QIRECENTLY bought an XF Falcon and was told by the owner and his parents that the car ran on unleaded. When I got the car home and looked under the bonnet I noticed the build date was July, 1985. I had someone have a look at the car and they said the fuel spout behind the number plate is too big and that they were usually on the leaded Falcons, but my dad says it might be unleaded because of the alloy head. Nathan Douglas,
ATHEshort answer is there is no simple way of checking. Preunleaded cars had a larger fuel filler, and to avoid owners accidentally filling their cars with leaded a smaller fuel filler neck was used on unleaded cars, which mated with the smaller nozzle at the servo. Though the alloy head had a valve-seat insert, it might not be sufficiently hardened to cop the pounding from unleaded fuel. I also doubt Ford would have changed the valves to the hardened ones needed for unleaded fuel. All this suggests you shouldn’t run the car on unleaded without an additive.