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Old Jul 15th, 2018, 11:47   #15
AndyV7o
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Last Online: Jun 21st, 2021 21:47
Join Date: Jun 2018
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64000 dollar question - would a 0-30 kill the engine, and if so, how? Am interested to better understand, if possible.
*referred to this thread by another member*
Yes, I've read a good deal about oil, including that, but it doesn't answer my question as to whether a 0-30 would be deliterious to an engine which specced 0-20. Any thoughts on that?
Hypothetically putting aside all the other oil specs, I can't see how the slightly thicker oil would be directly damaging to the engine, but it would put greater load on the oil pump drive and so damage the fuel economy.

Answer:
It largely depends on the particular engine and oil.
If you read in *this* thread noting talk and behaviour of the HTHS values...
The 0w20 volvo/C5 spec is exceedingly light, if you were to use a C2 0w30 youd probably get away with it ok, a B4 spec 0w30 would/could cause excessive oil pressure and reduced flow starving the engine of oil. The saps of the spec also need to be considered, too low=engine wear, too high=dpf death (figuratively speaking)
Its not simply about xW xx in this day and age.

'I used to run Prii, where 0-20 was specced as part of the drive to lower internal friction and improve efficiency.'

Answer:
Its the drag which is reduced, and the base oils used/needed to make these oils by nature tend to have a better film strength if the crank journals etc manage to push through the hydrodynamic 'cushion' of oil. Its not friction which is lowered per-se (though of course drag is largely down to onternal friction within the oil itself)



The thing is, engines designed for these light oils have exceptionally tight tolerances in order to use them, which makes them even more intolerant of incorrect viscosity/hths
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