As I remember, I had to replace the valve cover gasket on my 121 at 130,000km during the tune up. There are some signs that you can test whether the mileage is true. But they are not 100% accurate
1.Break pedal-usually car with around 60,000km might have an almost new looking break pedal.But this can be varied. If the driver had used shoes during driving all the time the pedals might wear out faster.Check the right side corner of the pedal.
2.Steering wheel-If the driver hadn’t use a cover, check the top of the steering wheel. (Which means 12 o’ clock of the wheel).Check whether it moves easily when you try to grind it by your hand.
3.Doors-If the doors open in two steps(specially the driver side door) it is a sign that the car is still new
Hi,
Taking into account the mileage, it's acceptable for a small loss of engine oil,.
Yes your choice to go back to a lower viscosity has made it worse,..so check the engine for any leaks and clan the pcv and put a thicker oil.
Good luck,..