I was doing reading elsewhere, and I noticed an very interesting correlation... This ultra-fast drain has only happend twice before, and BOTH times, I was on a multi-hour trip on a bus! When I commute to/from work, the phone is on charge on the cradle in the car. Someone made a point that either GPS, or WiFI etc etc.. is searching and searching, and running the battery down. I see I have 'airplane mode' that turns the radio off, but then I wouldn't be able to send/receive calls. --I think there's a way to just turn off 'data', and leave T1xx up and running? (voice and SMS, but no IP / no apps)...?
GPS only "activates" when an app requests it to. My GPS is always "on", or more like, "ready if needed". The GPS icon will appear in the status bar when it's actually working.
For WiFi, since you're driving, there's no use for WiFi as you'll never be in range of any access point long enough. Turn it off. You could adjust how often it scans for WiFi access points (basically it wakes up the WiFi interface looking for connections and notifies you if it finds any). The default interval varies wildly ! Mine is set at 360 seconds (6 minutes). If I have to, I can *force* it to re-scan if I go someplace with WiFi.
See if your device has a "sleep" mode or "nighttime" mode. It's like a pseudo-airplane mode. It generally dims the screen brightness, turns off data (WiFi, 3G/4G), but leaves cell data on so you can receive calls and text.