Purpose of Underbody Plastic Shields?

[Dechion]

I was reading in another thread about changing the oil involving removing underbody covers, which plug gasket to use, etc.

I didn't want to derail that conversation, but was wondering about the covers themselves.

I know on the FX4 there are skid plates that protect vital components from damage. That makes perfect sense. People have been putting armor on things they want to protect since the middle ages (and probably before).

What I am more curious about are the plastic panels underneath most modern vehicles. I know they wouldn't be there if they didn't serve a purpose. I am just wondering what purpose that is.

They don't seem to be very strong, at least on the Kia I'm driving now. Most of those panels have broken and are now gone. Was planning to replace them as that happened, but noticed no adverse effects on the car so I never got around to it.

Would it make sense to just make an access hole/panel/door to access the filter and drain plug? Seems like that would be easier than taking the whole panel off every time.

The only reasons I can think of for having them in the first place is to either help keep the engine warm during operation or to lower underbody wind resistance to increase fuel economy at high speeds.

Something tells me I'm overthinking the hell out of this, lol.

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[ShadowChas]

Yes they wouldn’t spend any extra money for things that aren’t needed - fuel economy is usually the reason in most cases and some companies do put access holes/cover plates for maintenance (wish they all did) after time you see a lot of them hanging down because the fasteners are in need of replacement

 

[Decayed]

Aerodynamics.

 

[jeffrol48197]

They also provide protection from corrosion in salt states like Michigan, especially in the engine compartment area, which has a TON of wiring harnesses, especially on vehicles like my hybrid.

 

[Maverickman74]

Ironically fuel economy is the main reason. I say that because plastic is oil. So they put a product made from parts of the oil they dont use for fuel on the bottom of a vehicle to keep it from using more fuel. Of course as you said about your Kia most of them break and end up on roadsides across the country. Plastic is a horrible material and at most should be limited to recycled materials. Cracks me up seeing a hybrid car covered in plastic

 

[wb5oxq]

Mine is not plastic rather some kind of fiber board.

 

[TwoTone]

Most do have access holes for filter and plug, but if you don't take the shield off, you aren't going to see much and you should be doing an inspection every oil change.

 

[Motorjunkie]

I was reading in another thread about changing the oil involving removing underbody covers, which plug gasket to use, etc.

I didn't want to derail that conversation, but was wondering about the covers themselves.

I know on the FX4 there are skid plates that protect vital components from damage. That makes perfect sense. People have been putting armor on things they want to protect since the middle ages (and probably before).

What I am more curious about are the plastic panels underneath most modern vehicles. I know they wouldn't be there if they didn't serve a purpose. I am just wondering what purpose that is.

They don't seem to be very strong, at least on the Kia I'm driving now. Most of those panels have broken and are now gone. Was planning to replace them as that happened, but noticed no adverse effects on the car so I never got around to it.

Would it make sense to just make an access hole/panel/door to access the filter and drain plug? Seems like that would be easier than taking the whole panel off every time.

The only reasons I can think of for having them in the first place is to either help keep the engine warm during operation or to lower underbody wind resistance to increase fuel economy at high speeds.

Something tells me I'm overthinking the hell out of this, lol.

The one under the engine helps with routing of air through the radiator and a/c condenser in order to maximize their efficiency. The rest are for aerodynamics.

 

[Master Blaster]

Toy are correct in that its all about aerodynamics and gas mileage. The felt one under the engine is probably worth about 1mpg. It also has a side-effect of keeping the engine and the electrical components relatively clean. Its a pain when you do an oilchange, but its worth it. Sooner or later, gas is going to double in price and you'll wish you had more of these aerodynamic aids.

 

[retired242]

something to curse at when doing an oil change after all if it was easy everyone would change their own oil

 

[Superg0]

I had what I called the oil diaper on my F-150. When Jiffylube overtightened my drainplug which is plastic, it cracked it and oil leaked. I called it the oil diaper because for awhile it soaked up a lot of oil, but like any other diaper once it full it leaks. The oil diaper on my F-150 was like carboard covered with a rug on both sides. Not solid like metal or plastic, but fibrous and pliable. Well after the second time they cracked my oil plug my diaper could no longer stay up, and sagged until it was only held on by two clips. Asked JiffyGuber to replace it, they wouldn't. This diaper I am led to believe was a form of insulation to keep heat around the tranny, and act like a deflector.

To answer your question, JiffyLube bad

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