Question, rpm idle speed under light load variation

[ahh911]

1981 sc, stock, runs terrific, but I've one irritant.

Question,
If I adjust the rpm to 1000 while hot, then I become load dependent at idle when hot. Idle with fog and main lights, between 800 and 900. Idle with no lights and clutch pedal down is 1000rpm, clutch engaged is 900rpm thereabouts, (It's been a while since it was in the 80F range). So I've been load dependent only when hot.

Lately I've lowered the rpm while hot till lights w fogs, and or clutch in or out makes no difference to the rpm at all. That rpm is ~ 750. When it's warm it will creep up to the 850rpm range and still hold solid.

Oil pressure is slightly over or around 1bar, as when the oil is hot the rpms track up so the pressure stays roughly just above 1bar at idle of course.

What is the issue with running at 750rpm if the oil pressure is at a bar? I thought the 964's had an 800rpm idle. why not the sc?

Thanks,
Phil