The RS-11 was Alco's answer to the hugely popular Electro-Motive Geep. Alco had, after all, invented the road switcher: a multipurpose engine with great visibility fore and aft, capable of anything from slow-speed switching to full-throttle mainline hauling. And in the late 1940s and early '50s, Alco's pioneering RS-1 and RS-3 had sold well. But Alco's 1600 hp model 244 motor had acquired a reputation for unreliability, and the Electro-Motive GP7 and GP9, copying the road switcher concept, became the runaway best-sellers of first-generation diesels.
One wonders today if Alco's problem was really its motor or EMD's commanding sales lead. Back in World War II, EMD had been the only company permitted to manufacture road diesels, and shop crews nationwide had learned to service the EMD 567 prime mover. Perhaps a lack of familiarity led to lesser-quality maintenance of Alco motors; as evidence, Alco fans today point to the New Haven, an all-Alco railroad that got great service from its Alco fleet while others complained.
In any case, the RS-11 addressed the reliability issue with a new Model 251 V-12 motor, offering 50 more horsepower than the contemporary GP9. At least a dozen Class 1 railroads in the U.S., Canada, and Mexico bought the new engine after it was introduced in 1956. Some used it in passenger service with an optional train heat boiler. Later a low-nose version with better forward visibility was offered. But while the RS-11 was a good locomotive, the race had already been lost. Sales numbered in the hundreds while Geeps sold by the thousands. Some RS-11 orders were simply fallout from EMD's success - when they couldn't make Geeps fast enough, Alco got the overflow orders. While Alco soldiered on for another decade, introducing its Century series of locomotives, the RS-11 turned out to be the last Alco diesel that sold in significant numbers.