The XW/HTHS grade measurement is on the right track but perhaps not precise enough.Right. Shannow invented the XW/HTHS grade. Pick your winter grade and desired HTHS. All that is in between, is not important.
Each oil range (ex: 5W-30) has a wide viscosity range (ex: [email protected] and HTHS range) that it allows, so if you happen to get a thin 5W-30, it might be about the same as a thick 5W-20.
I like to choose thick 5W-30's that are approaching the upper limits of thickness in the 5W-30 viscosity range spectrum,
so you can get the full benefits of a higher HTHS and high MOFT.
Personally, I also like to use high mileage oil, only because I like that it treats all the oil seals in the engine to keep them at the soft original
size they were when they were new, to prevent external oil leaks on your driveway or garage floor. It also stops internal oil leaks which can reduce oil burning.
I buy all my oil in 5 quart jugs from Walmart, and all my filters from Walmart or Amazon, and then just pay $14 labor for my local tire shop to do the oil change. I try to avoid going to places that use the cheapest bulk oil and the $2 oil filters and then pad their profit by charging you $40 to $50 for the oil change. They are not a really good value for the consumer in my opinion.