Rural king (farmers fleet) motor oil.
Even so there isnt an oil company out there that's gonna warranty a 20 year old truck with 289k miles
They aren't going to warranty your truck, but they will warranty their product. If the oil fails to do what an oil is supposed to, and you suffer damage to your engine because of it, you will have a legitimate warranty claim. That will always require an oil analysis, which will reveal what caused the oil to fail, if it indeed did. It will also reveal if an additive was used.
Here's what Lucas Oil Stabilizer is, and what it does.
It is a thick, Group I (low grade) oil, with virtually no additive. That's it.
It will considerably thicken your oil, and dilute the additive package, reducing the useful life of your oil. The higher concentration of Lucas used, the greater the effect.
If you want thicker oil, just buy one, and you'll have the full, undiluted additive package. I'd only use the Lucas in a worn out engine on it's last leg, that had knocking or oil burning problems. Back in the day, I used STP in 351 Cleveland that knocked a bit on startup.
Hopefully this has been informative to you.
