I think that maintenance is sufficient if the vehicle is driven regularly and not short tripped. Also, if the engine is easy on the oil compared to a turbo charged 4 banger with fuel dilution.In the last 10 years I have looked at perhaps 30 used cars. I check them out for myself and when my kids need a new [used] car. I look under the oil cap to see some part of the cams/head. All the cars have been remarkably clean and shiny inside. Invariably when I ask about oil changes they answer they just take it to the local oil change shop every 5.000 miles or so. This would be just bulk oil, synthetic or conventional. So in my experience this cheap oil does a good job at regular intervals. I haven't seen a car with dirty engine internals in 20 years or more. Maybe I'm just lucky.