Ive seen youtube videos with lawnmower that run with SAND in the crank case. LOL!!!
As long as the oil is not heavily contaminated with water, fuel, dirt or other, the mower will run fine. May folks like HDEO oils in particular 15W40 for outside engines as a replacement for SAE30.
My 24HP V-twin briggs and stratton get Penzoil Platinum 5W30 because thats what I use in my truck. I do run a car oil filter on it (motorcraft) which has much higher capacity than the stubby brigs and straton. been in the engine for two seasons and still looks good. Everytime I setup to drain it, it looks like most oils look like coming from the bottle.
Just cant do it.
Once the filter starts rusting maybe i will.