I attempted a quick fuel cut on 2 of 4 cyl on my corolla one day, ran fine, vibrated quite a lot, could have been driveable but desided to clear the check engine light and drive home. My big 105hp engine cut in half + other losses would probably make a turd but maybe great mpg.
I would like to see more attempts on a cyl delete. The cars I drive directly push on the valves, so only way to "delete" them would be to grind off the lobe on the cams.
I suspect a 1 cyl delete would run pretty off, but shouldn't be super bad, depending on how the engine is designed, and what the ECU does because of the delete. I would say not one answer covers all cars.
On a side note, I do have an extra set of cams for my Camry from an engine that ran out of oil, could be interesting, but too old for instant MPG feed back
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