Leaded and unleaded

mocha ( snipped-for-privacy@host.com) gurgled happily, sounding much like they were saying :

Surprisingly, the difference is "Lead". Or, to be specific, tetraethyl lead.

If you have some leaded, you'll either have paid a helluva lot for it because you actively want it

Well, possibly irrelevant as well, as you can only buy leaded for specialist classic cars now.

Simply put:

Leaded uses, er, lead to add anti-knock properties to fuel, it also lubricates and cools the valves.

Unleaded uses substitute chemicals to achieve the anti-knock properties (such as benzine), but does not have the lubricating and cooling properties of leaded fuel.

Cars made after 1988 can all run on unleaded, they have specially hardened valve seats to cope with the reduced cooling and lubrication.

Cars made after Jan 2002 have catalysts fitted and can *only* uses unleaded. Lead damages the cat, although it can take a while and a small amount is not harmful.

Yes, indeed on some older cars that had the un-hardened valve seats, you could often mix the two at a ratio of 3/1 unleaded to leaded, and still prevent damage to the valves.

The clue is in the question.

Yes, well, maybe, depends on the car.

HTH.

Apart from what has already been said, the practical difference between the two, is that the lead gives a wear resistant surface to the valve seats. Important for those engines with valve seats machined directly into the cast cyl head. Without the lead, valve recession usually occurs on such engines. This is where the valves wear the seats, forming a 'pocket' as the valve sinks below the original surface. To make such heads suitable for unleaded fuel means machining, and fitting hardened steel valve inserts.

Yes. The ratio might determine whether it's suitable for a 'leaded' or 'unleaded' head. If the car has a cat, the answer would be no, or should I say, inadvisable if you valued the cat. :-) Mike.

But since January 2000, leaded petrol is no longer sold at stations.

Oh yes it is!

Oh no it is!

Hmm. I must admit that I didn't know that.

No it isn't. Lead Replacement petrol is, nut not leaded.

Oh, read the link before you make a tit of yourself AGAIN, Conor. Leaded petrol you *can* buy - now you find me a list of stations still selling LRP. Go on, I dare you...

There is a small chain of petrol stations called "THRUST" that still sells

Not near enough for Conor, it would seem.

But more than enough for Mr Leadbitter, I should think.

The message from Conor contains these words:

Nope, you can still get real 4* with real lead in it. Exception was made for, IIRC 1% of sales volume to be the hard stuff. The website up there ^ somewhere even has a spec-sheet...

Surely 1992....:-)

I can buy it at my local and do so as it's much less likely to block my camping stove up......

But it's not LRP petrol Conor - do try and read it! There's even places in East Yorks that are selling geniune 99 RON tetraethyl leaded fuel if you look hard.

Thrust Swillington on the Wakefield/Garforth road as well sell it.

Feckit, yes.

Out of interest, how do Bayford make it? Just buy 95 premium wholesale and add tetraethyl lead (IV), which boosts the octane? Or do they refine their own stuff?