changed the oil on my 3.0 Ranger today, I've used mostly Fram filters ranging from the Extra Guard to the Ultra. The oil filter is in close proximity to the driver side exhaust manifold and cat, so it must be exposed to a good bit of heat. Upon removing the Tough Guard filter, I noticed that most of the coating was very bubbly. It was not bubbly at all when I installed the filter 4k miles ago. I did run the truck a bit harder this oci, shifting high into the rev range most of the time, which will obviously generate excess heat. I'm assuming its nothing other than the heat from the exhaust that caused this, but could it possibly be something else? The paint and metal on the can seemed fine, just the coating was bubbly.
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