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The comparison is done by "Advanta Star" a research company, clearly visible on the page where you set up the comparison (also in the fine print at the end of the article), and not by Toyota.
If you want information from Toyota, visit their official web site at http://www.toyota.com .
Second I would imagine that this service will be here for the 2003 model. Now when Toyota compares the V6 model to a model with a cast iron block, it will probably say the V6 engine is lighter and has a better heat distribution than that of a cast iron block.
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)