Fork oils

finished off my service on the GPx yesterday
and that included a stg head bearing regrease
and new fork oil
the fork oil was changed 18 months ago, 7,500ks ago
and it came out black...
unbelievable how black it was
looks like bad engine oil
filled it with 15w and 10mm higher levels
and that has stiffened up the front very nicely....
so when was the last time anyone changed their fork oil
with their engine oil???
and that included a stg head bearing regrease
and new fork oil
the fork oil was changed 18 months ago, 7,500ks ago
and it came out black...
unbelievable how black it was
looks like bad engine oil
filled it with 15w and 10mm higher levels
and that has stiffened up the front very nicely....
so when was the last time anyone changed their fork oil
with their engine oil???