Did another test run with the 52 inch curved light bar.
It causes at least a 10% range loss at 55mph.
It could be up to a 20% range loss at 65mph.
Definitely don't permanently attach one to the roof of your car if you need most of your cars range and drive on the highway.
"THE ABOVE POST CONTAINS MISLEADING AND INACCURATE INFORMATION. PLEASE CONSIDER IT OPINION, NOT FACT". -someone who I offended and is unable to produce the facts in question.