Car Mechanics (UK) - - Engine Oil & Lubrication -

Mod­ern 20W-50 lu­bri­cants are un­likely to pos­sess the same com­po­si­tions as those blends of 30 or more years ago. Should you own a his­toric ve­hi­cle, you might have no­ticed that 20W-50 prices match those of mod­ern oils in some cases. One ex­pla­na­tion might be re­duced economies of scale, but con­sider also that dis­cern­ing clas­sic car own­ers are pre­pared to pay more for peace of mind. Nat­u­rally, re­tail­ers are happy to oblige...

While cer­tain oils take ad­van­tage of mod­ern tech­nol­ogy to im­prove their for­mu­la­tions for older ve­hi­cles, buy with care. Many clas­sic car oil blenders cite the im­por­tance of in­creased ZDDP (Zinc Dialkyl Dithio­phos­phate) lev­els, which were re­duced over the 1990s be­cause they dam­aged catal­y­sers. Ad­di­tion­ally, mod­ern en­gine de­sign en­hance­ments, such as rolling rock­ers re­plac­ing flat tap­pets, mean that they are less re­liant on ZDDP as an anti-wear ad­di­tive. Duck­hams ar­gues that ZDDP for older en­gines is ef­fec­tive only at cer­tain con­cen­tra­tions and ad­vises CM read­ers not to rely solely on clas­sic oil with the ‘most’ ZDDP, be­cause other fac­tors are just as rel­e­vant, such as a de­cent base oil qual­ity that en­sures the anti-wear ad­di­tives work ef­fec­tively.

For more main­stream ve­hi­cles, Adrian Hill, au­to­mo­tive prod­uct man­ager at Mor­ris Lu­bri­cants of Shrews­bury, re­ports that de­mand for 10W-40 (in both min­eral and semisyn­thetic) blends are in de­cline. If you own an older car that uses 10W-40 or 20W-50, the API/ACEA spec­i­fi­ca­tions will give you an idea of its per­for­mance lev­els, mean­ing that you can com­pare dif­fer­ent oils with the same vis­cos­ity.

Shell con­firms that 5W-30 has be­come the most pop­u­lar vis­cos­ity in north-west Europe. How­ever, all 5W-30s are not cre­ated equal and man­u­fac­tur­erspe­cific oils are con­sid­ered nor­mal. This has re­sulted in a huge range be­ing avail­able – Adrian says that up to a dozen 5W-30 oils were in Mor­ris’ range at one time but, un­sur­pris­ingly, oil tech does not stand still.

While many car man­u­fac­tur­ers rec­om­mend that you use a cer­tain brand, the spec­i­fi­ca­tion pro­vided is even more im­por­tant. Do your re­search care­fully.

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