Usage conditions and driving behaviour
Full throttle, use which is predominantly of a „stop and go“ nature, or demanding hill ascents cause temperatures and therefore loss due to evaporation to rise.
Oil level in the engine which is too high
For quantities of oil which are too great or if there is too much fuel in the oil due to constant short trips, the crankshaft will dip into the oil sump. But if too much oil is used, increased splashing and therefore more flexing work is the result. As a result, the oil temperature increases.
Incorrect oil quality
It is not without good reason that automobile manufacturers include the ACEA or API specifications of the oils in their operating manuals, or freely share their names. If the specific requirements are not adhered to, e.g. with regard to loss due to evaporation, there is a risk of increased oil consumption. If engine oils are used which are not freely shared, the limit values for exhaust emissions can often not be complied with. Engines of generations Euro V and VI with their complicated exhaust gas treatment systems are particularly affected. Their function is reduced and there is a threat of damage and significantly shorter service lives.
Unadjusted oil change intervals
If oil analyses are not carried out, the oil change intervals stated by the manufacturer or those indicated by the on-board computer should generally be adhered to. In extreme usage conditions, an analysis of the used oil can show that the intervals should be reduced.
Faults in the injection system or valve control
Moving parts of an injection system are partly lubricated via the engine‘s oil circuit. If internal leaks occur, oil can come into contact with fuel in the engine‘s combustion chamber. Even if the exhaust valves open while there is still oil on the wall of the cylinder, partly unburned oil can escape through the exhaust system. This often leads to an increased burden on the exhaust treatment systems. If the number of soot particles in the oil increases due to faults in the injection system or as a result of incorrect valve control, the additives will no longer be able to keep all of the particles in check. The anti-redeposition power of the engine oil decreases, and the danger of deposits increases. The viscosity of the engine oil will also increase, thickening and losing volume. Fail-safe lubrication can no longer be guaranteed, particularly during a cold-start. Fuel consumption rises simultaneously.
Consumption of dirt-carrying additives
All types of engine oil take on a darker colouring after a short while. Their detergent/dispersant additives prevent the formation of sludge and lacquer-like deposits which develop in the form of soot, the products of acid reactions, nitrous gases, unburned fuel residues and water. Dirt is broken down into small particles, suspended in an emulsion and transported to the filter. In this way, the oil ensures the engine is clean and ensures optimal combustion. But there will eventually come a point when the supply of these additives runs out. The anti-redeposition power of the engine oil depletes, and the danger of deposits increases. Fail-safe lubrication can no longer be guaranteed, particularly during a cold-start. Fuel consumption simultaneously rises.
Insufficient piston ring sealing
If worn or broken piston rings do not seal the cylinder piston sufficiently, or if deposits have formed around the oil scraper ring, oil consumption can increase, since the oil which is not scraped off the piston wall and into the oil sump will burn.