Various approaches are described for operating an engine in a vehicle having variable valve operation for an intake and/or exhaust valve of the cylinder. In one example, a method comprises delivering a first fuel to a cylinder of the engine from a first injector; delivering a second fuel to the cylinder of the engine from a second injector, where a composition of at least one of the first or second fuels varies; and adjusting the variable valve operation responsive to the varying composition and further based on variation in the delivery of the first or second fuel.