I think Pilot DAR is in the minority with his refusal to use Multigrade oil. Pretty much every commercial operator of piston aircraft I know uses either Red Ram (Philips) 20-50 or Shell semi-synthetic 15-50. Although the latter is more expensive so its use seems to restricted to turbocharged twins.
When I bought my little Grumman AA1B in the late fall 10 years ago the previous owner had used straight 80 oil. he had changed the oil 5 hrs prior to the sale so I flew the oil for another 20 hours. I then changed to 20-50. There was no question that on a typical Canadian West Coast winter day (ie +5 deg C) the engine was easier to crank and showed oil pressure as soon as it started as compared to a few second delay with the old straight oil. If there is any downside with Multi Grade oil I think it is on the hot side. Even though 20-50 is notionally a 100 weight oil on the hot side, engine do run seem to run cooler with staight 100. If the aircraft where based in a hot climate I would change to straight 100 during the summer, particularly for cooling challenged aircraft like the Grumman.
There is a aircraft mechanic at my home field who is widely considered to be an engine savant. He thinks there is no reason to preheat engines using Multigrade oil at temperatures at or above 0 deg C. After working on many hundreds of engines he has found no evidance that not preheating reduces engine life, a feeling that seems to mirror the experience of the UK piston aircraft fleet. Below 0 deg C however he thinks a whole engine heating system (not just the oil) should be used.
As an aside there does seem to be a fairly widespread problem with students and new pilots starting engines when it is cold. I think this is due to a reluctance to give the engine enough prime and is IMO a result of flying schools propagating the urban legands of aircraft which postulate that there is an exteme danger of having the aircraft burst into flame if one ml too much prime is used. At 5 deg C a C 172 needs 2.5 to 3 full shots of prime and at 0 deg 4 shots. An unsuccessfull start (ie the engine fires but then dies) will require more prime before cranking.