I have an in-depth VERY detailed Heat Efficiency Calculator for ALL fuels.
I obtained this from the Internet this past year but I don't remember exactly where.
I have never used it but someday I will study it more because at first glance it looks intimidating.
It is a MS Excel Spreadsheet with a file extension of .xls which they do not allow to be uploaded on this site. If interested in obtaining the Excel file, send me a PM with your email address for delivery.
Dr4Film ----- Richard