Steam and water cleaning older engines with fuel injection is always a little bit risky. Humidity getting into some parts can make re-starting a challenge. Note that we don't speak of permanent damage, only that you'll have to wait or dry those parts with compressed air. If you do this yourself, there's no problem, but at a garage, when other cars queue up behind you, it can be bothersome.
Citroën specifies Purflux oil filters but there are other manufacturers producing similar units as well. For the air cleaner element, Citroën specifies Miofiltre, Lautrette and Quillery but only using its part number instead of some manufacturer code.
The advice is plain and simple: never use them! There are many oil additives and so called engine treatments (often sarcastically referred to as snake oils) available on the market but they all share one thing in common: none of them was ever proven to be advantageous, actual tests found quite the contrary more than once. Manufacturers routinely claim that independent laboratories tested their products scientifically but they don't rush to disclose the names of those laboratories or the circumstances under which the tests were conducted.
The primary job of the oil you put into your engine is to stop the various metal surfaces from grinding together, causing rapid wear of the parts. At the same time it has to dissipate the heat generated from friction, to transfer part of the heat of combustion away, to hold the byproducts of the combustion in suspension, not allowing them to stick to the engine parts. The oil has to comply with all these requirements under significant pressure and a wide range of temperatures ranging from the chilled engine in a winter morning to the high temperatures in an operating engine.
All gasoline engines are four-cylinder, aluminum alloy, in-line, overhead camshaft, water cooled engines mounted transversely. The engine type can be found on the engine number and manufacturer's plates.
1124 ccm gasoline engines
A few models exported to Italy and Greece were fitted with engines normally used only in the AX.
The BX saw one major model change during its production life, the introduction of the Series II in 1986 (theoretically from July 1, 1986 or ORGA number 3522; but I know of Series II BXs from June, too). Although there are numerous differences between the older and newer models, two changes are very eloquent and help tell the two series apart without trouble:
The BX was introduced in 1982 as the successor of the GS/GSA series and was replaced in 1994 by the Xantia. The second most popular Citroën after the 2CV—with a total production of 2,315,739 cars—presents Citroën's distinct character in a package somewhat more conventional than the previous Citroëns.