No the Prius doesn't drop cylinders to increase MPG the way some cars do, I think the 1.8L hybrid engine is efficient enough that it would not help, and would probably decrease efficiency, anyway. I don't know if that information would be on the data bus for the ScanGauge to read if you had a car with that feature, such as the Honda Accord V6. Honda sites might know, maybe they have an Xgauge for it.
The correct term is cylinder deactivation. From the title and the first post, I thought the OP was talking about a cylinder that literally cut out and stopped firing. GM likes to use the buzzword "Active Fuel Management" for this technology, which is quite annoying as they usually use it when marketing monstrosity class SUVs.
Cutting out 1 or 2 cylinders on a 4 cylinder engine would make for a pretty raggedy feeling engine. It would also be a smaller benefit when you have an eCVT and the engine management system we do. The purpose of cutting cylinders out on a V8 is to move the remaining cylinders to a higher efficiency region on the BSFC map, something a Prius already does a very good job of with the eCVT and engine management.
That's for sure. I drove a 4-cylinder 3-speed automatic 1989 Ford Escort hatchback. Then it decided to become a 3-cylinder about 5 miles after getting a 65k service. It wasn't terrible as long as it had some throttle, but at or near idle it was pretty awful.
