Someone will tell me if I`not correct but but as far as I know the letter and numbers on Volvos are as follows F10 10ltr F12 12ltr F16 16ltr the following letters are impoised load ie weight on rear bogie (1017) 17t (1020) 20t (1025) 25t and so on that is why if its a 4 wheeler 6 wheeler or 8 wheeler the letters/numbers thing always works. be it F7 F10 F12 F16 the new ones are 13 ltr think they did not put F13 because some peoples thing about the number 13 am I also right that F is Forward control and N Swedish for nose.LOL. 