I routinely serviced a 98 XJ, starting around 250K, and the 4.0 finally gave up the ghost around 410K.
The owner had top end ticking starting around 320K along with low oil pressure (5-10psi hot idle). Switched out to 15W-40 from his usual 10W-30 and ran it until it lost all compression on #1 at 380K. He kept it going on all 5 until it windowed the block at 410K.
So yeah... heavier weight oil and send it.
|