From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Improvements in motor oil, focusing on valve sticking, carbon deposits, and viscosity.
| Identifier | ExFiles\Box 145\2\ scan0057 | |
| Date | 1st February 1935 guessed | |
| No. 3. traction treatment is seen in the almost complete elimination of the green appearance of the oils when examined by reflected light. This is due to the removal of those impurities that accentuate sludge formation and valve sticking. The new oil when used appears to darken rather more quickly than the older oils, due to its initially paler colour and the absence of the masking effect of those impurities that give a green fluorescence. Analyses of used oils show very definitely that the Clearosol Process oils are in much cleaner condition after extended use. Valve Sticking. Improvements in design, materials and manufacture of modern automobile engines have considerably reduced the valve sticking difficulty. Nevertheless, it still persists in a number of cars. The new grades of Mobiloil offer considerable assistance to engine builders in this direction. It is generally agreed that pure mineral oils of high quality give the greatest freedom from valve sticking. The new oils are 100% mineral and of greater purity than would have been considered possible even a year ago. Carbon Deposits. An obvious result of these changes is a definite reduction in carbon deposits in combustion chambers, in addition to cleaner crankcase conditions. While carbon deposits on pistons are not a serious factor in modern engines when using the previous grades of Mobiloil, these new oils give decidedly cleaner combustion chambers and better valve and seat conditions. Longer running periods between top overhauls, together with better maintenance of engine performance over big mileages are to be expected by the user. Improved Viscosity Curves. The following table shows at a glance the benefits of the new Mobiloil (Clearosol Process): SUMMER GRADES. | Mobiloil "BB" (Clearosol Process) | Average High Grade Motor Oil. | Ordinary Motor Oil. | |---|---|---| | Viscosity @ 70°F (Redwood) | 2250" | 2600" | 3600" | | Viscosity @ 200°F (Redwood) | 83" | 80" | 80" | | ||