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).
Outlining the required properties of oils for the Luvax-Bijur chassis lubricating system.
| Identifier | ExFiles\Box 27\1\ Scan019 | |
| Date | 23th January 1929 guessed | |
| MEMORANDUM REGARDING OILS FOR LUVAX-BIJUR CHASSIS LUBRICATING SYSTEM. As all the oil goes through a filter pad of dense wool felt ¼" thick intended to catch any solid particles, or masses of metallic stearates, or suspended matter, such as Graphite, or masses of tallowy substance, it is essential that the oil should contain no suspended foreign matter, but should be a homogeneous fluid capable of passing through a felt filter without depositing thereon any solid residue. Other things being equal, it is preferred to use a clear oil having the natural yellow oil colour in preference to a very dark or black oil, for the reason that substitution of incorrect oil is more difficult when the owner-driver is accustomed to a correct oil having a clear appearance. If he has been accustomed to a clear oil, he is likely to refuse a black oil, and it is feared that black oils are likely to contain free foreign solid matter. Except for the above there is no objection to a black oil and some black oils answer the purpose admirably. The oil (at 20ºF) must not have a consistency greater than that of ordinary vaseline at 60ºF - it is desired to have the oil retain some mobility at plus 20ºF.{Mr Friese} Oils that do not retain fluid at freezing point will not answer. The oil should have as high a viscosity as possible consistent with the above requirements when measured in Saybolt seconds. Engine oil at 100ºF is believed to have a viscosity of between 300 and 600 Saybolt seconds. Less than 600 Saybolt seconds is too low for purposes of chassis lubrication. Very much higher viscosity is useful. For instance, there are oils which remain slightly mobile at plus 20ºF whose viscosity at 100ºF is 1800 Saybolt seconds, and certain oils are obtainable having the above desired qualities whose viscosity at 100ºF is 2500 Saybolt seconds. This paragraph may be summed up by saying it is believed that many engine oils will answer the XXXXX purpose, but certain brands are likely to be preferable to others owing to their higher viscosity and better lubricating qualities. | ||