These codes are Volvo engine type designations. The first letter indicates the fuel type: B stands for petrol (from the Swedish word Bensin) and D stands for diesel. The first digit is the number of cylinders, and in all the codes you listed it is 5, meaning they are inline‑five engines. The next two digits represent the engine displacement: 24 means 2.4 litres and 25 means 2.5 litres. The fourth digit is the number of valves per cylinder, which is always 4, so each engine has a four‑valve‑per‑cylinder design. The suffix letter tells you the induction method: S means naturally aspirated (from Sug) and T means turbocharged. The final number or numbers at the end are tuning variants within the same engine family; generally a higher number indicates a later or updated calibration, though the exact differences can include power, torque, emissions, or software settings. For example, B5244S4 and B5244S5 are both 2.4‑litre naturally aspirated petrol engines but with different outputs, while D5244T8, D5244T9, and D5244T13 are different tunes of the 2.4‑litre turbo diesel. Similarly, B5254T3 and B5254T7 are both 2.5‑litre turbo petrol engines but with distinct performance levels, ranging roughly from 230 to 250 horsepower depending on the version. These engines were used in many Volvo models from the early 2000s, including the S40, V50, C30, S60, V60, XC90 and others.
