Engine Audi AAT

The 2.5-liter Audi AAT 2.5 TDI diesel engine was produced by the company from 1991 to 1997 and was installed only on two models of the concern: with an index of 100 or a similar A6 in the C4 body. This five-cylinder power unit is famous for its high reliability and long service life.

The EA381 series also includes: CN, AAS, AAT, 1T, AEL, AHD, BJK, BJM.


Production years 1991-1997
Displacement, cc 2460
Fuel system direct injection
Power output, hp 115
Torque output, Nm 265
Cylinder block cast iron R5
Block head aluminum 10v
Cylinder bore, mm 81
Piston stroke, mm 95.5
Compression ratio 20.5
Features SOHC, intercooler
Hydraulic lifters yes
Timing drive belt
Phase regulator no
Turbocharging yes
Recommended engine oil 5W-40
Engine oil capacity, liter 5.2
Fuel type diesel
Euro standards EURO 2
Fuel consumption, L/100 km (for Audi A6 1995)
— city
— highway
— combined
Engine lifespan, km ~550 000

The engine was installed on:

  • Audi 100 C4 (4A) in 1991 – 1994;
  • Audi A6 C4 (4A) in 1994 – 1997.

Disadvantages of the Audi AAT engine

  • One of the most reliable diesel engines of its time rarely worries its owners;
  • Most of the problems are associated with malfunctions of the Bosch VE37 electronic injection pump;
  • The aluminum cylinder head is afraid of overheating, it quickly leads mating surfaces;
  • Replacing a timing belt with rollers is expensive, but when it breaks, the valves always bend;
  • At high mileage, the turbine, mass air flow sensor and hydraulic lifters may require replacement.

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