I found this info at a very large John Deere construction equipment company website (for what it's worth):
Will changing brands of oil cause my engine to use oil?
When upgrading to Torq-Gard Supreme Plus-50 oils following use of oils other than Torq-Gard Supreme Plus-50, little difference in oil consumption rate should be expected. A small percentage of engines may experience a noticeable change in oil consumption rates. Increased oil consumption rates may be due to several of the following factors.
* The previously used oil product may have built-up deposits on internal components.
* When introducing a premium performance oil with different additive systems which contain additional detergents, dispersants, anti-wear and antioxidants, there are different chemical reactions occurring in the deposits already established.
* The time required for the engine to regain previously observed oil consumption rates with the new oil may vary from one to three normal drain intervals. This phenomenon is not unique to John Deere engines and oils, but is commonly reported for competitive engines when switching to competitive premium oils.
Why do some lower grade oils exhibit temporary reduction in oil consumption under certain circumstances?
Torq-Gard Supreme Plus-50 contains a high performance antioxidant which, along with the other additives in a balanced formula, results in the oil remaining in the specified viscosity grade throughout the recommended drain interval. Universal engine oils with API performance grades CD, CE, or CF-4 do not provide this oxidation resistance, resulting in more rapid thickening. Oxidation makes the oil more viscous (may result in temporary reduced oil consumption), resulting in a higher amount of deposits which increases the likelihood of excessive wear and shortened engine life.
While the information presented above addresses John Deere Torq-Gard Supreme Plus-50, engines using other premium priced specialty engine oils (supplied by OEM's and others) have exhibited the same characteristics.