The formulations required for modern vehicles are very different from those needed for older vehicles. Oils for modern engines comply with the latest API ratings of SG and SH and are ideal for the design of a modern engine.

A classic car engine has the opposite characteristics with cork/graphite/rope seals, low pressure cog driven oil pumps, wider oil ways with greater dependence on "splash" and "cling" lubrication, lower revving with lesser machine tolerances.

Such a widely different specification demands a totally different lubricant.