Rod knocking, out of oil, or both?

Question

So, I had noticed what sounded like rod knocking in my 2004 Nissan 350z with 140k miles. IT got progressively worse, and I went to look around. I ended up finding all of my oil gone, seemingly due to the infamous Jiffy Lube incompetence at installing oil filters (it fell off with a flick of the finger).

At the suggested of a more mechanically experienced friend, I added 3 quarts of 20w50 conventional oil, and 2 quarts of 85w90 conventional gear oil (after checking there was not reaction to the mixture).

The sound all but disappeared as expected, however, it makes me wonder -- how temporary is this? I had probably driven about 80-160 miles with 1-2 quarts of oil. At the time of drainage (some days after noticing the problem), I got about 1/2-3/4 quarts out, and my collection for the leak had collected another 1/16 quart or so over ~15 hours of measurement. The oil smelled burnt, at 1500 miles (synthetic, high mileage 10w40).

I imagine I should ditch the car ASAP, as I do not have a space to use an engine hoist to rebuild the engine, nor the money to pay a mechanic to do so. Is it possible the rod knocking was only normal due to the lack of oil, or is the engine genuinely trashed? I imagine the latter, but input is appreciated.

Answer 1

There is simply no way to tell, without tearing down the engine and checking all clearances and bearing surfaces.

Adding thicker oil to mask the sound of failed bearing babbiting will not last long. I would drain this voodoo mixture, and add the OEM spec oil. If the noise returns, even slightly, you have deeper issues and must contemplate a rebuild or selling the car.

This engine has solid lifters and fixed cam timing, so any "knocking" noise is likely from the bottom end. It doesn't sound good.

Better Luck!