Dave,

If by the next white mark, you are saying it has reached 100C (white mark at 80C and another at an unlabled 100C) then that is a little higher than expected for stop n go with the AC on.....ALTHOUGH, it's NOT so hot that you need to worry about engine damage.

But....100C in stop n go on 80F days, IMHO, cerainly warrants having the
cooling system inspected. Could be something as simple as needing a new thermostat.

__________________
Chris
1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)