what octane fuel did 1980 rover SD1 2.5 engine require, leaded or unleaded?
SD1 V8 1980 in MGB 500 cfm carb
Your car needed unleaded as your car should have a catalytic converter at least in America. HOWEVER! Your car has had an engine swap and I have no idea what emissions it has. It may not have a catalytic converter. BTW The 2.5 is not a V8, the 3.5 is. The 2.5 is a 6. In the US the Rover V8 did have cats when new. Are you sure about what engine you have? I suggest you have a British car mechanic help you sort out your car.