Dear All,
My friend's car is travelling on highways in China daily.
Recently found whenever it going faster than 120km/h, the oil pressure warning lamp comes ON (in yellow color). Oil pressure gauge needle functions...

Performed these:

Replaced engine oil & filter
Replaced the oil pressure sensor unit

What else can I trace?

Appreciate any tips or comments about this.

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'74 W114 230.6
'87 W201 190E 2.3-16
'97 W210 E320 Avantgarde