Back when h2ofwlr was startin to use a car instead of the old horse and wagon :laughing: they only had single grade oils. Now days we have multi-grade oils for use in engines but the single grades will still work just that for the newer multi valve and overhead cam systems the multi grades provide faster lubrication to these components as they flow more readily at lower temps. A 5w30 oil will start protecting you engine from wear faster than a 10w30 will. Now as for the adding of the single grade oil to your vehicle it won't hurt it. BTW I work with lubricants every day as that is my main job to maintain the gearboxes and hydraulic systems in our plant, not bad for an electrician/mechanic eh. :laughing:
Build memories, take a kid out doors and teach them about nature by interacting with it, hunting and fishing.
Learn from the past, don't dwell on it.