Kingsford has once again changed their formula to increase the amount of charwood, making bags lighter for the same number of briquets. They did the same in 2010. They claim the same number of uses per bag.
I ran a side-by-side burn test last weekend and will publish the results soon. Spoiler: the old stuff lasted just a bit longer than the new stuff, but not by much.
I noticed last week when I did a test burn on my Brinkmann Smoke'n Pit Offset that the new Kingsford did burn hotter, but not as long as the older Kingford. With the old Kingsford, I could get stable temps (250*) and a 5 hour burn from one basket. With the new Kingsford, my pit burned hotter and I has to keep adjusting the input air vent and got only 4 hours burn time. I used the same amount of coals both times and the outside temp was about the same. I was wondering why, now I know. The new formula burns hotter, but has about 25% less burn time and produces less ash and smoke.
I've examined both 2014 and 2015 K and I don't see any difference in shape or size. Having said that, when comparing any two bags of charcoal there can always be variations in thickness of briquets due to variations in the stamping process. But what's new about the 2015 formula is something about "increased airflow". Not sure how that's achieved, as they're not providing details.I read that they changed the briquette shape or and or size as well to increase the surface area..
Thanks for spending the time to test the new KBB. I also read your article on your visit to the test facility back in 2005. Full of great info.