I used conventional oil in a '99 Mazda B4000 I bought used with 104k miles, changed w/filter every 3000 miles, sold it with 330,000 miles on it and it still ran great. No internal engine issues while I had it. In my '17 RAM, I run Pennzoil Ultra Platinum full synthetic but still change the oil/Mobil 1 filter every 3000 miles. If it works, I stick with it...........