High oil consumption, as a rule, signals a malfunction in the engine (unless the engine is prone to high consumption). Any car owner can solve some of these problems, but most of them need special tools and service station conditions.
Possible reasons for engine oil consumption are elementary: wrong oil is filled, oil filter is leaking, valve cover gasket is leaking. And serious and demanding reasons to eliminate are: wear of piston liners, clogged breather, worn oil-reflecting caps, leakage through the cylinder-head gasket or crankshaft oil seals.
What is normal engine oil consumption?
Every internal combustion engine has such a concept as «natural oil consumption». That is, the oil naturally evaporates during the operation of the engine (this is especially true for mineral oils). And for some engines (often it is the motors of BMW, Volkswagen, Hyundai, Toyota, Subaru), because of its design increased consumption is also the norm. Therefore, it is necessary to monitor the oil level and perform periodic oil replenishment on a regular basis.
The oil consumption rate depends on the type and condition of the engine. For the majority of new atmospheric petrol engines, allowable oil consumption is 25-40 grams per 1,000 km (0.025-0.06% per 100 liters of consumed fuel). In V6 or V8 engines the consumption may be up to two times higher. For turbocharged petrol engines, in a new condition, the norm is about 80 grams per 1000 km of run.
Therefore, for a car with an engine with serviceable two- or four-year operation to add 100 grams of oil after 1000 km mileage is quite acceptable flow rate. A gasoline engine of a car that is more than 5 years old can take from 400 to 600 grams. And if the appetite has increased to 800, it most likely needs repair.
Sometimes automakers write in the service manual that even a liter of oil can be considered normal, but it is not absolutely so. High consumption is acceptable in severe operating conditions or only for a turbo engine (a worn-out engine with a turbo can consume up to 1.5 liters per 1,000 km).
As for the diesel engines, they will have higher consumption per blowout than the atmospheric petrol engines. So, it is considered that the norm is the value of about 30… 50 grams of oil per 100 liters of fuel. The critical value is 2 liters per hundred liters of diesel fuel.
Using the calculator, where the engine oil consumption formula is used, you can calculate the consumption rate of your car engine:
Why engine using too much oil?
The basic problems which entail the necessity to add oil to the engine are:
- Improper oil. You must fill your engine with the viscosity and tolerances recommended by the engine manufacturer.
- Severe use of the engine. In particular, frequent work at high revolutions. Its temperature rises considerably, and it needs more oil for lubrication and cooling. Remember that more oil is consumed during the cold season. This is due to the way crankcase ventilation works.
- Infrequent oil changes. Oil does not always last for the length of time specified by the car manufacturer. Its maximum service life is no more than 15 000 km, after which it begins to burn down more intensively.
Observance of these simple recommendations will allow you not only to reduce oil consumption, but also as a whole to prolong the term of operation of the engine and its separate parts.
There are two reasons for the drop in oil levels — oil consumption and leakage (high flow rate). So, if the oil is chosen correctly and the driving mode is moderate, there should be no excessive consumption with a serviceable engine. But when, under the same conditions, the lubricant is losing, it makes sense to search for the cause of the fault.
What are the reasons of oil consumption and how to fix?
There may be the following reasons which tip you, on how to fix excessive oil consumption:
Reasons for increased oil consumption car: video
- Wear of the gasket under the valve cover or engine crankcase
- Oil is not suitable for the engine
- High crankcase pressure
- Worn oil caps
- Wear of oil seals
- Puncture of the cylinder-head gasket
- Wear of piston liners
- Cylinder wear
Valve cover gasket wear
Typically, leaks are visible at the bolt joints. Aging is due to natural causes, but if it has been replaced recently, either the engine was overheated or the bolt tightening order was violated during installation.
The solution to this problem is to try tightening the bolts to increase the tension (preferably with a torque wrench). But it is better to put a new gasket, following the instructions for its replacement.
Wear of the oil pan gasket
Wear of the oil pan gasket
The situation here is similar to the previous one. The engine sump gasket can be seen when inspecting the car from below. Its material will eventually harden and it loses elasticity.
The solution to the problem is to try to tighten the fixing bolts or replace the gasket completely.
Inconsistency of viscosity or oil tolerance requirements
If an engine is designed to use low viscosity oils in it, and a more viscous oil is poured into it, its piston rings become incapable of completely cleaning the grease from the walls of the cylinders. The consequence is that the oil gets into the combustion chamber and there is increased oil consumption. In older engines, it makes sense to use thicker oil as the mileage in the engine increases because the fluid oil can enter the combustion chamber under the scraper rings.
The problem will be eliminated if you adhere to the recommendations of the vehicle manufacturer, and pour into the engine oil they require, but only if the condition of its parts does not have critical wear.
High crankcase pressure
1. Centrifugal oil separator; 2. Crankcase ventilation valve; 3. Discharge air cooler; 4. Turbocharger; 5. Exhaust gases.
As a rule, the crankcase pressure increases at considerable engine wear, elements of its cylinder-piston group. Therefore it is necessary to perform diagnostics of the engine condition, the geometry of cylinders, state of their coating and so on.
The first thing to do is to check the crankcase gas valve (cap). If it is defective — it is necessary to repair or replace it. Also, clean the crankcase filter (if provided).
Usually, with defective crankcase ventilation, there is an increased oil burn-out (high fouling), compression decrease, fuel combustion deterioration, oil life reduction (quick oil contamination).
Wear of oil sealing caps
These rubber parts are small gaskets on valves, whose job is to keep oil out of the combustion chamber. If they lose their elasticity (natural process or as a result of frequent overheating) there is a loss of oil that burns together with the fuel. This can be understood when starting the engine by the blue smoke from the exhaust pipe or by the soot on the exhaust valves (you can see if you drop a special chamber into the spark plug hole).
Worn crankshaft and/or camshaft seals
Oil seals, which prevent oil leakage from the engine over the shafts, eventually wear out or get damaged as a result of overheating and mechanical contact with foreign objects. You can tell if there's oil leaking under the oil seals by looking for wet spots around the shafts. And if we are talking about the rear crankshaft oil seal, which enters the gearbox, you will have to inspect the gearbox from below or you will see a puddle of oil under the car.
To correct the problem, the oil seals should be replaced. As a temporary solution, you can try using a special oil additive that will soften all the rubber parts with which the oil is in contact in the engine.
Damaged cylinder-head gasket
Damaged cylinder-head gasket
A cylinder-head gasket leak can lead to many problems, including the engine eating oil. Damage occurs as a result of the seal and the result of this problem will depend on the place where it failed (may leak antifreeze, leak oil, or mix them).
There are two ways to diagnose the problem. The first is to perform a visual inspection of the unit looking for oil leakage from the fixing place (from under the bolt) and around the perimeter of the gasket, and maybe the oil starts turning into a milky mass. The second is to check the condition of the coolant. If it is broken, there will be oil stains in it. In some cases, white emulsion appears.
What to do in this situation? — Perform replacement of the cylinder head gasket. As a rule with such a problem, people seek help in service, because it will be necessary to observe the sequence of bolt tightening and tightening force. In addition, the procedure itself is labor-intensive, so it is expensive.
Wear of piston liners
The rings wear out naturally during operation as a result of constant friction against the cylinder walls. When the wear reaches a critical value, the rings do not cope with their work and some of the oil is burned together with the fuel. Ring wear can also occur due to a drop in coolant level. Because of this, the engine gets very hot and the rings, as motorists say, «lodge».
Such a failure can be diagnosed indirectly by a change in the color of the exhaust gases and a change in their smell, the smell of burning oil is added to it, and the blue smoke is constant, unlike the wear of the valve seals.
Repair in this case is quite costly, both in terms of the amount of work and money. It requires disassembling the engine and replacing the oil rings.
Engine cylinder wear
But there may be a less costly reason — caking of rings and oil channels. This situation occurs if the engine has been running on bad (or unsuitable for it) oil for a long time. In this case, the increased consumption of engine oil is ensured, but it can be solved much easier — by cracking with a special liquid.
Engine cylinder wear
This cause is associated with the natural wear of the cylinder block. It is most common in high mileage engines. In this case, oil enters the combustion chamber because the rings (even if they are in good condition) are loose against the walls of the cylinder block. The oil leaks into these cracks.
Similar to the previous point in this case there will be blue smoke coming out of the exhaust pipe. The amount of «eaten» oil depends on the degree of the cylinder walls wear.
Repair in this case is also quite costly. In the best case it will be necessary to rebuild a block, returning cylinders to a correct geometric shape.
Typical causes of increased oil consumption for diesel and turbo engines
In addition to the above causes (which are relevant to both gasoline and diesel engines) in diesel engines, there is one special — the wear of the high-pressure pump parts. As a rule, their lubrication and cooling occur through a common oil system. Due to component and/or gasket wear, engine oil can enter the engine combustion chamber.
Indirect signs of such a failure, in addition to an increase in the amount of oil consumed, is the appearance of thick black smoke from the exhaust pipe (similar to the blue smoke in gasoline engines).
If the car is equipped with a turbine, the pressure increase may be caused by its failure. It is not difficult to diagnose turbine failure, usually in such cases its oil seal or bearings will fail (oil will leak from the turbine).
Cars with old design turbochargers have their own specifics of work, due to which excessive oil consumption is possible. For example, the old turbines were cooled by the engine lubrication system. Accordingly, if the turbine breaks during operation (the bearings break), it can distill oil from the engine through the bearings. And depending on how broken the turbine oil consumption may be quite high, and may be up to 1… 3 liters per 10 thousand kilometers.
Also, partial failure of a turbocharger may cause an increase of crankcase pressure. And this in turn leads to oil entering the cylinders directly into the fuel injection through the crankcase ventilation system.
The repair requires replacing worn turbine components. In the most critical cases, a general turbine replacement is performed.
Engine oil consumption in a new car
In engines that have just come off the conveyor line or in which a complete overhaul was carried out, all rubbing parts are not yet perfectly lapped. Because of this, the first few hundred kilometers of run the engine works in the running-in mode, when there may be microscopic gaps between the parts. Exactly through these gaps the oil leakage is possible. The situation will normalize when the parts are lapped and the engine can be operated at full power.
Do not forget that during the running-in period it is necessary to drive sparingly, and not to give the engine high loads (including high revolutions).
How much engine oil consumption is normal?
For modern cars, the normal oil consumption level is under 0.05%. If your vehicle engine is old, the norm can be a little higher.
What causes high engine oil consumption?
Excessive oil consumption is a mechanical failure. It can be caused by the blown valve cover gasket, leaks of the main seals, or leaks from crankshaft seals.
How do you fix high oil consumption?
You have two ways to fix a high oil consumption: 1 — fill in special additives for oil-burning reduction; 2 — increase oil grade. Instead of using 10W-30 oil, fill up with 10W-40 or single-grade oil. Use 10W-40 oil in summer and 10W-30/10W-20 in winter.