I've taken my Audi A4 B7 to the same garage for two years tyres, oil change no problems. Last oil change the filter cap came off after about three months oil everywhere. I took it back they refitted it. I did the oil myself next time no problems then the oil filter cap comes loose after two months. I refitted it tightened it down. Checked occasionally no worries. Checked one evening on the drive all well then drove off the drive twenty yards up the hill the oil cap is off again. I've removed the spring under the cap. I've bought a cap with a built in spring, which I thought it was just a plastic nipple to press on the filters built in spring. I'm considering changing the filter type, with no long tail at the base. Question is am I OK leaving the spring out is the pressure applied necessary or is it the filter type that's incorrect ?