recommend using Aeroshell W100 in the summer
Excellent advice. I really don't like running multi-grades in the summer in private aircraft aren't flown every day, because that multi-grade oil - which is thin at room temps - runs off the engine much faster than straight grade, and can result in more corrosion and metal-to-metal at startup.
The expensive multi-grades are fantastic for Canadian winters - I personally prefer Aeroshell 15w50 - it has the Lycoming LW16072 extreme pressure additive which is required by AD for the infamous "H" engines, and is good for any Lycoming camshaft!
But during the summer, I like to run Aeroshell W100plus which unlike W100 also has the LW16072 in it. It's cheaper than multi-grade, and protects against corrosion better in the summer for infrequently-flown aircraft that sit unused for a week or two.
If it gets really, really hot - OAT 30C to 35C - I like to start topping up with quarts of W120 (sae 60W) to try to keep the viscosity at the higher oil temps. A half and half cocktail of W100plus and W120 will give you an SAE 55W with some LW16072, which is a pretty darned good oil for hot wx for a flat engine.
When you start to see 250F on the oil temps - anyone else here do banner tow, or jumper dumping? - W100 is the absolute minimum viscosity you want to use, and W120 is better. These straight grades are cheaper than multi-grade, and withstand extreme temps better. Hard to argue with that choice.