Originally Posted By: OVERKILL
Originally Posted By: CATERHAM
With passenger cars the technical reason for the 0W-20 grade first being specified was to deal with the
increased wear in hybrid engines with Toyota and Honda. Remember the Prius was first spec'd for the 5W-30 grade.
To quote Nippon Oil who worked with Toyota and Honda to develop a suitable "hybrid oil";
"increased wear resulted from the constant on/off action of the engine, thicker oil will not be able to warm up (to temperature) properly. This could lead to unnecessary damage and wear. 0W-20's low viscosity is essential..."
I remember some other Japanese documentation talking about the wear issues resulting from the same push for thinner oils, I believe it was Honda? Also, the thinner oil isn't going to get up to temperature any faster either, it will just be closer to the desired viscosity than the 5w-30, which, in this specific application, sounds like it may be beneficial. However, as I said, anything pertaining to wear is engine-specific and this is a very specific application. Traditional warm-up does not resemble this duty cycle and there are numerous papers citing the primary source of wear during warm-up being start-up enrichment and the various expanding components like the out-of-round pistons.
For example, a document from the SAE:
http://papers.sae.org/600190/
Originally Posted By: SAE
Studies in laboratory engines equipped with radioactive piston rings show that wear is highest during a cold startup.
Corrosion by condensed combustion products is responsible.
Engine operating variables and additives in fuels and motor oils influence corrosion and, therefore, startup wear. Long shutdown periods, low engine temperature, and high intake-air humidity increase wear. In fuels, antirusts offer some control; for example, an amine dialkyl phosphate eliminates 40% of the wear. In motor oils, detergents are the most helpful ingredients; barium salts of organo-phosphorus compounds or sulfonate-phenates lower wear 30%. But, taken together, antirust in the fuel and detergent in the motor oil do not reinforce each other.
Ample room remains for further improvement. Strong polar compounds that chemisorb and form tenacious protective films on metal surfaces do the best job. Particularly valuable would be fuel additives and motor-oil additives that work better together.
You will note that they do not suggest going to 0w-20 as a solution
The SAE paper is suggesting 'all or most' of cold startup wear is
corrosion wear, not adhesive wear.
If so, does it mean adhesive wear in cold startup wear is insignificant or negligible , all the more so for hybrid car engines ?
Was the increased wear in hybrid engines (in Toyota and Honda) quoted above, mainly or solely corrosion wear, and not adhesive wear?
Originally Posted By: OVERKILL
Originally Posted By: CATERHAM
After a couple of years and the durability of this new engine oil was established, the
reduced wear and fuel economy benefits was seen to be beneficial for all engines so Toyota, Honda and others started specifying the grade for non hybrid models as well. The rest as they say is history.
I think it was Shannow who provided the documentation that stated "acceptable" levels of wear with this lubricant in the applications it was back-spec'd for, not improved wear protection/performance. I'll let him address that with you though as you two have a bit of a history on that one.
Could the 'claimed' reduced wear on Toyota and Honda engines using Nippon Oil/'Hybrid oil' are reduced
corrosion wear (and not reduced adhesive wear) being overcome with stronger 'anti-corrosion' additive package in hybrid oils, where viscosity of oils play no roles whatsoever ?
Shannow has a good point in suggesting relatively lower oil viscosity causes increased
adhesive wear, though 'acceptable' to some parties .... for whatever dubious reasons.
