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Oils - what do all the number mean?

Discussion in 'Bling and Appearance' started by Chairman, Jun 22, 2008.

  1. Foreword - Please feel free to contribute informed comment to this thread. If you have strong opinions on whether a bike should be run on 4-stroke, diesel, extra-virgin or baby oil, they'd be great conversation starters for another thread - not this one.

    With that out of the way, here's my question. The recommended oil for the MV Agusta is Agip Racing 4T 10W-60. Sadly, it's as rare as rocking-horse shit and is so pricey it might be cheaper to replace the engine rather than the oil.

    I've been researching alternatives. I looked at Penrite (always very happy with it in my low-revving singles) and came across their SIN 5W-60 and SIN 10W-70

    Hmm. 5W-60. Might be a bit thin when cold. 10W-70. Might be a bit thick when hot. So I dug a bit more, and found some specs. Here's a comparison

    										Agip		Penrite		Penrite
    									     10W-60	 5W-60	       10W-70
    Vicosity @ 100C (mm/s or cSt)		23.5		24.1		29.2
    Vicosity @  40C (mm/s or cSt)		160		 157		215
    Viscosity Index							177		186		176
    I gather that mm/s and centiStoke are equivalent units, so the numbers can be directly compared.

    So AGIP 10W-60 seems to match Penrite 5W-60 on the specified parameters, but Penrite has a higher Viscosity Index (which, I gather, is a good thing). On my reading the Penrite 5W-60 should do the job just as well (assuming its not full of other nasties in the additive package).

    Am I right?

    http://www.penrite.com.au/files/HBPH2CIKGF/SIN EngineOil 10.pdf
    http://www.penrite.com.au/files/JZA0LN6URD/SIN EngineOil 5.pdf
  2. The Penrite has a higher viscosity index simply because it has a lower change in viscosity with temperature (ie 24-157 instead of the 23.5-160 of the Agip) - and yes the higher the number the better since it means the oil is more stable/consistent with temperature.

    Oils with a high viscosity index usually are only achieved with either a full-synthetic, or a semi-synthetic that is pumped full of additives. The downside with the latter is that it tends to mean the oil breaks down pretty quickly so needs to be changed often. Depending on the engine this can sometimes make the expensive full-synthetics cheaper.

    Oh and I know Castrol has a full-synthetic 10W-60 (Edge Sport) that's usually pretty easy to find, not sure if it's suitable for bike engines though. May be other car oils out there that could be worth a look as well if you can find similar specs (actually amazed such data was actually readily available).
  3. It is not suitable for wet clutches, BTDT.
    There are plenty of automotive and diesel oils with teh same additives and qualities of motorcycle oil (some easily surpass the motorcycle oil specs too), just need to spend teh time to look.

    Regards, Andrew.