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So, why do they put this plastic pan under the engine bay? Makes it kind of hard to inspect the undercarriage. I heard it was for improved fuel mileage.

My 2008 Mazda 5 2.3L has this shield. It also has an oil cooler. My 2001 Ranger had the 2.3L, no shield, and no oil cooler. Could it be that the oil cooler was added because the shield resulted in higher temperatures in the engine compartment?

What happens if I remove the shield and remove the oil cooler?

i always pictured it as protecting things, without ever really thinking about it, but the mpg thing sounds like a better reason. i've heard of people taking that covering off, along with heat shields under exhaust piping etc., but never removing oil coolers. maybe rope will chime in?

As my oil cooler housing is leaking, it will need to be replaced. That is a good time I should convert to the spin on filter. Up is to the left.

Number one reason for a Belly-Pan is to reduce aerodynamic drag.

Yes, Belly-Pans may result in higher under-hood temperatures and oil coolers might need to be added to mitigate this concern.

"To improve Cd, designers may make the following changes:

Round the edges of the front end
Tune the grille and fascia openings
Tune the wheel openings
Place spats (small spoilers) in front of the tires to reduce turbulence
Tune the size and shape of the outside mirrors and their attachment arms
Reshape the water channel on the A-pillars
Adjust the front fascia and air dam to reduce drag under the vehicle
Add side skirts
Tune the deck height, length and edge radius
Install a rear spoiler
Adjust the angle of the rear window
Tuck up the exhaust system
Use a diffuser to tune air coming off the underside
Install "belly pans," underbody panels that cover components and smooth airflow"

https://www.edmunds.com/fuel-economy/im ... onomy.html

You'll also see Active Grill Shutters on some vehicles, so underhood airflow is minimized unless engine cooling needs demand more airflow.


"A wonderful bird is the pelican,
His bill will hold more than his belican,
He can take in his beak
Enough food for a week
But I'm damned if I see how the helican!"
- Dixon Lanier Merritt

Even without the pan that's a tighter engine compartment than a Ranger. I definitely would not assume removing the pan would add enough airflow to warrant removing any coolers. It might even be counterproductive depending on how carefully the intended airflow path was tuned.

From my recollection, the ranger was tight, but this Mazda 5 is not bad. There is a lot of room between the engine and the firewall. It really does looks like a spacious engine bay by today's standards. I find that if a V6 will fit, the 4 banger ought to have some extra space around it.

Anyway, ClutchDisk took the plastic pan off his 2009 Mazda 5 and is getting excellent mileage (around 34 mpg last tank) and no issues with heat. He also has the 2.3. Actually I am the one who removed his pan, at his request.

Just removed the pan from wifes 2008 Mazda 5 and found the tranny pan was pretty rusty. Would not have known with the shield in place. So in some respects the shield can cause problems by obscuring visibility of engine components.

Both my and ClutchDisk's shields were partly zip tied on. One thing for sure, with the shield removed I won't have it come loose and jam up under the car while driving.