I've been tracking down a number of low grade oil smells in the car lately (2004 Subaru WRX). So far, that has included replacing the left front axle (was losing all kinds of grease through the boot), replacing a power steering hose that had a tiny hole and fixing a slight overfill of transmission oil.

However, I still have a slight hot oil smell after driving home from work. After a little bit of under hood detective work, I see this:

Oil on the throttle body hose

That's the throttle body hose coming out of the front side of the intercooler. This is not a place that I would expect to find oil. For context, here's a larger scale picture:

The same hose with a little more context.

So the question is: what is going on here? How did oil get on top of that hose (and on the edge of the intercooler)?

  • What are the pipes below or right next to the inter cooler? Are those the power steering pipes?
    – kasey
    Mar 3, 2016 at 20:15
  • @kasey when I had an 03 I recall they were the vacuum lines. Could be wrong. Mar 19, 2016 at 19:56
  • Have you had to replace your turbo for oil consumption? Mar 25, 2016 at 15:21
  • Nope, turbo is still boosting fine. Oil consumption is higher than a non-turbo but within expected parameters.
    – Bob Cross
    Mar 25, 2016 at 20:07
  • Did you find the source of the leak? Apr 9, 2016 at 17:21

3 Answers 3


I'll start off by saying that this may not be an answer, but rather a methodology for diagnosis. On that Subaru, the turbo should be to the right hand side of the engine. You have oil pick up and return lines for the turbo. By design the serpentine belt can swing oil up onto the ceiling of the hood if they leak. The easiest way to troubleshoot this issue would be to clean the engine bay as much as possible. Once clean, apply this dye


It doesn't have to be that brand, but I've found when phantom oil leaks occur; This is a life saver. The problem with troubleshooting oil leaks is that they make a huge mess and it's impossible to actually determine where the oil is leaking from. I usually wait until it's dark, get a black light and let the car run. Once the leak occurs it's very obvious. I hope this was a little helpful!


Could be a small hole or crack in your inter cooler that is letting out oil that has leaked out of your turbo.

Or possibly the inter cooler to throttle body joint is leaking the same oil.

I have seen this on a different make/model car.


Much much later, I finally took things apart and found the real cause: the PCV pipes that run next to the intercooler. It turns out that I had somehow developed several pinhole leaks all down the pipe, each less than a millimeter in diameter. It's not clear what caused these leaks to form but, after replacing the PCV pipe, oil mess is not forming and the smell is effectively gone.

You'd think I would have checked that first but I'm often convinced than I'm smarter than I am.... ;-)

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