Engine braking and oil consumption

SoCal LS-L · #1 05-06-2010, 09:50 PM

Heres a question that has been on my mind for a bit, as I still routinely drive up and down the Mt Rose pass at over 9000 feet.

I have noticed that my car loses oil at a much faster rate when I drive this mountain road..... and I do not ride the engine in high RPM's while climbing. My car does not burn oil on regular freeway trips either. The only thing I can think of is my tendency to keep it in "3" whilst coasting down either side of the mountain. I do not like to ride on my brakes and the SVX has a tendency to want to get into triple digits during downhill grades in Drive.

The difference in oil consumption between flat land travel and mountain runs is massive.... should I be concerned that my valve seals are shot... or do you think that the problem may be more benign.... such as a PCV issue? Has anyone else noticed excessive oil loss due to long duration engine braking?

The Reno side of Mt Rose is about a 25 minute long coast down a steep winding grade, and I usually let the engine handle most of it. Im not that familiar with the characteristics of HO engines..... should i just leave it to the brakes?

K_Dub · #2 05-06-2010, 10:10 PM

Interesting question. I too use engine braking on a daily basis for a 2k ft drop from my house to the beach. As such, I don't have a flat-land comparison available, but I don't believe I'm burning any more than usual. I will say that I've always used engine braking on my previous Subarus (all MT equipped) and never experienced your problem.

I'm curious to hear what others think about this hypothesis.

sperry · #3 05-07-2010, 12:46 PM

You might have a good idea with your PCV comment. The PCV opens to vent the crank when you're under lots of vacuum. And what generates vacuum? Engine braking.

If your PCV is eating oil, a long coast down from Rose will certainly accelerate the issue when compared to driving on the freeway under throttle. I don't know if simply replacing the PCV will address this, but it can't hurt to try.

Actually it probably will hurt to try... it will hurt your knuckles, because it's a ***** to get a wrench on that PCV to replace it. I think you pretty much have to bend a wrench into a custom tool to do it. I've had a spare PCV in my toolbox for like 3 years now, and have yet to get around to swapping it because it's so hard to get to.

SoCal LS-L · #4 05-07-2010, 01:16 PM

Quote:

Originally Posted by sperry

You might have a good idea with your PCV comment. The PCV opens to vent the crank when you're under lots of vacuum. And what generates vacuum? Engine braking.

If your PCV is eating oil, a long coast down from Rose will certainly accelerate the issue when compared to driving on the freeway under throttle. I don't know if simply replacing the PCV will address this, but it can't hurt to try.

Actually it probably will hurt to try... it will hurt your knuckles, because it's a ***** to get a wrench on that PCV to replace it. I think you pretty much have to bend a wrench into a custom tool to do it. I've had a spare PCV in my toolbox for like 3 years now, and have yet to get around to swapping it because it's so hard to get to.

Its funny you say that, because I have one too that has been in my center console for a year now. The hose that connects to it is rock hard from age so Im skuurd to try to pop it off and break it, making a giant vacuum leak until I pull the whole manifold. No thanks lol

Mike621 · #5 05-08-2010, 01:08 PM

Quote:

Originally Posted by SoCal LS-L

Its funny you say that, because I have one too that has been in my center console for a year now. The hose that connects to it is rock hard from age so Im skuurd to try to pop it off and break it, making a giant vacuum leak until I pull the whole manifold. No thanks lol

You can replace the PCV hoses (both) for bout $20 new from Subaru. I actually have one of the two new in package for $8 shipped if you wanted it.

wdb · #6 06-19-2010, 10:42 AM

Quote:

Originally Posted by sperry

I've had a spare PCV in my toolbox for like 3 years now, and have yet to get around to swapping it because it's so hard to get to.

Can you tell me what it looks like or what part number is on it? I got one from SubaruPartsForYou.com, supposedly fits all SVX 92-97, and it is not the right thing. Threaded end is too big, hose end is too small. The one on my intake manifold is larger on the hose end than it is on the thread end, and the one they sent me is the opposite.

The part number on the bag is 11810AA100 (that's the wrong one).