If you're not deactivating at least the intake valve, you're not going to see much of an increase in fuel economy.
This website has a number of factual mistakes in it.
First of all, traditional cylinder deactivation schemes do contribute to overall engine efficiency in that the firing cylinders in a variable displacement engine have higher peak compression pressures than with a similar engine with no variable displacement scheme in place. This is in contrast to this item:
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Second, pumping losses are less with a traditional cylinder deactivation scheme than with this DCD gimmick because the deactivated cylinders do not pump air. Therefore, they do not contribute to forming economy-robbing engine vacuum, nor do they contribute to economy-robbing exhaust flow.
Third, since there is no airflow through the deactivated cylinders in a traditional cylinder deactivation scheme, the deactivated cylinders will approach average coolant temperature. This is in contrast to this DCD gimmick, where airflow through deactivated cylinders may actually cool the cylinders below average coolant temperature. This is the so-called "thermodynamic expansion" mentioned with DCD.
I'll leave it up to Mr. DCD there to explain how his electronic gadget is going to fool the engine computer from sensing the extra oxygen in the exhaust stream from his DCD algorithm, and fooling the engine computer from applying extra fuel to compensate for that sensed extra oxygen.
You'd be better off checking for correct tire pressure, than with experiementing with cylinder deactivation schemes that do not shut off airflow to the deactivated cylinders.