The dreaded sludge.

[pittzer]

Okay, so my wife drives an '03 QX4 with 60K miles. We bought it with about 35K on it from previous owner. It was a trade-in and we bought it from the Infiniti dealer. We had it checked out and everything seemed to be in good shape.

Just recently the check engine light came on. Our mechanic traces it to a timing chain sensor or cam sensor. Can't remember what he called it, but it basically tells the EFI when to shoot gas into the cylinder and spark. So, yeah it is something that can leave you on the side of the road. Mechanic says timing chain and sensor are covered in sludge. Why don't we change the oil, etc. etc. We protest we do it religiously every 3K miles. I'm sure he doesn't believe us, but whatever.

We have come to the conclusion that the previous owner must not have been so good about it. The mechanic suggests we replace sensor, flush the engine and change the oil. Duh.

Is there anything that can cause oil to break down prematurely? Should we switch to synthetic or a blend after this situation is taken care of? Is my engine doomed?

[Densetsu]

Should be the same with the QX4 as the Pathy: My '03 has this in the owner's manual:

"NISSAN does not recommend synthetic type oils but recommends mineral based oils. These oils must however, meet the API quality and SAE viscosity ratings specified for your vehicle."

Never knew why, but someone on here or another Pathfinder forum suggested the gaskets on the '03 might not be able to handle synthetic. I thought it was werid, especially since the '01 and '02 owners manuals said nothing of the sort.

[Buzzman]

Interesting.I switched to synthetic on my 2002 right after I bought it. It was one year old, with about 40K Kms. on it.I wouldn't switch back at all. I now have almost 190K Kms, and the engine runs strong and clean. Absolutely no oil leaks or usage. I go about 6,000 kms between changes. From everything I've read, the problems begin if you switch back and forth between synthetic and dino. Go with one or the other, and stay with it.Try an engine flush like the tech suggests, and see what happens.Good luck.

[pathfinder9035]

yeah i have been using part sythetic and no leaks nothing engine runs strong. man i really hope thats not true about what nissan is saying about sythetic. now thats just starting to scare me.