Ask an expert

When should you check the engine oil level - when the engine is cold or warmed up?

The reason I ask is that after a recent service I checked the oil level next morning to find that it was about a centimetre over the top level on the dipstick.

When I went back to the garage the mechanic told me that I shouldn't check the oil level with the engine cold.

He then checked the level (engine warmed up) and found it slightly over full mark but thought not enough to worry about.

William

From the "Ask Jack" archives - 14 September 2009

In theory, on a average 4 or 6 cylinder engine there may be slight differences between hot and cold engines but not a centimetre of discrepancy.

I suspect the mechanic has simply added too much oil, end of story.

Most modern petrol engines have less capacity than they use to, so a centimetre over full could equate to around half a litre too much oil has been added.

Let the engine sit for say 10 minutes after returning home one day and recheck. Less than a centimetre overfull I would not worry about, but if you take the car back to the same place in future, ask them to be a bit more careful and let them know you do not want to pay for excessive and unnecessary amounts of oil.