Buy 20W-50 Engine Oil

20W-50 is the oil of the classics: engines with wide bearing clearances, no particulate filter, no longlife interval - and a design built around a thick oil film. On anything from the nineties onwards it is almost always the wrong choice.

Why old engines like thick oil

An engine from the sixties or seventies has wider manufacturing tolerances and larger bearing clearances than a current one. The oil film has to fill those gaps, and a thin modern oil does not: it runs off, the pressure drops, consumption rises. That is exactly what 20W-50 is made for.

Then there is the sealing technology. Classics often have felt and cork gaskets, older-style shaft seals and no crankcase ventilation by today's standards. A thicker oil stays where it belongs.

Typical vehicles:

  • classics and modern classics with carburettors or early fuel injection
  • air-cooled engines that reach high oil temperatures in use
  • very high-mileage engines where oil consumption on a thin oil becomes unacceptable
  • historic motorcycles and stationary engines where the manufacturer specifies it

Cold starts and the seasons

20W means this oil is stiff in frost. Below roughly -10 °C, starting puts the starter motor, the battery and the bearings under strain, because oil pressure builds too late. In practice 20W-50 is therefore a summer and shoulder-season oil for cars that are laid up over winter anyway - which is true of most classics.

If you use your car all year round, check whether the manufacturer names a thinner grade for winter, or consider a 10W-40, provided the engine's clearances allow it.

Mineral or semi-synthetic

Mineral and semi-synthetic oils are the rule in this grade, and that is not backwardness but intent: fully synthetic oils with modern additive packages are not always the better choice for a classic. Two points are rightly debated in classic-car circles - the level of zinc and phosphorus compounds (ZDDP), which older camshafts and tappets depend on, and compatibility with old sealing materials.

If there is a specialist or an owners' club with a clear oil recommendation for your car, follow it: with historic engines, documented experience carries more weight than any general grade specification.

A new oil filter belongs with the change, assuming the engine has one at all: some pre-war and early post-war engines have only a gauze strainer instead of a filter, which is cleaned rather than replaced.

Frequently asked questions

Is 20W-50 suitable for my 2005 car?

Very probably not. Engines of that era are designed for 5W-30 or 5W-40, often with a longlife requirement and a particulate filter. 20W-50 is too stiff there and carries too much ash into the exhaust. The owner's manual is what counts.

Does 20W-50 help against oil consumption?

On an old engine with wide clearances, often yes - that is the actual purpose of the grade. On a modern engine it treats a symptom and creates new problems, because hydraulic components and the oil pump are designed for thinner oil.

Can I run 20W-50 in winter?

Possible, but not advisable: below roughly -10 °C oil pressure takes too long to build, and the cold start stresses the engine more than a whole summer of driving. For a car used all year round, ask for an approved thinner grade.

Why do classic owners talk about ZDDP?

Zinc and phosphorus compounds form a protective layer on heavily loaded sliding surfaces such as the camshaft and tappets. Modern passenger car oils contain less of them, because these substances load the catalytic converter - a point that falls away on a car without one, but still matters to its camshaft.