Lead Substitute - Necessary?

[Bolek]

Do you guys run lead substitute in your cars?

I have an 86 and wondering if running it is necessary or not.  I always hear stories of valves being damaged but unsure if that's a risk at all on these cars...

[ChrisRLewis]

If it's an aircooled model I would use an additive just to be on the safe side, it's cheap enough and will do no harm.

[Rusty's Uncle]

This subject has been a massive debate over the years and I have my theories on it. The idea of lead or other additives in petrol are partly to protect the valve seats & not the valves. The two worst burnt out valves i have ever seen came from a 500 and a126 engine but the seats were fine. I put that down to valve faults or poor seating & in either case the engine will be exploding fire and gas through the leak at 2,000 times a minute or so when driving. I an not sure when lead was first put in petrol but I think that the original 500 engines would have been designed to run on unleaded spirit. There are guys who say they have driven cars hard for over 100,000 Kms with no problem. All of the cars have hardened seats set into the aluminium heads and whilst I can't imagine that they downgraded the material quality on the 126 the owners handbook does say to run leaded fuel every 4th tank or so. After looking inside many air cooled engines I have yet to see one with damaged valve seats. It is an easy job to check out the tappets or valve clearance on the two exhaust valves if you have any worries.

[124cso]

......... I an not sure when lead was first put in petrol but I think that the original 500 engines would have been designed to run on unleaded spirit. ,......

Tetraethyl lead was first put in petrol /gasoline in the 1920s. It's main feature was to increase the octane rating of the crap fuel as cars increased compression, thus reducing engine knock or pinking. The lead coating of valves and seats was a helpful bi-product and helped reduce the build up of heat which was obviously transferred from one to the other. It also helped valve seats in vintage cars (valves lapped straight into the cast iron) that had previously needed valve grinds, perhaps every couple of months ?
The 500s and 126s have alloy heads so naturally have hardened insert seats, so should not need lead although they are only air cooled and this may have a risk factor ? but so do VWs and millions of motorbikes and industrial engines !
Then there IS that statement in the hand book - insurance on the part of Fiat ? You cannot buy leaded fuel in this country (30+ yrs now), other than Avgas or racing fuel, so I add 'Chiron VP Plus' and I THINK it SOUNDS quieter running ?

[amam]

so what do people do, just put some lead replacement in every so often?

Been alloy with inserts for the valves i thought it would be completely safe to run on standard unleaded (but obviously a higher octane fuel and not this rubbish supermarket stuff)