Viscosity Breakdown

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Sep 28, 2002
The same brand & batch oil in two vehicles, tested at approx. 1100 (eleven hundred) miles in each. Starting viscosity 0W30 = 11.30 Vehicle #1 = 10.20 Sulfur 20, Nitr.11, Ox 2 Vehicle #2 = 9.91 Sulfur 47, Nitr.11, Ox 0 All dilutions, and contaminants are zero, wear metals low or none. What caused the viscosity breakdown in a relatively short period of time?
Some engines are just simply harder on the oil, for many reasons. Higher rpms, different valvetrains, smaller oil capacities, higher oil temps, etc.
Well, on vehicle Number 2, your sulfur level was higher, so it possibly came from a different fuel or from different fuel/air mixing ratios, called stoiciometry. The increased sulfur probably created extra acids that caused viscosity shearing as well. Heat, mechanical stress, and chemical attack all cause viscosity shearing.
Originally posted by Bill J.: Would a higher compression engine shear back the viscosity faster?
Not necessarily. My LT1 engine uses 10.4 to 1 compression and doesn't hurt the oil much at all, due to it's low revving nature and pushrod design.
Molecule... Would a regimen of Schaeffer's Neutra #131 possibly be in order for these engines?
How about production variances between batches of the exact same brand and grade of oil? Or how about the oil analysis percentage of error? Maybe even both of these two variables combined.
Bill J, It wouldn't be a bad idea. This would clean any "left overs" from previous oils and or accumulations of acidic sludge. Neutra , Lube Control, or Auto_RX would clean just fine.
I was specifically planning on using the Neutra #131 as a fuel additive. Would fuel sulfur and nitration benefit from a sustained course?
I would try the Neutra or the Fuel Power in the fuel and see if either would bring down the Nitration. I am not sure if either would reduce the sulfation from the fuel, but it's worth a try.
Widman, thanks for the post. Both vehicles are burning the same fuel. Both are running efficiently with recent maintenance. None of my vehicles are low mileage, they range from 62K to 140+K. My take on the problem from reading various analysis directives, the 0W30 is the wrong viscosity. I will be moving up to 5W40 which is another acceptable weight. 15W40 is also an acceptable weight but only for strenuous towing, mountain driving etc in hot weather. I think the 5W40 will be fine in our climate. I'm using it in another vehicle now, and the oil will be tested but not soon. Based on having analysis done on three vehicles using 0W30 I will no longer use that weight, or for that matter 10W30 either.
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