I just looked at Chris's webpage showing the differences, notably that 10 new briquettes weigh 1/4 oz less than 10 old ones. What jumped out at me was the side by side picture showing the new product as slightly thicker. I think that picture says it all. It shows the grooves are pretty deep, nearly to the to the midpoint. Looks to me like just the right amount of charcoal missing to lose the 1/4 oz per 10 briqettes. And as others have mentioned, there is no way less product can burn both longer and hotter without higher energy density (chemicals). Even the same amount of charcoal can't do BOTH without this sort of tinkering, let alone less charcoal. I guess they could use different types of wood to achieve this, but I doubt it. I always thought the big charcoal makers basically used just odd scraps anyway?
That picture also proves that they WILL burn hotter (all else being equal) because there is more surface area to burn at once. How much hotter is the question. Also just a hunch, but looks to me like they would fall apart quicker. This would create even more surface area and could cause mini-temp spikes and the charcoal to burn up even quicker (assuming there was plenty of oxygen, which is most likely). That could explain some of the problems people have mentioned.
This leaves the burn longer part of the equation. Again, echoing others, that is not Kingsford lying. It is Kingsford "marketing"
. I think Kingsford's own response to this very question says it all. Rather than say, yes the briquettes do indeed burn longer, they say "Please take note they are ready to cook on sooner..." -so if you can start grilling fifteen minutes sooner, but the charcoal burns out ten minutes faster, you still "gained" 5 minutes of "usable" burn time right?
Sorry for the long post. I know I'm a newbie at this forum, but I just thought I'd share my thoughts. I use Kinsgford when not using lump, so this topic really burns me
BTW- I've been a "lurker" at this site for a couple years.