4.0L mileage survival??

champ · 06-15-2023, 04:45 PM

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.

06-15-2023, 04:45 PM	#8
champ not cool enough Join Date: Nov 2006 Location: IA Posts: 2,612	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.