The original was likely a 92C (198F) which is what Volvo specify in the owner's manual of our 1994-940. The 87C (189F) was used in Turbo engines. Wahler is what I have found in the Blue box (with a Volvo logo imprinted) when buying at the dealer, so we can assume it's a good quality unit.

Since a 180F (82C) is not mentioned, I would guess the factory thought it was too low a temperature for optimum fuel economy and emissions? Consider also that a cooler running engine is more likely to have sludge buildup and oil dilution from combustion byproducts that don't evaporate off as quickly.

If your cooling system is in decent shape, there should be no worries with either the 87 or the stock 92. I run the 92 in all three of our red-blocks.
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Bob: son's 81-GL, dtr's '94-940, my 83-DL, 89-745(V8) and 98-S90. Also 77-MGB and some old motorcycles.

The temp gauge has a circuit board that keeps the needle mid way- even though the actual temp may be a bit lower or higher than the middle might indicate.

I placed a lower than stock T-stat in the wifes 940. It stays in the middle mostly, but at times it is actually a bit lower than the mid point. I guess that is OK, but there is a point that if a car runs too cool, mileage suffers.
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' Of all bad men religious bad men are the worst. '' (C S Lewis ; on Evil Men) 89 764 (170K), '94 940T (265K), 92 245 (150K)