Wifi automatically disables mobile data. Wifi has highest priority. But turn it off if you aren't connected to wifi, because then it wastes battery searching for wifi
Yes you are partly correct, but not entirely. The active data service is indicated by the blue symbol, immediately letting you know whether the 4G, 3G, or WiFi is pulling data. The problem is, even when WiFi is blue and 3G/4G is grey, the 4G will continue to search for and maintain the data signal. You can tell pretty simply by the way that the device will jump between 3G and 4G sometimes, even when WiFi is the active connection.
With that being said, actually physically turning off data will disable the data search function, ultimately saving battery. The same can be said about WiFi. Even when WiFi is in a grey state, the fact that it is on means that it is refreshing the available servers every 60 to 90 seconds (depends on device). So when you leave the house, or anywhere else that you might connect to WiFi, be sure to disable it!
Instead of dealing with Smart Actions, which I don't particularly like running constantly, I prefer to use a toggle widget called "Extended Controls". It is just like the toggle widget that comes with the phone, but with way more custom options. I use the extended control widget on my home screen to manage screen brightness, volume, silent on/off, WiFi, Bluetooth, GPS, all very quickly and easily. I prefer to have manual, immediate control over these functions at all times, because Smart actions can't possible cover the constantly changing needs I might have.
Hope this helps, and btw, Extended Controls is worth every penny!
![Cool :cool: :cool:](/styles/smilies/google/cool.png)