I had a warning saying low oil put in 1.25l drive to workshop. Something along those lines. Went to Halfords . They said I needed 0 20 oil so put 2 litres in. Now I have never used that oil before. Anyway after putting in the oil I had a fault warning when checking the oil level. Opened boot tightened cap and now am getting oil full warning reduce oil. I don't think I have too much oil as last time I looked I was just under half way on the oil level meter. I have no idea what is goibg on. How do I actually reduce oil. Does the S4 have a dipstick for manually checking levels