Yeah that'd be about right I reckon. Add the extra weight and IMO that final ratio difference, mine being a 5spd.
The TF Advance I had, would gladly sit on anything between 7.88-8.5ltrs hwy avg. The TH Manual sports about 8.5-9ltr but had some work done.the TH solara about 8.5-9.0 and the GTV as I stated about 9+ltrs