re: I assumed they were talking burning efficiency, not overall thermal efficiency
"Otherwise the "BS Flag" would have instantly gone up. "
The burning efficiency of modern car engine is high, I think it's in high 90's and there isn't a lot room for improvement. There is lots of BS in article, but regardless of that [and perhaps it's mostly because reporter in clueless AND these guys are trying to hype their product] it's possible this could be useful product.