Oil analysis over the years
Since 2013 when I bought my first RV, an RV-4 and started flying and maintaining my own airplane, I wanted some analysis behind my decisions. Oil analysis supported running that O-320 well past TBO, I think it is still humming along nicely for the new owner at over 2500 hours.
I started using Phillips 20W-50 with CamGuard added. I did a lot of reading and listening to those that claimed to know oil. I change my oil at the interval recommended by Lycoming, to remove the contaminants in the oil (lead, moisture, etc) and send off a sample to Blackstone.
The last 8 years of oil changes in four different engines has consistently yielded these layman's casual observations:
1. Blackstone reports excellent wear based on the metals and quality of the oil found in my oil samples, usually after about 25-35 hours on the oil average. After I own and fly regularly, then change the oil regularly, it is amazing how the oil samples show how engines settle in consistently with this care procedure.
2. The Phillips multi-viscosity seems to be easy starting and consistent all year round. Each engine seems to run about 180*F though it takes a bit longer to get there in the winter in the Cub. The RV is getting an adjustable oil cooler vane soon, but in the past I've simply covered about 2/3 of the oil cooler with an aluminum plate I can insert during a fall oil change and take it out again during the Spring oil change.
3. No synthetics. Maybe the videos from Mike at Savvy Aviation explain it best... the lead in our engines from piston ring blowby is not compatible with any synthetic oil. I had a choice to try to find MOGAS or simply not run synthetic or semi-synthetic oil. I stay away from Aeroshell and Exxon oil that contains any synthetic for that reason.
4. A nice side benefit is that Phillips is widely available and a couple dollars per quart cheaper. I don't mind changing my oil and filter every three months. I get to take a look under the cowl and keep an eye on my engine since I fly IFR, over mountains and occasionally at night.
I hope those are quantifiable and measurable reasons why I use the oil I use. If we ever get a no-lead option that works with angle valve engines or at least MOGAS more common at my local airports (South Carolina) for the lower compression engines, like my wife's J-3 Cub with the A-65, then maybe that engine could benefit from a synthetic or semi-synthetic.