If your RV is a diesel pusher like ours, and you sometimes find small specks of oil on the front of your toad (towed car), there’s a little black tube under the engine that just might be the source. It’s a part of the crankcase ventilation system commonly known as the breather tube (some mechanics call it the “slobber tube” instead). You’ll see why here.

The purpose of the breather tube is to allow excess combustion gases to escape from the engine. But if your oil is overfilled, some of it can get into the breather tube as well, causing it to spray out behind your RV as you drive down the road… and onto your car.

The most obvious solution is to avoid overfilling your crankcase, but unless you change your own oil, you might not have total control over that. Whenever possible, we generally try to keep our oil level about halfway between the full and add lines on the dipstick.

Another tip requires an empty plastic bottle. Make sure to use the heavy-duty plastic type from something like an iced tea as opposed to one of those flimsy, super thin water bottles. In addition to a strong plastic bottle, you’ll also need a standard zip tie.

Using a razor knife, cut off the top off the bottle. You want to open it up wide enough for the breather tube to fit, plus a little extra. Again using your razor knife, make a small slit near the top of the bottle. Then slide your zip tie about half-way into the slit. Now it’s ready to install.

Simply slide the bottle over the end of the breather tube and zip tie it loosely to an existing clamp or fitting. Then just clip the end off the zip tie and you’re good to go, catching any blow-by before it splatters onto your car. An added bonus is the ability to see how much oil is blowing out of your breather tube by looking at the bottle from time to time. If you’re seeing a lot, try keeping your oil level a little bit lower.

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  1. Great Idea,,,one question: does the heat from pavement or engine cause damage to the bottle which would require the bottle to be replace?

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We're handy RVers, not professional technicians. We're happy with the techniques and products we use, but be sure to confirm that all methods and materials you use are compatible with your equipment and abilities. Regardless of what we recommend, consult a professional if you're unsure about working on your RV. Any task you perform or product you purchase based on any information we provide is strictly at your own risk.

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