I have run conventional Valvoline 10W-30 and have for probably 40+ years... never a single engine failure. Today's conventional motor oils like from Valvoline, Mobil, Shell, Castrol, Pennzoil etc. are superb and I'd run any of them and know my engines are all being extremely well protected.
And contrary to what some marketing departments would like us to believe, a synthetic motor oil is not needed to protect our engines. Only if I lived in an uber-cold area like North Dakota, Alaska, Buffalo NY, etc. would I pay extra for a synthetic motor oil during the winter which has been shown to be worth the extra $$$ in those extra-cold conditions.