Engine Oil for Your Classic Car
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 SN/CF and specific ACEA and OEM specifications dealing with fuel efficiency, extended drain intervals and aftermarket exhaust treatment systems and are specifically designed for the modern engine needs.
A classic car engine however, can have the opposite characteristics with cork/graphite/rope seals, low pressure gear driven oil pumps, larger oil galleries with greater dependence on “splash” and “cling” lubrication, lower revving with larger machine clearances. Such a widely different engine design can demand totally different lubricants.
Inadequate detergent can result in gums and lacquers clinging to the hotter engine components, and blocking oil galleries – but, too much detergent can cause a build-up of metallic ash in the combustion chambers and piston crowns. In older engines with traditionally high oil consumption, this can cause detonation and pinking.
In older engines where the carbon has built up over a number of years, detergents can have a scouring effect, causing the carbon to flake off, blocking up oil galleries and spray jets. High levels of detergent can also “wash” traces of carbon from seals and gaskets, revealing oil leaks where the carbon itself is creating a seal.