I have had Volvo's for years and have had 4 740's including the one I have now and I use nothing but Castrol 20w50 in all of them, yes even in the winter. Also I have 2 740's now with over 300,000 miles on them.
No it's water cooled, but it is supplied with engine oil pressure for the bearings.
4 quarts in the non turbo so should be around the same
Volvo recommends 10w30 full synthetic oil.
With new oil filter, four quarts.
5W-30 in warmer climates, 10W-30 in colder
Right above the oil pan in the center of the block.
4 quarts. always make sure to "read" the oil dipstick.
Castrol 20w50. I have had two Volvo 740s and have been using it for years. In fact, my brother, sister, and father, all of whom drive Volvos, also use Castrol 20w50. While the oil type is important, it is equally (if not more) important to use Volvo (or Mann) filters consistently. I change my oil every 2,500 to 3,000 miles.
Volvo recommends using a synthetic oils that is 30/5. They have 30/5 oils for vehicles over 150k miles that work just fine.
Engine Oil; SAE 10W 30 to 15W 50 or API SG/CD Automatic Transmission; Dexron llD
The oil to turbo is from the crank case. period no special reservoir. If you want to change the oil for your turbo simply drain the motor oil. I change my oil & filter on my '93 740 hotted up 3K miles even though Volvo says 5K miles No problems
Use the exact weight your owners manual recommends. Any major brand will work just fine.