Abstract: In a Type 2 engine, a valve deactivation hydraulic lash adjuster (DHLA) in accordance with the invention replaces a conventional hydraulic lash adjuster in the train of a gas-exchange valve in a compression-ignited engine. In a Type 3 engine, a similar DHLA is disposed within an articulated rocker arm which is made selectively competent (valve activating) or incompetent (valve deactivating) thereby. A solenoid valve within the assembly diverts hydraulic fluid between support and non-support of a piston slidably disposed in a housing and terminating in a ball head. The valve is force-balanced. The preferred hydraulic fluid is diesel fuel, allowing for smaller diameter passages and cleaner operation than in prior art systems, eliminating the need for an accumulator chamber and accumulator piston as in the prior art. An alternate version of a type 3 engine having a DHLA, in accordance with the invention, is also shown.