Man checking oil

Rights and wrongs of checking fluid levels

Oil and water might not mix, but your car’s engine needs both to keep running. Let either of these vital fluids run low and you’ll be heading towards engine damage or, worse, catastrophic failure.

By Shell on Sep. 14, 2020

For this reason, checks of your oil and ‘water’ – we say ‘water’ because it has been replaced as an engine-cooling medium by purpose-made liquids called ‘coolants’ – should be a mandatory part of your periodic car-maintenance checklist. Here’s how to do it right.

Engine Oil

First, park your car on level ground. If the engine’s been running, wait about five minutes to ensure the oil settles in the sump and is level. If you haven’t used your car, start the engine to get oil pressure and allow oil to fill the filter. Both methods will help you get a more accurate reading.

Next, locate the engine-oil dipstick – your owner’s manual will tell you where it is – pull it out and clean it with a lint-free rag. (A dirty cloth or newspaper may introduce nasty contaminants.) Then reinsert it and pull it out again, and see if the oil level falls within the minimum and maximum markers.

If it’s closer to minimum, you’ll need to purchase the correct grade of oil and top up via the engine-oil filler – your owner’s handbook will offer guidance for both, but the latter is typically on top of the engine.

Always add oil in small amounts to avoid overfilling, periodically checking via the dipstick. A funnel will help immeasurably.

Engine coolant

The big rule for any cooling-system check is to make sure the engine is completely cold, because the system not only reaches incredibly high temperatures, it is also pressurised. Opening it up while hot can result in an explosion of boiling water and steam.

Checking your coolant level is as simple as locating the coolant-overflow reservoir – again, look in your owner’s manual – and seeing if the level sits between the minimum and maximum marks. As with oil checks, you want to be parked on level ground for an accurate reading. To top up, unscrew the coolant-reservoir cap, then carefully fill to the maximum marker.

If your car doesn’t have a coolant reservoir (many older ones don’t), open the radiator cap and look inside the filler neck. If you can’t see coolant, top it up until the coolant reaches the bottom of the neck. Make sure the radiator cap is properly retightened.

Different cars require different types of coolant, so check your owner’s manual before purchasing. Never top-up with tap water – it can cause corrosion inside your engine and lacks the anti-boil and anti-freeze components to stop it overheating, or freezing up in sub-zero temperatures.


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