The 88 and 92º thermostats weren't used by Volvo until the 240 came in with the B21/23. B18/20/30 used either 77 or 82º. Back in ye olde days, it was normal to change between the 2 temps for summer and winter along with different single weight oils. A cash cow for the garages, although the frequent oil changes didn't do the engines any harm. Multigrade oils changed all that and depending on where you lived, changing the thermostat also happened less often. An 82º thermostat is fine. If you overheat you have other problems, likely a clogged up radiator, or easier to fix, poor sealing rad caps. Yes. the water pumps with the cast impellors are a bit more efficient than the pressed steel ones at idle but when driving the difference is negligible. Again, if there is a problem, check the rad. B18 engines with the alcohol expansion temp gauges will show the temps rising for a while after you switch off the engine due to heat soak. B20 with the electric gauge will also heat soak but the gauge will go back to zero when you switch off.
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