INSTANT EXPERT
Grease remains an essential motorcar lubricant. Yet, even professionals misunderstand it, leading Rob Marshall to redress the balance.
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One of the marvels of modern motorcars is the fewer maintenance operations. While routine greasing tasks have not been eradicated, at least DIYers do not have to face a plethora of greasing jobs every 3000-6000 miles. Even so, modern motorcars utilise grease, not all of which is the same.
According to Adrian ‘Ade’ Hill, Technical Manager of Morris Lubricants in Shrewsbury, our technical partner for this feature:
“The most common misconception among DIYs and the motor trade is that multipurpose grease can be used for everything.”
This feature, therefore, investigates issues that tend to be overlooked. These include grease composition, how it works, why it fails, what different types are available and how a DIYer should use it to ensure maximum component life.
Back to basics
Even on electric vehicles, modern motorcars have multiple lubrication needs. Many of these are selected carefully by manufacturers and their suppliers. In areas, where liquid oil will leak out, grease is employed, instead.
By suspending the oil in a thicker substance, a component can still be lubricated, without the oil escaping. Apart from acting as a lubrication reservoir, grease reduces component noise and vibration. It also can hold solid particles in suspension and its strong molecular chain prevents it from breaking down under high loads. Its adhesive nature is also useful, especially in situations where water washout can occur, such as these encountered in off-road driving conditions.
Grease also provides a barrier against solid and liquid contaminations from entering the component, such as abrasive grit, or corrosive moisture. Dependent on the application, manufacturers can blend anti-corrosion additives with the oil to add extra protection. Surprisingly, some greases can absorb and hold a degree of water contamination in suspension to prevent it from affecting the component’s working surfaces.
Interestingly 70% of all bearing failures are due to contamination. The causes tend to be mechanical seal failure, causing the grease to be overwhelmed. By the time the owner has discovered the failed seal, the bearing is likely to have worn excessively, due to lack of lubrication. If caught in time, re-greasing the bearing and replacing the oil seal will extend its life.
Yet, grease is not perfect. It has poor cooling properties, tolerating neither excessive temperatures, nor significant fluctuations. As grease releases its oil content when squeezed, it has to be compressible. Therefore, it is unsuitable for applications, in
