Oil pooling in top of cylinder head.

[Nilao]

You talking about the dd15? The same dd15 that will ventilate the block if you dont follow the procedure for changing the filters? Or the dd15 with the cheap press fit crank rather than a forged crank? Maybe your talking about the old series 60 which shouldn't be compared with the isx as they're fundamentally different technologies.

Now CAT. You say reliable..so you can't be talking about the BXS model that nearly bankrupted O/O that had them. Then you had the MXS/NXS that had issues with the VVA technology. Then the whole regen system fiasco that finally took CAT out of the on highway market.

The series 60, 3406E, and N14 were the last of the easily repairable, throw any part at it and it will still run engines made.

Our of the big 2 on highway manufacturers the cummins is the easiest and most forgiving of the 2
I have owned all 3. I miss the CAT reliability but not the fuel consumption. I hated the 1 box design of the dd15 and its finicky lubrication system. The isx 870 and 871 are the perfect mesh of new computer technology and old mechanical components. The 2250, 2350, and x15 I cant comment on as I've never owned one.