I was driving my Loyale today and noticed that I was getting smoke out the back under acceleration. When I got home, I popped the hood and saw smoking grease/oil on the cat that sits right behind the passenger side CV.

There are grease marks where it looks like the CV flung its grease out, but that was there before. I recently had the driver's CV go, and I did a complete half-shaft swap with what is supposed to be shafts with CVs that are better equipped for lifted Subarus. The New CV has grease/oil "drops" on them, the boot looks fine, and there's no evidence that there is new grease being flung from the CV. There is evidence that this fluid is coming from somewhere else and hitting the new half-shaft though.

I would say it looks like grease more than oil, but the stuff on the front cat was oil-like (due to heat).

I do have an oil leak on the engine, but the engine looks dry in that area (the bottom of the engine is wet and I'll get some drips on the ground under the car).

I'm a little mystified by the source of this. 

I am planning an engine/trans swap in the near future, so I'm not worried if it's something significant. I want to get through this winter with the car and not worry. I checked my engine oil level and trans fluid level, and they both seem fine.

Anyone have an idea of what I should investigate here?

I would first try to identify what is hitting the cat and smoking. I've wrapped fresh aluminum foil sheets (no fires) around or near parts like that and then did a short freeway drive to look for early signs of what fluid I'm dealing with. Could there be a pin hole or tiny slit in the CV boot where grease is flinging out but only when under high RPMS so hidden otherwise?

 

I find CV grease can fly out pin holes when things warm up. Hard to find pin holes I know. Also find CV grease is not dissolved by standard degreaser. You need a solvent like wax and grease remover to clean up painted under bonnet surfaces. If you can get at the grease elsewhere where it has not cooked, try degreaser clean up. If that not work it is likely CV grease, try W&G remover. If that works .....

There was a slit in my CV (brand new half-shaft), but it was obviously turned so I couldn't see it. 

Obvious answer, I just assumed that I shouldn't have a torn CV on a new half-shaft.

who put it in ? Sometimes, stuff gets in the way of install that may damage boots, such as the splash guard panel off the chassis. Some tend to bend it out of the way, then bend back when complete. It may have sharp edge ?