I suspected the fan may not be kicking in
London traffic +hot engine+no fan =oil light
was the rad hot (wet stat open ) at 105 degrees
coolant temp sensor is on the head
You were dead right about the fan not engaging. Haynes says the temperature sensor on the 1.6 is in the thermostat housing.
sorry,yes on the wet stat housing
unplugging the coolant temp sensor should put the fan on high (does on most vauxhalls
) when the engine is running . which is a test to try (takes seconds to do ,will out EML on and throw a code but will reset when plugged back in )
so I presume the thermostat was working all right.
NEVER assume
always test
so my thoughts are, now you have 10w40 semi and a clean filter ,oil will be fine (but please check pressure when your test kit arrives )
it's vital the electric fan works though , when hot ,and what you can check and sort while waiting for the oil pressure test kit .
fan is vital because if the cooling system is not working then when overheating in traffic,the oil light will come on ,followed by blown head gasket ,which ,is dashed inconvenient
and will be a faf to sort on a z16 xep (i know because i stripped the head off one for a mate when he cooked it )