This 4,5,6 refers to which series.
The 4 series was produced in Europe from 1995 to 2004. It has 9,11,12,14,16 liter engines. shown in the model name with a number constructed by the cylinder volume in litres followed by the generation of truck this way a 14-litre engine in the 4-series will be a 144. The letter, following the number describes the chassis type, but in the 4-series this code changed compared to former series (L, D, C and G in 4-series vs M, H and E on the 3 series). The 3-digit number on the opposite corner in the front stands for horse power. This ranges from 220 to 580 hp. Sample; 164L 480 V8 thats mean 16 liter engine 4 serie and 480hp v8.
The 5 and 6 series is a model with different body types with the codes r1, r2 and r3, produced from 2004 to 2016. With the 5 serie, engines in euro 4 euro 5, with streamline euro 6 norms were produced. Scania's maximum engine power in the 4 series was 580, in the 5 & 6 series it was 730. Between 5 and 6 the grill and bumper changes are almost identical. Scania has also emphasized aerodynamics in the streamline model and changed the deflectors. Between the 4 and 5,6 series there are huge differences in exterior design, interior design and engine. Scania even released special models like Silver Griffin in their streamline models.
Scania produces the S & R series from 2016 to the present day.