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The results of LPG motor fuel service tests in city busses of the Wichita Transportation Company are given which indicate that the inclusion of appreciable percentages of propylene in LPG motor fuel had no detrimental effects on the operation of city bus engines. Comparison tests between test fuel containing 15 per cent propylene and the fleet LPG motor fuel were conducted in six city busses operated for approximately 25,000 miles each in regular city route service. Evaluation of results in terms of change in Knock-limited spark advance during the test period and visual inspection of combustion chamber deposits were the basis of the conclusion that LPG motor fuels containing 15 per cent propylene afforded wholly satisfactory performance in this city bus service.

An investigation has been carried out under conditions comparable to normal engine operation to ascertain the effects of an additive such as nitromethane on the power output, fuel consumption, and efficiencies which result therefrom. It has been learned that nitromethane can increase power output by as much as 13 percent on an indicated or gross basis when added to methyl alcohol and by 7 percent when added to a benzene-isooctane mixture in concentrations of 20% by volume. By so doing, the indicated specific fuel consumption increases, but contrary to expectations, so does the indicated thermal efficiency. The results from the benzene-isooctane blend were comparable to those from the methanol in all respects except for the increase in power, which was not as great. The amount of nitromethane which can be added to a given fuel is a function of its tendency to bring about preignition in the engine.

No profound or basic discoveries eliminating wear of the subject parts are reported in this paper, but data and observations on some speculative aspects are presented. The data offered is, in itself, largely inconclusive, but may enable others to view their data from new angles and may inspire some new approaches to solution of old problems. It is shown that wear rates are subject to wide and unexplained variation. An analysis of possible factors on this variation is made. Is wear increased by extremely low oil consumption? Some new data on this old question is offered. Finally, an analysis of characteristics of the new engines is made, indicating that we may be facing some new problems.