In the view of bus operators, Gradner engines have a very significant advantage - they are remarkably more fuel efficient than competing products. I
remember reading articles in magazines quoting a Gradner-engined Olympian can manage a fuel consumption figure of 9mpg (mile per gallon), in contrast
to Cummins' 5-6mpg. I think Hong Kong operators' transaction to other products is more a Gradner failure to produce new engines.