Back in the late 70s and early 80s when I worked for a CAT Dealer, they send me to Peoria, Ill factory train on the 3406 truck engine. Never heard of the C-15. Must be the newer version. I been gone from CAT well over 20 years, a lot of changed engines. The 3406 and 3208 were popular back then for trucks. Ever seen the 399 industrial engine. A lot of offshore drilling rigs had em. I could tell a long story on that engine. To make it short, a rig mechanic mess with the governor and he didn't know what he was doing. The engine ran off and threw a rod. They claim it shook rig, it was 120 miles off the Louisiana coast.
D399 V16
1100 HP 1200 RPM