Largely - yes. I think there might be a minor increase in oil temps with increasing ambient temps. The coolant can only cool the entire engine indirectly. My 2004 Subaru WRX manual recommends the use of 30, 40, 20W-40, or 20W-50 when towing a trailer or in "desert areas" or "high temperatures", even with a water cooled oil cooler standard. The standard US recommendation is for 5W-30,
10W-30, or 10W-40.Of course there's the worry about how long it'll last if the cooling system fails.
Some people swear by it. Others swear at it. :)