Buy 5W-50 engine oil

What the wide range is good for

An oil spanning 5W to 50 has to work across a large range, and that calls for high-quality synthetic base oils with a shear-stable viscosity package. The benefit lies where oil temperatures are permanently high: turbocharged sports engines, vehicles towing in summer, high-mileage engines that use a measurable amount of oil on a 40 grade.

Against 5W-40: more reserve in the heat, a little more internal friction. Against 10W-60: a better cold start, less extreme high-temperature viscosity - for an everyday vehicle usually the more sensible of the two.

Approvals

ACEA A3/B4 is the usual one, plus brand-specific numbers for high-performance engines. The important point is the same as with any thick oil: most 5W-50 oils are **not** Low SAPS and therefore do not belong in a vehicle with a diesel particulate filter or a petrol particulate filter unless a C approval is explicitly on the container. For vehicles with a filter, the way leads through ACEA C3.

And as always: moving up a grade on your own initiative because "thicker protects more" is not a good idea. Hydraulic components such as chain tensioners and camshaft adjusters are designed around the intended viscosity.

When the engine uses oil

Engines for which 5W-50 is intended often use some oil by design. Carry a bottle of the same product and check the level before longer or faster journeys - at high oil temperature, too low a level is the more critical of the two errors.