The Most Common Questions About Engine Oil Consumption

In this article our expert consultant, Stevan Dimitrijevic, continues addressing the issues of regular engine oil consumption, what causes higher consumtion, when to consult a mechanic and other interesting questions that we, as drivers, often come across.

If you missed the first part of this text, you can read it here.

Questions

• How much oil does a car engine normally consume?
• What does engine oil consumption depend on?
• If oil needs to be added, which type is the best option?
• What is the limit to engine oil overconsumption and what do we do if it happens?
• What are the reasons for engine oil overconsumption?

It may seem that there are exact, precise and concise answers to these questions, but the truth of the matter is that there is a slight problem - there are no answers which apply to all vehicles, especially not cargo vehicles, which represent a completely separate subject.

 

The Regular Engine Oil Consumption

Internal combustion engines, when working normally, consume small amounts of oil. Engine oil consumption is usually expressed as dl/1.000 km (deciliters per 1.000 kilometers). Given the small engine oil consumption, it (oil consumption) cannot be determined accurately at less than 1.000 kilometers. What’s also relevant is the engine oil consumption between 2 oil change intervals, which, for expert and scientific research purposes, is often expressed as g/h (grams per engine hours) or, to be even more precise, as g/kWh.

The usual passenger cars’ engine oil consumption varies between 0.05 and 3 dl per 1.000 km. It is often stated that it represents from 0.2 to 0.6 percent of the fuel consumed, but there’s been a change regarding this. Near the end of the last century, the aforementioned ratio was from 0.1 to 0.5 percent of the fuel consumed, while nowadays the ratio is along the lines of 0.05 and 1 percent of the fuel consumed.

 

The best definition is that normal engine oil consumption is the one recommended by the manufacturer, but you can find this information only in the form of an upper engine oil consumption limit. Anything less than 5dl/1.000 km is no reason to worry, but this limit usually represents a sign telling you that you need to have your car looked at before the scheduled date (this applies to all cars). If the aforementioned engine oil consumption continues to last and doesn’t get back to normal, it’s a good enough reason for you to perform an engine oil check-up at every 500 kilometers or once a week.

Certain car engines, even new ones, have oil consumption of around 5 to 6 dl/1.000 km, and sometimes even more than that. However, these are special cases and this kind of engine oil consumption can be tolerated only if there’s a written notice acquired from an official car service (engine manufacturer). There are a lot of engine oil consumption parameters, but it is certain that its increase is caused by an increase in RPM (revolutions per minute), and even more by the engine power (torque). Of course, different engines have different oil consumption, but the same applies to them.

What else Does Engine Oil Consumption Depend on?

A combination of a high RPM range and the same torque can cause an increase in the engine oil consumption 2 to 3 times. On the other hand, a combination of the same RPM range and different levels of engine strain (e.g. incline vs. flat surface or decline, especially in different gears), the consumption can be increased 5 to 6 times, which means that, given both of these parameters, the engine oil consumption can go up as much as 10 times. This further means that driving conditions can cause an increase in the engine oil consumption significantly compared to the average one.

Adding the Right Type of Engine Oil

It is certainly the best option to add the same engine oil as the one that’s already inside your engine, but any kind of engine oil with the same or as-similar-as-possible specifications will do the trick in the long run, such as the 5W-30 engine oils, which meet the manufacturers’ ACEA C3 standard, or if you add C3 to C2, C4 to C3 or C2 to C1. Of course, you should avoid different specifications, but any difference less than 10% is not something to be worried about, especially if the oils belong to the same type - ACEA A/B or C.

         

In special cases, such as low oil pressure, you won’t be able to proceed with your journey, so if the same type of oil (or similar) as the one that’s currently inside your engine is not available, add the most similar one, even if there’s a big difference between the 2. For example, add 10W-40 to 5W-40, API SL to SM or SN…Of course, in that case, especially if a larger amount of oil, which exceeds 20% of the oil inside the engine, has been added, you need to make your oil change intervals more frequent.

Adding Engine Oil in Between Oil Change Intervals

It is perfectly normal to add a small amount of engine oil in between 2 oil change intervals. Most of the time, it’s no more than 1 liter, but it can be more. This depends on the vehicle model and is usually stated in the car instruction. Prior to going on a long trip, make sure that you bring 1 liter of engine oil with you, especially if your vehicle has reached an advanced age.

 

The Engine Oil Overconsumption Limit

In the case of small engines (up to 1.5 liters), the usual upper oil consumption limit is from 4 to 6 dl/km. When it comes to bigger engines (up to 1.8 liters), especially if it’s a turbo engine we’re talking about, its oil consumption can vary from 6 to 8 (or even 1 l) dl/km. At first, it seems like a lot, doesn’t it? But have in mind that this is the maximum and not the average engine oil consumption, which suggests severe driving conditions, such as driving on the highway and rough surfaces.

Mixed driving is characterized by 2 to 3 times smaller engine oil consumption, which represents the upper limit. It means that the engine shouldn’t consume more than 2 or 3 liters of oil per 15.000 kilometers. If the engine consumes 5 dl/1000 km or more on a regular basis, even in severe driving conditions, you should pay a visit to a professional car service to determine the reason. It is definitely not normal for you to have to add 2 or 3 liters of engine oil per 5.000 kilometers.

The Reasons for Engine Oil Overconsumption

Before you decide to drive your car to a professional car service, make sure you check on your own whether there are any traces of an oil leak, that is, whether there is an oil paddle under your car, seeing it as these are useful pieces of information for the mechanics. Don’t tolerate engine oil overconsumption for more than a couple of weeks, especially if it keeps increasing, because it might be suggesting engine issues.

 

There are a lot of reasons for engine oil overconsumption, so it’s difficult (practically impossible) to determine the cause without going through a thorough check-up at a professional car service. Aside from a potential seal leak, which can be a secondary reason (another engine problem leads to it), and engine exhortation (this applies to any vehicle older than 10 years or with 200.000 kilometers on it), the most common causes are related to engine problems which require a professional car service’s intervention.

There are things you can check on your own, such as the condition of the crankcase (the sealing gasket might have gone hard, thus causing capillary leaks, or is simply damaged), as well as whether there are any oil filter leaks (poorly installed, damaged or with defects).

We hope that you’ve found this article useful. For any questions, unknowns and suggestions you may have, please, feel free to contact us.