I'm no mechanic but I think I worked out your fuel consumption problem.
If you look at these all linked together it makes sense.

1. Driving in first gear (not unusual)
2. Driving in first gear at 100km/h (slightly unusual)
3. Driving in first gear at 100km/h with the handbrake on. (unusual)
4. Driving in first gear at 100km/h with the handbrake on will cause mild to heavy fuel consumption. (very unusual)
If you need me to troubleshoot any more issues please let me know I'm here all week.
