You are welcome,bigjl!
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The bad news is that nearly all 15/40's are designed for trucks and that means they have to be cheap, so the quality of their add packs is not so good and not many are true long life oils as a result.
Skyship,I beg to differ on this one- the table at the bottom of this document says just the opposite(you will see that A3/B3/B4 performance level is achieved at lower additive package ratio in the same basestock):
HiTEC 8799B
WBoer- Not sure about what the engineer you spoke to might have had in mind(better boundary lubrication protection due to heavier additisation?Harder to "rupture" oil film in the sense of the two quotes below?). What one usuaIly hears is that synthetic oils have stronger oil film than their mineral cousins.
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The molecular structure of many synthetic oils also gives them higher film strengths than petroleum. The oil film keeps two moving parts from rubbing against each other, and higher film strength enables synthetics oils to withstand heavier loads, faster speeds, and to better prevent wear. (Synthetics, Mineral Oils, and Bio-Based Lubricants - Chemistry and Technology, CRC press) etc.
MolaKule says in one thread:
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Film strength's are dependant upon viscosity, but that is not all that is involved. Consider these items. If the molecular chains (molecular bonding and chain arrangement) are much stronger and more consistent, then the fluid has a higher film strength; synthetic fluids have stronger and more consistent molecules than do dinos. Synthetics are less likely to shear under high loads, maintaing hydrodynamic lubrication...
google: "film strength" synthetic site:bobistheoilguy.com
And OEMs would've recommended easily-obtainable HDEOs in certain high-performance cars instead of high-tech synthetics...
Not that the hdi or tdi would blow in smoke if mineral 15w-40 were used, but they're not the optimal choice long-term. And do not fit in OEM recommedations (at least not in DW10td's case- no matter how simple and rugged the engine is).I'd hate to hear a lifter tick in cold weather,change the (humble amount of 4.25l of) oil @ less than the "severe use" prescribed interval(15K km.), lose some fuel economy in winter or lose sleep over the turbocharger longevity..or cat health...or proper EGR operation