I accidently put 6 litres of unleaded in the tank than filled it up with 50 litres of diesel. I drove 55 miles motorway home. The car seems to drive fine - however, do you think it's safe to continue to drive or should I have the tank drained tomorrow? If so, should we take over 50% out or do you think it should be completely drained? Would adding lubricant make a difference?