Okay so I really wanna open this can of worms— but for good reason. The 4Runner has 314,595 miles on it as I’m writing this. I’ve ran full synthetic 5W-30 ever since my ownership (bought with 191,586 miles) and nothing else. Use AMSOIL signature series from 200K-273K, then Pennzoil Platinum for two oil changes, then Pennzoil Ultra Platinum from then on until my last oil change, which was at 314K.
As you can tell, I’ve been a bit of an oil snob/purist over the years. Well it all changed recently when I discovered that Costco has their own line of oil— Kirkland Signature full synthetic. It’s made by Warren Distribution, who also produces Walmart’s SuperTech as well as the AmazonBasic’s oil. Figured I’d give it a shot since I’ve been extremely diligent about oil changes over the time I’ve owned the truck. It should be noted that I’ve also ONLY ever ran 5W-30, nothing else.
So recently, I’ve noticed more wetness on and around my oil drain pan. Yesterday I crawled beneath it and wiped everything off that I could see was wet/damp with oil. I’m planning to extensively monitor this over the next few months, checking it daily/weekly/as regular as possible.
My question, after some deep thought and lots of research, is, would you suggest running a full synthetic high mileage oil OR bumping my regular full synthetic up to a 10W-30 offering? Again, 314K on the ODO, all original everything, engine/trans/etc.
I have my personal reservations about running a high mileage oil. I’ve read that they’re a crock of shiz, but have also read that they’re like slapping a bandaid on a larger problem, like leaking rear main seals, etc. I also don’t know where this wetness/dampness of oil is coming from, so that may be my next big investigation.
I’d like to stay with the Kirkland Signature full synthetic as long as I can help it. From my understanding, the HM oils tend to cause seals to swell, resulting in the slowing/stopping of oil leaks. So I’ve got some decisions to make and would love some info/input on the matter.