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BTW, I think Toyota had some in-line fours at least some years ago, with cylinder deactivation during idle, or perhaps even at light load. I've heard such a car cycling slowly between normal mode (all four cylinders) and a more rough sound of fewer cylinders firing while talking to the owner utside the car. (she didn't know anything about the engine though)
In the 1940's and 50's there were some bizzarre petrol engine conversions called Hesselman diesels, mainly in trucks and busses. The most common engine was a 6-cyl Volvo engine with low compression (even for a petrol engine, I think it was around 7:1). The engine had powerful spark-plugs for ignition and two slightly special valves per cylinder, giving an extra good swirl. Once started on petrol the Hesselman could switch over and run on the much cheaper oily diesel, -probably with a lot of black smoke and poor efficiency. To keep cylinder temperature up, the idle was kept quite high, and to help it even more, half of the cylinders were completely shut off to make the remaining three work a lot harder. (probably resulting in an extra dense black turd while driving off again...) There were a lot of problems with these engines due to soot and inlet valves that could not rotate the usual way.
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