mobil1 EL 10W60 (at least for the non-catalyst M88/3) is the ample specification of 1300ppm on phosphor. This is more than plenty for an S38/M88, so a bit less is acceptable and for the catalyst S38/S14 even preferable. But manufacturers generally do not specify for ZDDP. Mobil1 does that for 15W50, but Motul does NOT for the competition 300V 15W50 and LeMans 300V 20W60.
With all those oils being available and with so many opinions around, I needed an objective model to normalize the performance of specific lubrication product against the simple 15W40 grade that is prescribed in the M88/3’s manual addendum. Don’t ask me to disclose details about the algorithms and calculations as this has been the result of many months of work.
Mobil1 15W50: 126,0567
Motul Competition 300V 15W50: 124,3206
Normalized against the referenced 15W40 (100), both lubricants have more-or less the same performance. From this perspective, the switch from Mobil1 15W50 to Motul Competition 15W50 is IMHO arbitrary.
Mobil1 15W50: 102,0167
Motul Competition 300V 15W50: 104,143 (provisial)
Also the protection performance appears to be small, but please note that Motul does not specify the content of ZDDP in its datasheet’s whereas Mobil1 does. I have recently requested the same information for their 15W50 product and am awaiting an answer. However, until I know the exact details, I can only assume that the actual ZDDP content is low. Now, if hypothetically speaking, Motul Competition 300V 15W50 has the same level of ZDDP as its 20W60 sibling, it would perform 118,2504 against the 15W40 reference and that is significantly more than the competing 15W50 product from Mobil1.
The main contributor to that high performance is its ester base. However, bear in mind that Group V base-oils despite having excellent performance that at some points exceed those of group IV PAO’s by almost any account, also has some disadvantages; (1) swelling influence on gaskets and seals, (2) susceptibility to water and (3) high cost. These facts are the main reason why group V’s are only used in specific (racing) applications or mixed with group IV PAO’s to compensate for amongst others the seal-shrink effect of group IV PAO’s.
The exact formulation of a product is covered behind the curtains of Non-Disclosure Agreements and/or trade-secrets, but the sole reason to choose for a specific manufacturer because of using Ester technology is not good enough for me without a matching specification. Let me just say this, a high content of ZDDP is more important to me than using ester-technology.