This is almost as good as 'what primer do you use?' on the RV forums
Modern multigrade and all oils which have the Lycoming recommended additive in are fine. Camguard will, does, maybe provide more protection to Lycomings, however the most important thing with these engines is regular use and regular oil changes.
Let us split this into two - Lycomings suffer from camshaft dryness, Continentals can suffer sticky valves. Both can benefit with regular oil changes. Camguard can help on Lycomings for dryness, Marvel Mystery Oil or Redex in the fuel can certainly help the smaller Continentals with sticky valves.
By regular use, I mean fly it, don't ground run it. Ground running will not get the oil to boil off the moisture and you will roast your back cylinders because of lack of airflow. Fly it, even if it is just 30 mins of circuit bashing. We fly for fun, so have some fun !
Regular oil changes - this means calendar as well as hours. Our engines are dinosaurs, they were developed as ditch pumps and tractor engines back in the 30's and not much has evolved since. That means woefully low compression ratios, lots of piston blow by and acidification of the oil. Our fuel contains lead which gets trapped as salts in the oil which also adds to the problem. The answer is really simple, schedule a calendar or hours based oil change system. Every 4 months or 25 hours in low use aeroplanes. As owner, you can do it yourself as permitted maintenance and you don't necessarily need to change the filter - it is the nasty products in the oil you are after. Filter at 50 or annual, oil every 25 hours or 4 months. Cost - about £35 - 80 using one of the usual suppliers.
Camguard - it can help, but I am not sure it is essential.
I add a little excitement, a little spice to your lives and all you do is complain - Q