Q:
A: I think by speedo, you mean speedometer. Not speed. Therefore, the fuel or the air filter has nothing to do with it. The 306 is an older model from 1993---. Therefore it still has a speedometer cable and not the newer electronic speedometers. However, I may be wrong here. There was a change in the 306 model when it first had 13 fuses in the fusebox. Later the same 306 changed to 30 fuses in the fusebox, and then it could have received an electronic speedometer???? (just like the 206) IF YOU HAVE the older, 13 fuse model, then you DO HAVE a speedometer cable that has a square plastic end, that fits into a square plastic hole behind the instrument panel. I believe your OLD car has worn down the plastic corners on the square shaft, and at high speeds it doesn't turn the square speedometer shaft. THANK YOU KEVIN !