I am glad I found this post. I am sorry to hear of your bad MPG jjc!!!
Our 2001 Sequoia gets 15mpg all day and 18+ on the hiway. We have been wanting to trade in our Sequoia on a 06 Sienna just for the savings in gas. I still like the Sienna but I can not believe the difference in estimated and actual MPG. I just looked at
Fuel Economy and 6 people across the us got an average of 18MPG. That stinks in my opinion.
Weight shouldn't even be an issue. We owned 2 1993 VW Eurovans, one a weekender with pop top camper and they both got 18/22MPG (city/hiway) Talk about overweight and under powered 2.5 liter engine.
Good luck with your Sienna! I might just stick with our V8 Sequoia or even buy another VW Eurovan. (Yeah I know they need some fixin.)