Unleaded Petrol

[sigma]

Going back to the days when unleaded petrol was first introduced, why couldn't certain cars run on unleaded.

[murraymints]

something to do with the catalytic convertor ?? guess..where's Tony ? he'll tell you all the details

[bhg481]

The lead in the petrol acts as a lubricant for certain parts of the engine (valves, I think).

[EDDIE51]

^ Yes the valves needed the Lead to lubricate them.

[Noe-schitt]

Exhaust valves in particular. New harder valve seats have to be fitted to run on unleaded

[razza]

Yes it was all to do with valve seating,required hardening for unleaded,expensive to convert but most people put an additive in to compensate for lack of lead,luckily at the time I had a 1985 Granada and it was able to run on either

[DTCwordfan]

yes the valve seats were soft and needed lubricity afforded by the lead solution in the fuel.....

when the conversion over came, there were issues with some of the additives with false claims that tin-based solutions could compensate.

[DTCwordfan]

lead solution additives were mostly fine.......

[MantaRay]

Earlier car engines needed lead in the petrol to help protect the cylinder head valves and seats from erosion and/or pitting. However, when catalysts came along to help clean up exhaust gases the lead had to be removed in order to protect the catalyst matrix. The lead would render the catalyst useless fairly quickly.