At 167,000 miles, I run my 1993 3.0L with Mobil One 5-30 Synthetic for High Mileage Vehicles. The prior owner used a different brand but also 5-30 Synthetic High Mileage. I tried running conventional 5-30 with 20% Lucas, but found the engine did not like it (more start-up tapping from the lash adjusters). Also use OEM filters.

1993 Montero SR 4dr V-6 3.0L Auto "Thunder" (in Alaska)
1960 Bentley S2 V-8 6.3L Right Hand Drive