How to check oil in a car or motorbike – and how often

how to check oil

Explains step-by-step how to check oil in a car or motorbike, how often you should check, the difference between a wet sump and a dry sump, and what to do if there is too little oil — or too much.

Car and motorbike owners should check the oil level every month. In modern cars, digital checks are also possible via the vehicle settings. Those who are on the road a lot or who drive short distances particularly often should not lose sight of the engine oil level.

Short-distance and frequent drivers or riders should check the oil level of their cars and motorcycles particularly regularly — at least once a month. Frequent cold starts in city and short-distance driving could lead to harmful oil dilution by fuel residues, as these do not evaporate if the engine oil does not get really warm. The dilution reduces the lubricating effect. It can be recognized by the rising oil level and requires an oil change. Those who drive or ride long distances regularly — more than 600 miles (1000 kilometers) a month — on the other hand, are more likely to be dealing with higher oil consumption.

When refilling it is essential to use the correct type of oil. It should be approved by the car manufacturer for the respective model. Information on this can be found in the operating instructions and often also on the oil cans. If you do not adhere to it, you risk damage to the vehicle drivetrain and can also have problems with the vehicle warranty. There are around 250 types of oil on the market. 

In addition to regular oil level checks and the use of the right lubricant, compliance with the specified intervals for oil changes is crucial in order to ensure optimal engine lubrication. 

How to check oil levels in a car

how to check oil

1. To measure the oil level correctly, the engine should be warm . However, wait a little after switching off the engine so that the oil can collect completely in the oil pan.
2. Most cars have a dipstick to check the oil level. To do this, open the hood and pull out the dipstick. You can find out where it is in your car in the operating instructions. (Warning: some modern cars no longer have a dipstick, the oil level is called up via the on-board computer).
3. Clean the dipstick with a lint-free cloth or paper towel and reinsert it completely into the opening.
4. Pull out the dipstick again .
5. Using the markings, read off whether the oil level is correct : The minimum and maximum oil level are noted on the dipstick, the oil film should reach at least to the middle between the two marks (more in the direction of the max line), but never be below or above.

How to check oil levels on a motorcycle

Before you check the oil level on the motorcycle, the oil must be warm. To do this, drive around 10 kilometers if the engine is still cold. Then park the motorcycle in an upright position and allow the oil to sink for a few minutes. On some models, the oil level is also measured when it is cold, but usually when it is warm.

  • Many motorcycles have a small sight glass on the right side of the engine. There you can read the oil level directly. Next to the glass you will find the upper and lower markings.
  • In older models, the oil tank is located in the frame, in the swing arm or under the engine. The dipstick is hidden behind a small cap. Pull out the wand and wipe it with a dry and clean rag or cloth. Put the dipstick back in and out and you can read the level.
  • If the level is closer to the lower than the upper mark, it is time to add more oil. Carefully add enough oil until the oil level approaches the upper mark.
  • In general, you should change the oil every 10,000 km .

When should oil be topped up?

The oil level should be between minimum and maximum. Otherwise there is a risk of damage to the engine.If the measured oil film only barely reaches the minimum mark or is even below that, you must top up oil as quickly as possible . The filler neck is usually on top of the engine, where exactly is described in the operating instructions. 

How much oil you have to fill in depends on the fill level and the fill quantity specified in the logbook. As a rule of thumb, there is approximately one liter of oil between the min and max marks. It is better to feel your way slowly before filling in too much. Important: Always wait a few minutes before measuring again so that the oil can settle.

What to do if there is too much oil?

To be on the safe side, wait a few minutes, then clean the dipstick again and check the oil level again. If it is still clearly too high, speak to the trustworthy workshop and discuss how to proceed. This also applies if you accidentally noticeably topped up with too much engine oil . Too much engine oil can be foamy: the lubrication performance decreases and the oil can also get into the intake tract and cause damage.

Measure the engine oil level in your car regularly . If you drive with an oil level that is too low, you endanger the engine. Too much engine oil is also harmful. Modern engine oils are much more efficient than they used to be, but that only applies if you regularly check whether there is enough engine oil available. Ideally, you should check the oil level every time you stop for fuel – regardless of whether it is diesel or gasoline. In any case, before long journeys, especially when going abroad.

Wet sump vs dry sump problems in motorcycles

A motorcycle dealer recently reported to us that he had got a Yamaha with dry sump lubrication into the workshop, which spat oil out of all engine openings, including those that are definitely not intended for this. During the troubleshooting, the mechanic drained 8.5 liters of oil (in words: eight and a half!) That would not have surprised us with a Boss Hoss with a V8 engine, but since most motorcycles rarely need more than 3.5 liters of engine oil, this oil appears -Level record-breaking high.

How could that happen? Sight glasses or dip sticks with markings for measuring the oil level, which can be found on every motorcycle, should actually provide information about the correct fill quantity. Unfortunately, the oil is not always where it can be measured. To understand this, we have to delve a little into the technology of the different lubrication systems of the engine and the engine oil itself.

Today, motor oil is a complex and expensive product that not only consists of the actual mineral or synthetic oil, but also of up to 20% added additives that have to perform a wide variety of tasks. To improve viscosity, we find polyester, such as poly isobutyl in oil, detergents for cleaning engines, corrosion and oxidation inhibitors, friction reducers and foam dampers – a real cocktail.

Some engines are designed as one unit with the gearbox and also have an oil bath clutch. In this case, the additives to reduce the coefficient of friction are reduced and high-pressure additives are added, which make the shear forces of the gear wheels more bearable for the oil. All engine oils have at least one thing in common that they lubricate connecting rod and crankshaft bearings, camshafts and cylinder sliding surfaces and should cool the engine. If the engine runs with too little oil, this leads to increased wear in the absence of adequate lubrication, and even to seizing of moving components.

In the opposite case, if the engine receives too much oil, it loses power because the oil gives the moving parts a not inconsiderable, braking damping. The oil can become foamy when the crankshafts, connecting rods and piston heads hit, reducing its lubricity with devastating consequences. Ultimately, the oil pressure inside the engine increases. This destroys seals or discharges into the air filter via the crankshaft ventilation. This is why the correct amount of oil is so extremely important. Modern 4-stroke engines are supplied with oil via circulating lubrication, which is divided into wet or dry sump lubrication.

The wet sump in motorbikes

With wet sump lubrication, the engine oil collects at the bottom of the oil pan, is pumped from there and sprayed on top of the engine onto the engine parts to be lubricated and cooled. Then it automatically runs back into the oil pan. At an extremely high incline and on long inclines, the amount of oil in the pan could shift so unfavorably that the pump only sucks in air and the lubrication fails temporarily. This undesirable effect can largely be prevented by baffles inside the tub, at least when braking and accelerating, but cannot be completely ruled out.

The dry sump in motorbikes

That inspired the engineers to design the dry sump lubrication. Two pumps are used for this. The so-called feed pump sucks the oil out of the oil pan and conveys it into a separate oil reservoir. You can see this oil container very well on the Harley-Davidson models with a balanced big twin. It is called a horse shoe because of its shape and sits under the front part of the bench. This suction process means that large amounts of oil no longer collect in the tub, hence the name dry sump.

A second pump, called a pressure pump, sprays the oil to the areas to be lubricated and cooled. It then runs back into the tub to be sucked off again by the feed pump. Since the feed pump has a higher suction power than the pressure pump, there is always more oil available in the separate oil reservoir than is really needed and can be sprayed by the pressure pump. This reserve makes a failure of the lubrication system almost impossible, even if the feed pump would briefly suck in air.

Dry sump lubrication is more complex and brings additional weight with it, but apart from the higher operational reliability it allows a flatter oil pan and thus reduces the overall height of the engine. It can therefore be installed in the frame with a lower center of gravity. Because the oil reservoir is preferably positioned behind the engine, it has more space at the top for valves and camshafts.

How to check oil levels with a wet sump motorcycle

With wet sump lubrication, the engine oil level is measured using a sight glass or dipstick based on how high the engine oil is in the oil pan. The impression that there is not enough oil can arise if one does not wait immediately after the journey until all of the oil from the areas of the engine to be lubricated has drained back into the oil pan. A measurement while the engine is running will show even less oil as a significant amount of it in the engine is doing its work instead of resting in the oil pan for measurement purposes.

How to check oil levels with a dry sump motorcycle

With dry sump lubrication, however, waiting doesn’t help either. As soon as the engine is switched off, the feed pump also stops pumping oil into the separate oil container. Everything that now runs back from the engine into the sump can no longer be measured in the oil container. The oil is still there, but it is missing for measurement. The apparent lack of oil often leads to incorrect topping up and overfilling of the engine with oil.

Almost all engines that are operated with the wrong amount of oil have been overfilled, very few suffer from an oil deficiency. The thermal expansion coefficient of the engine oil depends on the type and is somewhere between gamma 0.0009 and 0.0007, depending on the severity and the additives added. This means that with an average engine with 3 liters of oil, an average starting temperature of 15 degrees and an operating temperature of 85 degrees, we can assume a difference of around 120 ccm between hot and cold oil. 

On the dipsticks and sight glasses of smaller engines, that is the amount between the maximum and minimum oil level. Misinterpretations can be the result. The correct oil level can therefore never be at the maximum mark when the oil is cold, unless the mark is incorrectly positioned or the motorcycle is not correctly aligned. Measurements on a warm, but not too hot engine are useful.

The position of the motorcycle is important when taking measurements. A level surface is always necessary. Most manuals indicate that the motorcycle should be leveled on the center stand, a work stand, or by holding on to measure the oil. The latter seems quite insecure and acrobatic, because you usually have to crouch down to measure. It is safer to ask a second person for help.
As is well known, exceptions confirm the rule. With some Harley models, measurements should be taken on a flat surface on the side stand.

While the sight glass itself is unmistakable, the dipstick allows further sources of error. Some dipsticks are unscrewed and should be screwed all the way in again with a cloth after cleaning. Others, however, should only be reintroduced up to the thread. Good for those who have studied his manual, because with a thread length of one centimeter on the dipstick, 1 liter of oil could by mistake go unnoticed in the tub. In general, it is important to read the manual carefully in order to avoid such errors.

If you don’t trust the accuracy of the brands for the maximum and minimum oil level on the sight glass and dipstick, but want to know exactly how the correct oil level is actually displayed on your motorcycle, you can proceed as follows.
Immediately after an inspection, if there is no doubt that the correct amount of fresh oil is present in the engine, a reference measurement can be made. 

To do this, the motorcycle must first be driven about 10 kilometers in a moderate driving style so that the oil reaches an average operating temperature and the oil filter that has been replaced can also fill with oil.

The machine is then positioned upright on a flat surface in a clearly defined position that can be easily found for later measurements. The position of the handlebars also has an influence on the position, especially in vehicles where measurements are to be taken on the side stand. After the engine has been switched off, the engine oil needs a few minutes to drain back into the oil pan. Only now can measurements be taken. Since we can be sure that the amount of oil available is absolutely correct, even if we do not know exactly where the oil is still floating around inside the engine, apart from the measurement point, we get the level for the precisely prescribed oil quantity.

If the level is not in the middle between the maximum and minimum markings, we mark the correct oil level ourselves with a notch on the dipstick or a line next to the sight glass. As a precaution, the process should be repeated. With dry sump lubrication, differences in the amount of oil measured in the reservoir can occur due to the different speed-related delivery rates of the delivery pump.

Remember that the feed pump has a higher power than the pressure pump. However, the feed pump can only transport the oil into the storage tank that has just flowed from the engine into the dry sump.
If the machine idles a little longer before it is switched off, only a little oil is required for engine lubrication and is sucked out of the reservoir by the pressure pump. Accordingly, there is little oil in the engine, but all the more in the reservoir.

After driving at high speeds, the opposite is true. Because of the high need for lubrication and cooling, a lot of oil is sprayed on the working engine parts. After the machine has been switched off, a larger amount of oil runs into the dry sump, from where it is no longer pumped into the storage container for measurement. It makes sense to mark this leeway.

The result of repeated measurements on an engine with wet sump lubrication, on the other hand, should be identical, provided that the oil has been given enough time to run back into the sump.

What you need to know about motor oil

The main task of motor oil in an internal combustion engine and its circuit is to lubricate all mechanical and moving parts. Metal gears, bearing rings and their seats are often exposed to high loads during operation. Lubrication and the associated cooling of the installed parts is essential for long-term and durable use.

The engine oil minimizes the frictional heat that arises when an engine is running.

What does SAE stand for?

The product names such as SAE 10W-40 are explained as follows. The abbreviation SAE stands for the Society of Automotive Engineers. This is a classification society that was founded in 1911 and, in addition to standardizing production processes, also developed viscosity classes for motor oils.

Viscosity is generally understood to mean the viscosity of fluids. This also includes engine oil. The designation 10W-40 can be explained as follows:

  • The 10 means that it is a thin oil. 
  • The larger this number, the thicker the oil is. 
  • The “W” means that the above value applies when it is cold. 
  • The second number indicates an upper limit of the viscosity at 100 degrees – here in example 40.

Generally speaking, you need thin oil in winter and thicker oil in summer. With 10W-40 you can usually get through the whole year without any problems. Because the oil adjusts its viscosity.

How long does engine oil last?

Motor oil has a shelf life of around three years. Assuming the seal has not been opened. In addition, the oil can should not have been exposed to high temperature fluctuations. If in doubt, you should have the oil disposed of at the petrol station, as otherwise there is a risk of damage to your engine.

Diesel fuel also has a limited shelf life. After two years at the latest, the oxidation has progressed to such an extent that there is a threat to the engine. For example, deposits can form on the injection system and solids can deposit on the engine floor. Also read up on how to change the oil in a car.

gerhardt-richter Gerhardt Richter is a writer and a trainer at trade technical colleges, specializing in carpentry, plumbing, mechanics and construction.