Originally Posted By: CATERHAM
As if you would know.
Right back at ya. As if YOU would know! LOL!!! Glad to see that your absence from the board hasn't reduced the level at which you are willing to sling mud though
Originally Posted By: CATERHAM
It's an indisputable fact that the principal limiting factor determinimg how many rev's one can safely use without incurring increased engine wear during warm-up is the actual operational viscosity of the oil.
Got a link to some supporting documentation? Sorry if I don't take your word for it being an "indisputable fact"
Originally Posted By: CATERHAM
During warm-up the coolant may reach low normal temp's but the oil in the sump can easily lag by 80 degrees F even at room temperature and more at lower ambient starting temp's.
Yes, unless one has heat exchanger that is heated by the coolant, which many modern examples have.
Originally Posted By: CATERHAM
There is a maximum operational viscosity which decreases as rpms increase to provide the required volume of oil flowing in an engine to provide adequate lubrication. The principle is of course well established in racing, which is why so-called 0W-2 and 0W-5 oils are used when sump oil temp's barely get above 100F.
Lighter oils are often used in qualifying and sprints where oil temps won't get high enough and subsequently the potential for power loss due to increased viscosity is real. NASCAR does the same running ultra thin qualifying oils that are then swapped out for heavier oils for the main event (for durability). It is about getting the best qualifying time there, not about the oil volume at 7,000RPM being an issue.
However, we are talking about street cars here, not qualifying for NASCAR or Unicorn racing oils used in engines that are frequently rebuilt.
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
Originally Posted By: CATERHAM
For those that recall, the originally specified 0W-20 grade was often called a "hybrid oil" as that was the only cars it was originally spec'd for.
The big advantage of the Japanese 0W-20s was their very high viscosity index's of 200+ with a KV40 under 40cSt. TGMO 0W-20 was/is nominally 37-38cSt vs 58-63cSt for a 5W-30 and 47-49cSt for a 5W-20. This provided greatly improved oil flow on start-up and during warm-up when the oil was often not up to the fully hot normal temperature.
And the advantage of that, by extension, is increased fuel economy through lower drag and oil being closer to the desired operating viscosity. I have no issue with that, I do however have issues with your claims that it reduces start-up wear when the documentation I've seen does not support that nor even mention it as a contributing factor.
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.
Originally Posted By: CATERHAM
So you have two choices. If you are using a heavier low VI oil you must wait for the oil to heat up and thin out sufficiently to use higher rev's or you can use a lighter higher VI oil in the first place.
Well, that brings me back to my 2nd point regarding some documentation to support that claim. I've cited the SAE so far, can you please provide something equally credible to back this please? Thanks.
