I don't recall this being the case before the April patch, but it now looks like infantry and artillery now consume oil. Why? I find this personally annoying, as the upgrade path from musketmen to infantry is already pretty wide (and for bombards -> artillery), but also it makes no sense to me. If anything, these units should consume iron (to cast their gun barrels), which is already basically obsolete by the renaissance era. Or perhaps iron and niter. But oil? Where is the logic in that?