How to Tell the Difference Between the FSI & the TFSI

Written by luther blissett
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Audi is a German manufacturer of a wide variety of cars, including the iconic RS 8 sports car. While you can identify all Audis easily by their distinctive four-ring grill, differentiating between the Audi FSI and TFSI engines is more difficult. FSI stands for fuel stratified injection while TFSI stands for turbo fuel stratified injection. Because all Audis take advantage of TFSI, FSI or diesel technology, it is possible to tell the difference between FSI and TFSI equipped vehicles by first identifying the model of Audi and then looking for the distinctive marks of each engine type.

Skill level:


  1. 1

    Examine the outside of the Audi for signs that the vehicle is a diesel. If the badges on the back of the car contain "TDI" or "Diesel," the vehicle is not equipped with a FSI or TFSI engine. If the car is missing the badges, open the fuel filler door and look for the word "Diesel" on the fuel cap.

  2. 2

    Look for the word "Turbo" or the letter "T" on the back of the Audi right after the engine size designation. For instance, an Audi A4 equipped with a TFSI engine will have the following badge on the back: "1.8T."

  3. 3

    Open the car's bonnet and inspect the vehicle's engine cover. TFSI-equipped vehicles will have the word "Turbo" stamped on the engine cover adjacent to or below the Audi four-ring logo. If the Audi is not a diesel and is not equipped with a turbo charger, the engine installed is the standard FSI engine.

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