Massive Drag Reduction For Tiny Budget - How I turned my family car into an AERO Star

A 25% reduction in highway fuel consumption is impressive. Even more given the car looks so stock still.

I mean, with the lowering springs, moon discs, white walls and roof rail delete it got a simple yet unique vibe

The car actually looks really good, like the concept sketches they do when creating designs.

Your car looks like a futuristic concept car from the early 2000s, and I love it. It reminds me of my childhood days when I would spend hours staring at concept car photos.

I am very surprised with how large of an efficiency gain you had! Great work. Have you done this to your current daily driver?

Great stuff. I did a similar project a few years ago with a Polo 1.2 TDi. Got it basically for scrap money so hadn't anything to lose really. I stripped a lot of weight out as well. Was able to push over 100mpg out of it

The content level is pleasing and precise. Clear data and both including metric and imperial units. Bravo.

Loving this. I've got a Touran converted to electric where low drag is even more important. The exhaust duct and air intakes are already closed off because we barely generate any heat at all. But that is only 2 of your 15 measures completed. Thanks for the inspiration!

About 20 years ago I did a similar experiment on my historic race car. I removed the wing mirrors and wipers, taped up the front panels and part of the front grille. It certainly helped reduce the lap time.
The idea of using foam between the panels sounds very good and better than using "helicopter tape" which left a mess to polish out.

The 1.9TDI PDE is always remarkable in its fuel economy. A relative of mine has a 131hp 6 speed 1.9 in a Sharan, which is the biggest actual "car" you could get, maybe the Caddy Maxi is longer yes. But above that was the busses / transporter vehicles you could say. Well back to the story, despite being a very high and a moderatly long car with a huge windscreen, it is driven without every thinking about it, with 6,5l/100km. If you drive constantly with a little effort then 5,X is no problem. I drove it once and got 4,3l/100km on a 80km trip, 20km country road, 5km city, 55km Autobahn. But I also only drove 90-105km/h, much less than you with 130. Still for such a big car, I am always surprised, and it is not even really slow, the 1.9TDI has a lot of torgue until 2500rpm. VW was a very early adopter of offering 6 speed gearboxes even in cheaper cars and smaller engines, not just in sports cars.

Even though I would not go this far on my cars it's nice to get some inspiration and see how much the modifications improve aerodynamics.

First hot glue mention I obviously have to be: "oh well armchair this and that... Temporary at best... No good"
Later on: "and then I just sat the rack back on and all the holes in the roof opened as if divinity"
I actually stood and applauded. Bravo.

This is the exact reason why I bought my Ibiza 1.2 TDI Ecomotive. It comes stock with high gearing, aero mods, skinny tyres and an very efficient 3-cyl engine. Perfect starting point for further mods.

Martin, please keep doing what you’re doing. Love your videos!

I’ve seen videos doing this, but seeing someone more qualified is a lot more intriguing.

Would be nice if you had measured change in efficiency with each individual mod. Still pretty cool to see efficiency mods like this, and thanks for not making the video longer than necessary

Interesting. I've thought about doing something similar, but didn't think it'd be worth the effort. 20+% improvements definitely seems worth it, thanks for this.

It is more important that the average cars , that accounts for millions of real world km, uses 1L less than to design an absolute record prototype car. So , your experiment has much value in the real world. Well done 👍

The Passat Variant already had a good (for 2006) drag coefficient of I think 0.29 or 0.3 (there was a Bluemotion version that even lowered this by 10% or so). Your modifications go even further and you may have been in the 0.25 range, possibly even lower. My current car, an 150HP TDI Arteon Shooting Brake, which is at 0.26, uses around 5.5-5.8l/100km with a not insignificant city driving ratio. I can easily dip it below 5l /100km, depending on the route and traffic. I find that quite impressive, considering this car is physically larger, weighs 1700 kg, has fat tires (235/18s), all modern creature comforts, safety features and is loaded with tech.

Very thorough explanation, and a good do-it-yourself project. I would like to have seen your fuel mileage after you repaired/serviced the engine, but before your aero mods. Cheers from Canada.

Thanks for sharing your insights. Apart from their function I like the aesthetics of the moon discs.

Excellent work! Very thoroughly and thoughtfully done! I know the exercise here is only aerodynamic improvements fit for your use case with a stock drivetrain but I would have been interested in additional modifications such as optimizing top transmission gear to sit at the most efficient RPM when at 80mph or other mechanical improvements and trade-offs.

I do love seeing a difference from modifying a vehicle, i have a mk2 mr2 and fitted an aero cover over the engine bay flush with the buttresses either side. Originally it was purely for the cool lovre asthetics but it definitely improved motorway mpg too, win win

So much stuff that a layman like me wouldn’t think of! And interesting to hear your process.

Engineering at its best!
Absolut genial was du da gemacht hast! Ich wäre extrem interessiert an einem leichten, minimalistischen, schwach motorisierten Kombi der auf Effizienz getrimmt ist.
Ein Freund von mir hatte einen Renault Megane BJ 2015, 1.5dci mit 6 Gang HSG .
Wenn man den sparsam fuhr (Tempo 90-100 auf der Autobahn) merkt man dass das Kühlwasser nicht auf Temperatur kam. Wir vermuteten immer dass das Auto mit dem selben Kühlpaket wie der 1.9dci ausgestattet wurde.
Trotz lausiger aerodynamik konnte man den Megane problemlos mit 3.6l pro 100km fahren.
Im Alltag mit Tempo 120-130 lag der Verbrauch immernoch bei respektablen 4,3l pro 100km.

hello nice project!
can you consider:
1) close rear arches to have like citroen wheel covered?
2) some front wheel arches spoilers to direct air away of the rear part of them to make smooth air flow in the side of the car like in Saudi a6? (front bumper in the corner have some additional spoiler to make vortex to avoid air come in to front wing wheel hole?
3) rear splitter to direct the air far away the car to don't suck (underrpressure) suck car back like usually all combi/wagon have?
4) some small winglet to make smaller drag for the mirrors?
5) suspension spoilers if they not hide underneath?
6) rear door (trunk) longer spoiler to extend gradually roof?
7) tires from electric vehicle?
8) wheels from magnesium to have less mass?
9) do you play a little with camber and other suspension tweeks to make it better for efficiency then handling in corners to have flat wheel going straight? (wheel alignment)
10) do you think about exchange fuel and air filters from more restricted ones to more open ones?
11) do you think how to play with EGR to have better fuel efficiency?
12) do you think about changing engine oil for less resistant one (0W20/0W30)?
13) do you think about small over pressure on tires?
14) do you think about front covers on the bumper to close this mesh thing (3d print?) like some people use accessories one for winter?
15) do you think about use some magic PPF to close the gap permanently between body panels only without doors and bonnet?
16) do you think about changing alternator for smaller one, change all bulbs for certified led ones include dash board, interior, exterior?
17) also I will think aboutsome new ECU and tune some 3-4 maps to have better power in the low rpm, or some different parameters on some eco mode I know TDI 1.9 not everything you can regulate but this one will improve a lot. 18) also with this you can exchange wheel bearings for new one
19) exchange turbo for new one (this save quite fuel)
20) exchange accumulator for lition BMS alternative one (lighter)
I think you can go down up to 2,7-3,5 in hi way

Another thing you could do if you are good with any bondo or other body work materials is cover the unused vents to create a smooth surface this would further reduce drag you could even install a small diffuser that will increase some down force but should also create less drag if you want to goto the extreme remove the door handles and once again smooth it out with something else just maybe have a latch underneath to get in next you could have vents coming from above or on the side next to wheel well to reduce the air tumble caused from the tire and extract it out the side further reducing drag and adding some cooling another thing you could do is add a vent somewhere along the hood to reduce the pressure and heat under the hood

Years ago I did a fair amount of sealing around the radiator combo of a Volvo C30 for the same reasons you give here. Removed everything before selling the car too. I did some tufting on the rear hatch but decided that any modifications there would be too eye catching. I had experimented with tufting before on a glider's wing, to help with turbulator strip placement :)

01:37 For those wondering, that is the Ingolstadt plant of Audi.

Tolles Video! Wäre unheimlich spannend zu wissen wie viel einzelne Veränderungen ausmachen. Die Felgen und die Tieferlegung alleine dürften schon grosse Veränderungen mit sich bringen.

this is the sort of modification im into. something cheap and practical that won't drastically change the car from its stock specs.

It would be amazing if you could make tests like - fuel consumption with moon disks, fuel consumption with foam, fuel consumption with lower springs, fuel consumption with new tires, fuel consumption with plates under the car... etc
We would have a hint with what we should begin with :)
I have a Honda Fit/Jazz from 2003 and I would love to make some improvements...

Love the video - great job man.
Thank you for the time and effort.

Stark durchdacht
und das Optimum an Effizienz rausgeholt
Tolles Video 👍🏻

My 2 door yaris has full underbody panels and the handling and mpg improvement is very noticeable since stock these things have no panels and are essentially parachutes underneath

I love this!

My only critique of this is that we aren’t able to see the benefit of each individual modification. Obviously the gains are impressive, but I would have been interested to know what percentage each modification contributed.

Great instruction video 👏🏻 I’m glad RUclips brought me here:D I’ve been considering similar modifications on my daily drive Škoda Felicia 1.9D for a while. First mod after new tyres was upper vent cover, and now I’m planning to cover more underneath parts

I expected some Vortex Generators before watching.
We tried a VG geometry similar to Airtab's VG's in our universities Shell Eco-marathon/Efficiency Challenge car and it was promising in CFD. But had to pause the project because we didn't have any time left for Wind Tunnel/flow-vis/cotton thread testing before the competition.

I’m glad you were able to close off so much without the heat becoming an issue for braking, and engine cooling.

This gives me confidence that investing in aero mods is making a difference.

That's really impressive! I'm definitely going to fit the engine undertray that was missing on my car when I got it!

Good job, man! Additionally, you can further improve the drag coefficient with more aerodynamic outer mirrors, changing the door handles for flush ones and lowering the windshield wipers into the bonnet. Thanks for your valuable contribution.

Thats the awesome part of being an engineer and know what u r doing

😂 I picture the conversation with the technical inspectors (TÜV) - but it must have worked out. Very nicely explained

Awesome videos and great enginerring. I have a VW Polo with the 1.6 TDI. Like the last one ever sold. These engines are so awesome. Had the Passat with 1.9 TDI as well. Just awesome quality. I can use some of your ideas.

Impressive project. Also cool thing you mentioned that you removed the mods before selling to avoid fire hazard for the next owner.

Very interesting project. I used to own a BMW E46 320d and it was also really economical and I hypermiled it a lot. I was able to bring the fuel consumption down to 4.7l on my commute to work (country/highway roads with max 100km/h). At normal Autobahn speeds on my trip to France (120-160km/h) I managed 1000km with 5,3l/100km
I'd wonder how much could be achieved with those kinds of modifications on this model.

This is very cool! Thanks for sharing, I’m impressed with the gains!

Awesome! I didn't expect it to be that much more efficient. I also think it looks really sleek and cool without the roof rails and with the moon disks!

Impressive results. It is interesting that you didn't sell the car, in the modded state for more. I would consider your use case to be quite beneficial to many.

You have presented it very well like a case study project

Great job, and inspiration.
An Electric Vehicle that relies on Regenerative Braking, wouldn't need cooling at the wheels, and I love the look of moon discs. So I guess they are in my future. Thank you.

The seals around the bonnet edges, I think, would increase drag. Those gaps allow air to leave the engine bay and that would reduce drag by reducing the force required to make air enter the engine bay through the front radiator vents. In some extreme cases, if you seal the engine bay too well, the engine bay pressure rises so much that it is greater than the pressure at the front of the car and you get reverse air flow. The seals at the rear of the bonnet (near windscreen) should be retained though. The bonnet-windsreen interface is usually a high pressure region so isolating the engine bay from that higher pressure is a good practice.

Great video. Done this stuff to my Lexus 10 years ago. People this does work.

Amazing efficiency results!

I coupl probably extract more efficiency from my 63 Corvair Monza, i dont have brake ducts or front intakes to deal with and mist of the vehicle is flat on the bottom. Could definitely use the wheel covers and maybe a adjustment to the front lower area.

This was way more interesting than I expected

You can get similar gains in fuel efficiency by other means (depending on the car). for example, I used to hae a 1072 Triumph Dolomite 1850 with a 4 speed manyal gearbox. In these cars the exhaust is particularly restrictive, so I replaced it with a rally spec exhaust and downpipe. Nothing else was done and average fuel economy improved from 30 mpg to 36mpg (UK gallons) and there was a modest improvement in performance.
The other case ws on a 244 Volvo (B21A engine and 4 speen manual gearbox. I knew the car would need a new clutch soon, so with the help of the 240 specialist in the Volvo enthusiasts club, I also replaced the gearbox with an Overdrive one (0.67 overdrive) at rhe same time as the new clutch. Again nothing else was changed. this time fuel ecinomy improved from an average of 28mpg to 34mpg. Granted these would probably have cost more than in this VW's case (A custom rally exhaust and downpipe is NOT cheap, neither is an overdrive gearbosx an a new clutch) but the results were just as wotrh rthe expense as I kept these two cars for another 5 years or so.

Sehr interessantes Video, ich bin grad in einer sehr ähnlichen lage und optimiere meinen T4 1.9 td auch auf Verbrauch. Die Aerodynamik habe ich noch nicht angepasst, bin aber durch Anpassung der ESP und durch eine sehr lange Übersetzung jerzt bei 5,2L bei 10% Stadtverkehr, 20% Landstraße und 70% Autobahn bei 100km/h. Durch einen größeren Pumpenkopf und Anpassung des Spritzbeginns habe ich den Mitteldruck erhöht und den MFB50 näher an OT gebracht.
Das Fahrwerk habe ich auf eine möglichst gerade Spur eingestellt und die reifen (195/65r15) mit 3,8 bar bei maximalem Druck.
Ich fahre täglich 180km Strecke zu meinem Ingenieurspraktikum wo ich in der Motorentwicklung Arbeite und am Wochenende 380km in die Heimat.

Great video!
If only the standard customer would have just a little technical understanding, manufacturers wouldn’t need to oversize most components. Cars would be cheaper, lighter and more aero.

I always wanted to do this
So cool to see someone actually do it
Awesome work
And the car came out looking AMAZING as well

It's coll that when I look at my 2015 Polo TDI, and compare it to my 2002 Golf Variant TDI, I see lots of elements that are similar to this video. No wonder the thing is so frugal if I drive slowly.

I had the same engine in a Skoda Octavia 1.9 SDI (yes, no turbo, but it was primarily used as a taxi). I sold it after 240,000 miles when the water pump broke although I wish I had kept it. (I didn't know about the problems associated with DPF'S.)
These engines are known to be bullet proof and the cars and associated parts, very reliable.
I can understand you reducing brake cooling to reduce the drag coefficient, but is this really economical when you consider the extra load put on the clutch and gearbox? I would rather pay an extra few pounds (in the UK) every time I fill up and replace the brake pads every few years than get a large bill for a clutch or worse.
I'm sure you saved overall, but few of us can bank these savings for the moment the clutch needs renewing.

Straight to the point well done on the mod ! I presume the engine was the BXE or BKC ? Have you any insight as when PD injectors are done for a rebuild (km or liters) ? What would be a majoring factor for earlier service of them ? What should indicate replacement ?
Any related advice ?
Many thanks.

Very interesting.
“I’m a quick driver”. Best way to reduce fuel consumption with *no work at all* is slow down 😂. Changing driving style is the the single most effective way of reducing fuel consumption.
I have a W220 S320 Mercedes. During recent fuel shortages because of strikes in France I reduced my average consumption by 15% (down from 8.6l/100km to 7.3) just by driving at 70 instead of 85 in an 80 limit and 100 instead of 115 in a 110 limit and accelerating more gently and planning ahead better. At the time everyone was driving more slowly and more carefully for the same reason. It didn’t even impact journey times significantly. I very regularly use my car for the same 105-km journey. Typical journey times roughly went from 1h12m to 1h20m. As you say use case is also important.
It’s a great argument for taking driving away from drivers and putting it in the hands of AI; robots would do the job far better…

Interesting video. I have a electric Citroen Berlingo van. They were not designed to be EV's, and seem to have had no extra attention paid to the aero. Once it's warranty runs out I intend to try some of these mods. It looks like there is a lot of room to reduce drag to me.

I love this video so far, but you've said you added more toe in than OEM specified for "better handling"?
I do agree adding a little bit in the rear might positively effect the grip on that axle, I'm pretty sure that more toe in on the front will not make it handle better
It will make it a tad more stable in a straight line, less nervous, as having a slight bit of toe out would make the steer in response more, well, responsive, too responsive for most people
But I was always under the impression that having almost neutral toe on the front is the best for sporty driving, just enought toe in to not feel nervous, but not too much to make it react sluggish to the steering input

Nice video. I have the same 1.9tdi passat. Learned a few new things about it :D Thanks!

Very, very interesting. Thank you! I would be curious about how much each individual modification made to the efficiency improvements, though. Nice work.

I've seen this being done to other cars too and now I kinda wanna get a car to do this with. Tbh the moondisks with the whitewalls look pretty good on the Passat of this generation as well lol

1.9 pd can be a mpg monster of tweeked correctly. Big issue with them is the under car drag. If you can improve the under running air flow you will see massive upon massive mpg improvements. Well done with the underplating.

Great job. It would be interesting to measure the impact of every modification and known which one make the greatest effect. Did you do some modifications in your current car? Looking forward to it

That is amazing and the car was fantastic!!!

There’s a guy in like Oregon or Washington in the USA who claims to have gotten an old F250 over 25mpg (would have been like 15mpg or worse normally) with similar ideas. Covered all the undercarriage with plates, built a custom lid for his bed that was aero, put in a button starter so he would never idle, removed the a/c and a whole bunch of other parts to drop weight. The truck was functional but not really as a truck anymore. It’s funny because he could have just started with a car that got better mileage, like in this case.

If the average person applied you methods, the following conditions would be likely.
1. Excessive break pad wear.
2. Warped break discs.
3. Hydro locked engine. (Most drivers don’t think about big puddles)
4. Blown head gasket, or over heating engine damage.
Glad you warned that your mods were based on your driving needs. Unfortunately manufacturers have to try and design for those that pay no attention to conditions or maintenance.
Your success shows just how much performance is lent on the table.
Just out of curiosity, was your car one of the dreaded diesel gate cars?
I enjoy your videos, thanks.

Das ganze hat mich inspiriert auch etwas an meinem Fahrzeug zu verändern (Golf 7 GTD Variant), auch wenn es das exakte Gegenteil ist. Mein Problem waren sehr hohe Öltemperaturen bei Vollgasfahrten. Ich habe also alle Dämmungen entfernt und den Unterboden gewechselt um mehr Luft in den Motorraum strömen zu lassen zudem habe ich auch das Öl zu einem dickerem gewechselt um den Motor bei diesen Fahrten zu unterstützen. Seit dem bleibe ich wenigstens unter 130 Grad Öl. Den Rest muss der Ölwechsel alle 7000 Km richten. Der Verbrauch ist natürlich gestiegen.
Die Woche über bin ich eigentlich nur innerorts unterwegs, hier merkt man also wenig von den Änderungen. Am Wochenende habe ich oft ca 180+ Km offene Autobahn. Hier schaffe ich es nur selten den Fuß von Gas zu lassen und bewege mich meist über 230 km/h Tacho.

I changed tire size from 205 to 185 and the fuel economy improved a good amount, less rolling resistance, I also installed turbine wheels from an older Mercedes that look similar to your moon discs.

Wow that was quite a big fuel saving for so little change... But I guess every little bit help :) Also the car looked cool lowered with the moon disk and more clean exterior.

This is awesome! I showed my dad, he drives a 2010 Passat wagon with petrol engine and DSG. He says he gets about 33mpg US at most. Similar climate in SE WI it sounds like, but his driving is a lot more urban than yours.
Still, some cool ideas and the car looks good too!

I love this. Inspires me to follow your thinking path.

I'm watching with apt interest. I recently bought an Atlas Cross Sport VR6 4motion and have been very disappoint with the fuel econony. Almost 10,000 miles worth of driving and most fuel fills don't even last 300 mi. VW's claim was 18 mpg city and 24 highway. Idrive all highway but about 30-40% of those miles are in LA so really mixed. I think I've had one tank that averaged over 20 mpg but just barely. I've only seen my dash display show over 21 like 3 or 4 times. It usually averages out to about 17.5-18.5.

Never understood how optimised these cars are from factory for efficiency, really impressive

Excellent engineering effort

Holy cow!!! 80 mph fuel consumption is in the Prius's area. Impressive to say the least. Imagine a dedicated body panels and chasis designed for reducing aerodynamic drags - for example, complete under body panels; front and rear wheel well covers; sides mirrors replaced with pinhole cameras.

Very intersting! Roughly 20% better, impressive 🏅

I really like little projects like this, well thought out! I have a California van with the 110kW TDI engine, my best mod to spare fuel is to accelerate easy and never go beyond 110kph; on long trips on flat land it takes about 6.5L/100km, these days in a more mountainous area and ith short trips I'm at around 7.8 combined sadly, and I don't see any easy legal mods I could do to lower that.

Easy and informative!
Great job, as usual!

Very cool! nice to see such a video, gives plenty to think off ;)

I remember seeing one of the larger VW models parked in the German town of Husum that reminded me of the one in the Video.
I most likely saw it in late '23 or early '24 and i remember that it had the results of the improvements as stickers on the side...
I clicked on the Video cuz i thought that it could've been you but then you said you no longer have the Car...
I guess we will never find out😅
Anyways, cool project👍💪

Ich glaube 2017/2018 habe ich das Auto mal auf der A9 gesehen.
Finde Tuning mit Köpfchen ganz toll :)
Man hätte noch den 5. Gang verlängern können, aber deine Verbesserung im Spritverbrauch ist auch so sehr sehr beachtlich!

Great work and an mazing efficiency improvement.
Didn't think you could make such a big impact with small but clever mods.
You mentioned "toe in" for better handling. By better handling you're reffering to better stability/predictability on fast roads with little to no bends?

Love your project! You can also add a lower front lip, so less air go under the car. Removing weight from car helps too like lightweight car battery, fiberglass hood no spare tire and lightweight seats.

nice video, quite instructive... i think that I might have, maybe, installed a fan topush some air through the exhaust system 'tunnel', maybe hooked to the switch for the radiator fan, so that it would provide a small airflow in that exhaust tunnel, whenever the car's radiator needed air, normally when stopped, so that you wouldn't overheat rustproofing paint/wax, sound absorption, or interior mat materials...but, hey, just an idea, cheap, efficient, easy, and just that extra bit of margin for safety...

This is 2 years after your upload, but I feel like you could start a bustling vehicle customization shop just by offering all of the aero enhancements in this video to VW owners.

I used to engine brake a lot but I think, Jason from engineering explained said it was a bad idea :/.
So I check in my rear view of there is a car behind, so I can let the car coast to a slow safe stop :).

5:54 interested in extending the number plate forward while leaving space behind creates a pressure neutralising stagnation point.

very nice job man,i always hate thoes gaps between panels, the only thing you got left is change the gearbox and put a 6 speed with custom gears, so engine runs at lower rpm, but we all know thats a lot more easy to say it than to do it hahhaha

This is very cool! I think if you took the roof rails off and did the full moon wheel covers, you’d save an easy 5-10 % on fuel consumption. 90% of us don’t use our roof racks anyway. I gained 10% taking my lumber rack off of my work van, alone.

Fascinating :) Would it be possible to replace the outside mirrors with smaller self-made ones, or would this be illegal? Or even a camera-based system with monitors inside. And the door handles could've been taped over, maybe to get some tiny amount of more efficiency ...