These are excellent questions:
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Originally Posted by richtate
Bob, my question is the characteristics of the multi viscosity oil. My understanding is the chemical additive to the oil will change the viscosity as temperature increases. Also this chemical will break down as it is used repeatedly. In this case taking a 0 weight oil to a 20 weight. But as noted, with 8K usage, the chemical break down could effectively be leaving the oil weight at a lower weight than the designed target of 20 weight when at operating temperature.
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My reading of the literature (Machinery Lubrication and a Nora Handbook) says that there are viscosity range extenders. These molecules curl or straighten as the temperature changes to extend the viscosity range. However, they are subject to 'shear stress' that over time chops them up.
Quote:
Originally Posted by richtate
How are you taking this into effect? Are you measuring the viscosity of the oil at temp?
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That is exactly why I send my oil samples off for testing and pay extra for a 40C and 100C viscosity test. This also gives a viscosity index. Sad to say, not every oil testing service (aka., Blackstone) offers the two-temperature, viscosity test. Ask before sending off your samples.
Quote:
Originally Posted by richtate
Is the difference really a viscosity comparison of less than 20 to 30 weight? That would not be giving the additive a chance, would it?
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I needed to know if my test protocol was sensitive enough to detect a change yet I also knew the additive in addition to claimed friction reduction also put a lot of varnish and gunk back in suspension. Suspended varnish and gunk is the liquid equivalent of smoke and increases friction. I am not expecting to see a measurable engine friction reduction until after the second change (and possibly pan cleaning.)
So to test my test, I compared 0W-20 with 8k service miles versus new, 5W-30 and found a measurable, 2% reduction in fuel burn. But it turns out I will also be conducting progressive measurements to monitor any gasoline effects.
This morning I left the NHW11 at home so it will warm-up during the day. By the time I get home, it should be in the mid-70s so my warm-up test will give good data. I will then fill-up the tank and drive enough to burn out the gas in the lines and park the car until tomorrow when I'll repeat the warm-up test.
Quote:
Originally Posted by richtate
This is great information as I'll be applying your findings to my oil choices, no doubt.
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You are welcome and that is what I so admire about Ecomodder, applied science.
Bob Wilson