Interesting MPG Gain From Plastic Skid Plate

[CMB430]

Hello,

I wanted to share something I find amazing. I know that air resistance is a huge MPG killer. But I did not realize that the undercarriage had such a large impact on mileage. I took off my plastic OEM belly pan in the fall when I installed the DieselGeek skid plate. It was off for months. I noticed a drop in mileage, roughly 2.5 to 3 MPGs. So I re-installed it when I did the 40K service. My mileage came back up. Instead of averaging 40 to 42 MPGs driving the same roads at the same time of day from the same fuel stop, I am getting 43 to 46 again. That is the only thing that changed to affect drag as I did no performance mods.

I was bored and felt like sharing. This mileage has been consistent since I reinstalled it. I am happy to get more pennies per mile with diesel prices going up.

 

[nutdriver]

I noticed a similar change on my 2000 NB. In my case the change was apparent in the winter but not the summer. The cover had been of all summer and fall. I did not notice the decreased mileage until Winter when my mpgs went down more than expected. I put the cover back on and the mileage returned to normal. At the time I attributed the change to the engine heating up more quickly when it was better isolated by the engine cover.

 

[740GLE]

temps and warm up times durring the dead of winter might also play a bigger roll. Either way, is there any reason not to have the OEM pan on?

 

[James & Son]

Hello,

I wanted to share something I find amazing. I know that air resistance is a huge MPG killer. But I did not realize that the undercarriage had such a large impact on mileage. I took off my plastic OEM belly pan in the fall when I installed the DieselGeek skid plate. It was off for months. I noticed a drop in mileage, roughly 2.5 to 3 MPGs. So I re-installed it when I did the 40K service. My mileage came back up. Instead of averaging 40 to 42 MPGs driving the same roads at the same time of day from the same fuel stop, I am getting 43 to 46 again. That is the only thing that changed to affect drag as I did no performance mods.

I was bored and felt like sharing. This mileage has been consistent since I reinstalled it. I am happy to get more pennies per mile with diesel prices going up.

I thought the diesel geek skid plate went over the plastic belly pan? Can you explain. My car has the spare wheel, under cover, removed due to a trailer hitch install and I bet it is causing some losses. Whats also interesting is the air flow ducts to the front wheel wells as well. Look like Indy hood scoops.

 

[Abacus]

I have run with and without the plastic belly pan, and with and without the Evo skid plate. Saw no difference in mileage with any of them.

 

[1998993C2S]

Yeap, not surprising that a clean, aerodynamically speaking, under side of our TDI's chassis is good for a MPG assist. I too have disrupted the TDI's under side when installing the Curt trailer hitch allthough an effort was made to re-install the trunk area under panel needed to be removed during the hitch install. Hey,,, I'm in the TDI for the MPG's...
Thanks for the post...every detail helps the MPG game.

The under side of my 911 coupe is entirely unobstructed, absolutely flat...

 

[tdiatlast]

I thought the diesel geek skid plate went over the plastic belly pan?

Yes...please explain...Did you swap the plastic for the DG plate, and your MPG went up?

I would think your mileage would IMPROVE with the DG skidplate.

Is the MPG improvement temp/seasonal fuel related?

 

[BritD059]

Yes...please explain...Did you swap the plastic for the DG plate, and your MPG went up?

I would think your mileage would IMPROVE with the DG skidplate.

Is the MPG improvement temp/seasonal fuel related?

DG skid replaces stock plastic skid. you can use the plastic engine side covers with the DG plate with some slight modification if they are not broken. If they are broken it is recommended you purchase DGs Full Metal Jacket which includes aluminum skid plate and aluminum side engine covers.
My OEM skid plate was broke on the side and rear so whenever i encountered a small bump the skid plate would scrape the ground. Im sure that wasnt great for mpgs, however switched everything out to DGs havent noticed a change in MPGs, but i never ran without a skidplate either

 

[tdiatlast]

DG recommended I keep the stock plastic skid plate installed...Maybe it's different between the '06 and the '09?

 

[n1das]

temps and warm up times durring the dead of winter might also play a bigger roll. Either way, is there any reason not to have the OEM pan on?

YES. Replace it with an aftermarket steel or aluminum skidplate or OEM steel skidplate. The OEM plastic belly pan is a POS and provides no protection against road debris if you happen to hit something you can't avoid. It is NOT a skidplate at all. It doesn't take much of a hit from road debris to hole an oil pan.

I have the Dieselgeek Panzer plate on my 2005 PD JWagen and have an OEM VW steel plate on my 2010 JSW. I was glad to get rid of the POS plastic belly pan on both cars. No differences in MPGs were noted when I made the change on each.

On the A5/A6 cars (2005.5-2011), I like how the plate is a simple and flat shape as the engine and everything sits a little bit higher up relative to the car body. On the A4s (1999.5-2005) the belly pan or plate has to make a bend to get under the oil pan and tranny. This is where the A4s sit lower to the ground and are vulnerable to damage from road debris.

I say get rid of the POS plastic belly pan and install an aftermarket metal skidplate or go with the OEM VW steel skidplate as cheap insurance against damage.

 

[Dieselgeek]

Hey y'all,

I just wanted to clear some stuff up:

The MK5/MK6 Dieselgeek Panzer Plate was designed to sit directly below the stock plastic belly pan. If you take off your MK5/MK6 belly pan and then install the Panzer Plate then there will be openings on the sides where water and dirt can get in and very valuable, efficiency boosting heat can get escape. The plastic belly pan is highly beneficial when used with the MK5/MK6 Panzer plate. I designed the Panzer to be as small as possible to provide great protection without adding unnecessary extra weight while retaining all that is good about the factory plastic belly pan.

Any assertions about mileage changes like the OP states are in my opinion questionable from a scientific method standpoint when seasonal fuel and ambient temperature changes are considered. The profile of the Panzer Plate is exactly the same the OE belly pan by design. It also follows the belly pan very closely and the frontal area is very small, maybe 1-2 inches tall.

 

[CMB430]

If anyone is interested, I would be happy to take some time and post out numbers, dates and fuel ups. There has not been a change in fuel grade for over 90% of the time before and after the reinstall of the OEM plate. I am only public school educated, but I do know how to count and do simple math with a TI-89 .

In SEP10 I removed the OEM plate and installed the DG one. During my last service (see my long post) I put it back on UNDER the DG plate; meaning both are in place. It may have to do with engine warming...that is very possible. But it also keeps a majority of under car air from the left and right sides of the engine compartment. I have OEM fog lights on the car with the matching grill inserts that are open so air enters that way. Like I said, I did not change anything physical on the car (besides filters) during the service so I have little to doubt that the OEM plate has increased my mileage back to where I was prior to removing it. Keep in mind that when I removed it in SEP, I put over 3,600 miles on it over 2 weeks on a long road trip.

 

[tdiatlast]

Under? Over? Is the OEM belly pan between the DG plate and the engine?

If so, than you are in fact proving what Jim said...you've enclosed the voids on the sides, and the engine is staying warmer...also maybe cutting down on undercarriage turbulence?

 

[CMB430]

Correct. DG plate, OEM plate then engine. I just know that gallons in vs miles driven vs gallons in hand calculated from the same gas station most of the time is pretty accurate.

I am sure glad the tornado did not touch down tonight they were warning us about.

 

[nhdoc]

Let's see, he took the belly pan off just before winter fuel hit the market and the weather turned cool and his mileage dropped, then he put it back on just as temps begin to warm up and the mileage goes up again...cause and effect, of course, the belly pan causes the climate to change!

It's about as probable as it being responsible for a 2-3 MPG drop in fuel economy...in other words, no, the belly pan isn't responsible for the change in mileage - it's those other factors. If you don't believe me take it off again and drive through the summer without it and see.