I remember back in the 70s and 80s some motor oils left behind heavy deposits of hard sludge and stuff. Quakerstate oil was notoriously bad, and you had to take that into consideration if you were buy a used vehicle. I’d pull the PCV hoses off for inspection, and use my sniffer on the oil and transmission dipstick.
We used Pennzoil in the shop. As I said I was influenced by NASCAR sponsorship as a vehicle owner so I developed a taste for Havoline or Valvoline. Mark Martin and Ernie Irvan were my favorites! grin
Nowadays I’ll buy a five quart jug for oil changes and keep a couple single quarts handy in case something starts to run low. Her damn Subaru Crosstrek is the only thing I usually have to add to.
She’s had three Subaru 4wd SUVs. The first two were Forresters, and both went over 200,000 miles. This one is a ‘14 with 40 k on it . I strongly suspect it’s the last Subaru she buys as well.
7mm

"Preserving the Constitution, fighting off the nibblers and chippers, even nibblers and chippers with good intentions, was once regarded by conservatives as the first duty of the citizen. It still is." � Wesley Pruden