“There are, however, engines which simply cannot run on unleaded fuel. These are mostly older designs, with inlet and exhaust valves directed on a cast-iron cylinder head – and the lead is needed to lubricate the valves and valve-seats. Without it, they would deteriorate through corrosion and burning. To a lesser extent, very high-compression, highly tuned engines can’t be easily weaned of leaded fuel, either.
“In addition, there are power units that need modification in order to run on unleaded. A franchised dealer will tell you whether your car can be converted economically – or refer to the relevant Department of Transport booklet or a chart produced by CLEAR (the Campaign for Lead-Free Air).
“All that needs to be done is for the ignition timing to be retarded by a few degrees, thus causing combustion to occur fractionally earlier. Most dealers will charge £10-£20. On the other hand, dealers of prestige makes might charge up to £80 for turning an ignition chip around.
“Catalyst power units, though, are a different matter; these cannot accept leaded fuel under any circumstances, and damage will result unless unleaded is used."
So, how easy would the switchover be?
Autocar explained: “After what must be regarded as a period of complacency, a lot of Rover Group cars cannot take unleaded – among them all Metros bar the 1.3GS, about half the Montego range, and all Maestros and Rover 216s. However, current valve-seat development will ensure that all models built after this spring will be able to accept it, with the exception of the MG Metro Turbo and Maestro Turbo.
“Virtually all existing Fords can run on unleaded but, apart from the new 1.8-litre Sierra, they will need to be adjusted. Just the Escort RS Turbo will require leaded.
“The V12 cars will soon be factory-set for unleaded; fortunately for Land Rover, the Range Rover’s all-aluminium V8 needs no re-engineering before it can be retimed for unleaded.”
Catalytic converters are universal now, but they were almost unknown to the British public in 1989.
“Contrary to widely held opinion, an engine tuned to run on unleaded fuel and an engine with a catalyst are not the same. Have your car retuned to use unleaded, and it won’t pump lead into the atmosphere, but it will continue to emit carbon monoxide, unburned petrol hydrocarbons and nitrogen oxides (NOx) – all poisonous. These gases produce smog and contribute significantly to the acid rain that is having such a dire effect on European forests. A catalyst engine, in contrast, produces an exhaust that’s free of these pollutants.