Tuesday 10 January 2012

The Bodger's Guide to Oil

Oil is the lifeblood of your vehicle. It lubricates, it cools and it provides hydraulic pressure. Or at least it should.

We all know that oil fails us every now and again. Sure, the "professional" mechanics will blame bearing wear or faulty parts from eBay or all those third-gear burnouts. But somewhere, lurking in the back of the mind, is the idea that maybe the oil has let us down. This gives rise to another phenomenon - the grasping, desperate hope that oil can fix the problem.

Let's examine the details.

Mechanics and oil companies will tell you there's a multitude of oil grades, differentiated by SAE numbers like 20W50.

This is a lie. There are only two grades of oil - too thick and too thin.

Oil that is too thick will make the top end rattle when the engine is cold, as the goop doesn't thin out enough to get to the cam and rocker gear. There's two bits of good news though - the bottom end, close to the oil pump, has plenty of pressure, and the wear that the unlubricated top end is experiencing will soon mean you need the thick oil anyway.

Oil that's too thin is worse - like middle management, oil is the cushion between big stationary objects and things that would otherwise pound against them. When the cushion gets too skinny or has a long lunch at the pub, carnage can result.

Fortunately, oil that is too thin can be easily replaced with oil that is too thick.

Here ends the lesson. Next week, we'll take a look at nuts and bolts.

A note on the disposal of oil: Recycling is important in this environmentally conscious age. This correspondent has successfully drained oil out of a Kingswood, used it for 5000k's in a Falcon, then used it for years in a mower. I wouldn't recommend recycling any more extreme than this.


  1. I thoroughly approve of the oil recycling method. I used to use oil for 3-5000km in the good car then put it in the crap car for about 5000km then dispose of it.

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