Engine oil level is one of the few things any driver can check on their own, without tools or experience. Yet most people do it rarely, or do it wrong. The result is the same: the engine runs with too little or too much oil, and both shorten its lifespan. Here's how to check it properly, what to do when you need to top up, and which mistakes to avoid so you don't cause damage instead of doing good.
How to properly check oil level on the dipstick
Do the check on a level surface. The engine should be off for at least 5 to 10 minutes so the oil drains back into the sump, otherwise you'll get a false low reading. Pull out the dipstick, wipe it clean with a cloth, push it back all the way in, and pull it out again. Only that second reading is accurate.
There are two marks on the dipstick, MIN and MAX. The oil should sit between those two marks, ideally closer to the upper one. If the level is below the MIN mark, the engine is already running in a risk zone and topping up is urgent. If it's between MIN and MAX but near the bottom, topping up isn't urgent, but don't put it off for more than a week or two.
A note for owners of newer cars: some models no longer have a physical dipstick. Instead, an electronic sensor measures the level and displays it on the dashboard. The check procedure in that case depends on the manufacturer, but the principle stays the same: check regularly, don't wait for the warning light to come on.
How much oil to add and when it's actually needed
The distance from MIN to MAX on the dipstick in most engines corresponds to roughly 0.5 to 1 litre of oil. That's less than many people think. So the most common mistake when topping up is pouring in half a litre or more at once and overshooting the MAX mark.
Proper topping up looks like this: pour in about 200 to 300 millilitres, wait a minute for the oil to drain into the sump, then check with the dipstick again. Repeat as needed. It's better to add a small amount three times than too much at once.
Topping up is a normal part of maintenance. Every engine consumes a certain amount of oil, even when it's completely healthy. Manufacturers typically state that consumption up to half a litre per 1,000 kilometres is within normal range, though in most healthy engines the figure is noticeably lower.
Which oil to use for topping up
The basic rule is simple: use the same oil that's already in the engine, same specification and same viscosity. If you don't know which oil was used at the last service, check the service booklet or look at the label on the oil filler cap, where the manufacturer often lists the recommended specification.
Mixing different brands of the same standard is acceptable. If you have 5W-30 oil with the same VW or MB specification, you can top up with another manufacturer's 5W-30 of the same spec. What's not recommended is mixing different viscosities (for example 5W-30 with 5W-40) or mixing synthetic oil with mineral oil. Such a mix won't instantly destroy the engine, but it can compromise lubrication properties. If you're unsure which oil you need, check out our guide to choosing engine oil where we explained the differences between specifications and viscosities in detail.
Mistakes that damage the engine
The first and most dangerous mistake is ignoring a low oil level. When the oil drops below the minimum, the engine loses lubrication at critical points. Crankshaft bearings, pistons, and the camshaft run metal on metal, and at that point it's only a matter of time before serious damage occurs.
The second mistake is overfilling, and many people don't take it seriously. When the level goes above the MAX mark, the crankshaft starts hitting the oil and creates foam. Foamy oil loses its ability to lubricate, and the excess can travel through the crankcase ventilation into the intake manifold, damage the catalytic converter or seals. In short, too much oil is just as much of a problem as too little.
The third mistake is pouring in oil of the wrong specification. An engine designed for low-viscosity synthetic oil (say 0W-20) won't work well with thick mineral oil 15W-40. Modern engines have tighter tolerances and require oil with precisely defined properties.
When topping up becomes a sign of a bigger problem
If you top up once between two services, that's perfectly normal. However, if you notice the engine needs a top-up more often than every 3,000 to 5,000 kilometres, or if you're adding more than a litre per 1,000 kilometres, that's no longer typical consumption.
The reasons can be worn piston rings, worn valve stem seals, a leak at the valve cover gasket or at the oil pan. Sometimes oil leaks at the filter connection or the drain plug, which is a simple fix, but sometimes the cause runs deeper. If you notice blue smoke from the exhaust or oil traces under the car, don't delay getting it checked. Read more about what's considered normal consumption and when to take action in our guide on engine oil consumption.
Likewise, if your oil pressure warning light comes on, don't keep driving until you've determined the cause. Low oil pressure is a more serious issue than low oil level and can mean the oil pump isn't working as it should.
A regular oil level check takes two minutes and costs nothing, yet it can prevent a repair that costs hundreds. If you're not sure whether your engine is consuming more than it should, or you don't know which oil to use, stop by the shop. It's better to check now than to risk an expensive breakdown.