Practically Classics Forum

Most old vehicles do not need fuel additives to be added to modern petrol, as the work surfaces had work hardened aftera great many miles...if the tappet clearances are not closing up you do not need a additive at all.........if the engine pinks on modern fuel just retard the timing slightly ..
My 1979 Escort mk2 has been using the fuel for as long as i can remember ...tappets still okay...and on removing the head the valves and seats are in fine order, so save your money...............
Jim..............

There's me reading the title and thinking of the palms of my hands....

This is a common misconception.
Granted; some iron-headed engines can last on unleaded fuel if driven gently and not thrashed or laboured, but the valve seat areas cannot possibly have work hardened since they would, in any car made before inserts became common, have been isolated from contact by that layer of lead.

Okay but my Escort has covered all together 160,000 miles .......half of that on unleaded fuel, no pitting on inserts or valves and the lead will have worn off ages ago........tappets have not closed up as one would expect if there was a problem, we certainly do not drive with a light foot either.
These old cars are such fun to use, always change oil/filter every 5.000 miles.......decent oil of course.
Jim.............

A work hardened surface can only be as good as the type of material used and even then its wont just keep getting harder,something sooner or later will wear.
Also work hardening will only harden a thin layer on the surface its not like a fully hardened insert.