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).
Issues of fuel gum formation in cars stored in showrooms or garages and recommending procedures to prevent it.
| Identifier | ExFiles\Box 103\5\ scan0163 | |
| Date | 16th February 1939 | |
| W/S. (G). BY.2/G.16.2.39. RE: STORING CARS IN SHOWROOMS OR GARAGES. I have had an opportunity of discussing the above matter very fully with Mr. Duff of the Shell-Mex Co. He confirms my view that the basic cause of the trouble is the fact that practically all fuels today are produced by 'cracking' the heavier forms of mineral oil, a procedure which has become necessary in view of the large and increasing consumption of petrol. The effect is that certain somewhat unstable components are produced during the 'cracking', which in the presence of warm air and humidity are oxidised to form a kind of liquid gum or laquer, which remains in solution except where the surface of the fuel exposes it and where it comes in contact with the tank; at the lines of attack with the surface of the fuel with the tank this gum dries out and forms an insoluble laquer, which can then only be re-dissolved by some entirely different liquid, such as :- (a). Acetone. (b). A solution of caustic soda. as previously explained to our people at N. by the Shell representative. One of the points I was particularly keen to discuss with Mr. Duff of the Shell-Mex was the length of time which was likely to cause trouble. His view is that if a tank had a reasonable amount of fuel in it, so that it was more than half full, no danger would occur within three months, but this does not quite line up with our experience on a Bentley car which GWH.{George W. Hancock - Head Chateauroux} had at N. where the car had not been in store more than about two months, and yet directly the car was used, and this would obtain in any case where the fuel had stood for a longer period than three months, the solidified gum was deposited on the butterfly throttle and the whole of the choke chamber in the form of a thick varnish, and since once the gum is deposited on a surface it can only be removed by washing off with Acetone in the case of aluminium, by caustic soda where aluminium parts are not used, but it is most important to avoid the cause of such treatment. I would therefore suggest that where cars are likely to be in a warm atmosphere for a period of six weeks that we empty the tanks or alternatively completely fill them. If the car is to be in store for two months or more, then I think the only remedy is to empty the tank before storing the car. | ||