What are the reasons for Audi CUH engine burning oil?
3 Answers
Audi cars burning oil is usually caused by the use of unqualified engine oil, the engine cylinder block material being cast iron, piston rings sticking due to carbon deposits and reduced elasticity, decreased cooling system efficiency of the engine, contamination of the crankcase ventilation pipeline and solenoid valve, among other reasons. Introduction to oil burning: "Burning oil" refers to the engine oil entering the combustion chamber of the engine and participating in combustion along with the air-fuel mixture. Hazards of burning oil: The phenomenon of "burning oil" in vehicles can cause the oxygen sensor to fail prematurely, leading to increased carbon deposits in the combustion chamber, unstable idling, lack of acceleration power, increased fuel consumption, excessive exhaust emissions, and other adverse effects. In severe cases, insufficient engine lubrication can cause irreparable damage to the engine or even render it unusable, significantly increasing repair costs and posing potential safety hazards.
As an owner of an older A4L, the oil consumption issue with Audi's CUH 2.0T engine is all too common. My car burns about one liter of oil every 2,000 kilometers. The main problem lies in the design flaw of the piston ring oil return holes in the second-generation EA888 engine. When the oil rings get clogged with carbon deposits, they can't effectively scrape off the oil, which then enters the combustion chamber and gets burned. Additionally, the low efficiency of the oil separator allows oil vapor to enter the throttle body along with the exhaust gases. To fix it, I replaced the piston rings with improved wave-style rings and also changed all the valve stem seals during the repair. For regular maintenance, frequent oil changes are essential. I use 0W-40 viscosity oil and make sure to change it within 7,000 kilometers.
Having worked on many Audi engines, oil consumption typically stems from three key issues: first, piston ring sticking leading to ineffective oil scraping; second, aging valve stem seals causing oil leakage; and third, ruptured diaphragm in the PCV valve. The last Q5 I repaired was burning 1.5 liters of oil every 1,000 kilometers after 150,000 miles, with cylinder wall scoring upon disassembly. Focus on checking for oil residue in the exhaust gas recirculation tube and whether the oil separator pressure is normal. The simplest diagnostic method: blue smoke during cold start indicates valve stem seal problems, while smoke during acceleration is likely a piston ring issue.
