Running low on oil is one of the fastest ways to destroy an engine, and it is completely avoidable. Checking your oil takes two minutes and needs no tools.
How often to check
Once a month is a good habit, and always before a long trip. If your car is older or you know it uses a little oil between services, check every couple of weeks.
Do it properly
Park on level ground and check with the engine cold, or at least 10 minutes after switching off so the oil has drained back down. Checking on a slope or straight after driving gives you a false reading.
Reading the dipstick
Pull the dipstick out, wipe it clean with a rag or paper towel, push it all the way back in, then pull it out again and look. There are two marks — a minimum and a maximum. You want the oil film sitting between them, ideally closer to the top mark.
Some newer cars have no dipstick at all and show the oil level on the dashboard screen instead. Your manual will explain how to bring it up.
Topping up
Use the exact grade listed in your owner's manual — something like 5W-30 or 0W-20. This is not a place to guess or use whatever is on the shelf; modern engines are built around a specific oil thickness.
Add a small amount at a time, wait a minute, then re-check. Going from minimum to maximum usually takes around one litre, but add it in stages rather than all at once.
Do not overfill
Too much oil is as bad as too little. It can foam, build pressure and damage seals. If you go over the maximum mark, have it drained back down.
What the colour tells you
Fresh oil is light amber. It darkens with normal use, so dark oil alone is not an emergency. What is a problem: a milky, creamy look (possible coolant mixing in) or a gritty feel between your fingers. Either one means book a mechanic.
If you are topping up often, that is a message. A car that drinks oil needs to be looked at, not just refilled.