Waxed car vs non waxed vs mpg

If you regularly wash and wax your car you might also detail the inside, which might unload extraneous stuff. This could lead to weight reduction that could result in higher mpg though it would be marginal.
 
You'll never be able to discern the difference outside a margin of error as there's just way too many variables. The biggest variable is the dupe driving it. Beyond that, changing ambient conditions alone can make a 2 mpg difference regardless of the driver variable. Changes in fuel from one batch to another can have that much affect as well, much more the differences in summer and winter blends.

The main reason racecars are squeaky clean and sparkly is for the sponsor. No company wants to put their name on a dirty car. There is a slight affect on aerodynamics but it's very minor. A 1-2 psi change in tire pressure has a far greater effect, that's if you can control the variables above.

The majority of the theory on better fuel economy with a clean car is the placebo affect. You want to think your time, effort, and money invested in cleaning and waxing the car has an impact on something other than just looks when it really doesn't.
 
I was wondering if anyone has tried this theory of increasing mpg by making sure vehicle is always clean and waxed. I noticed in my Accord, it seems like it has increased, but not yet actually run the calculations

Myth busters said they saw an avg of 2mpg. My brother in law works for Boeing and he was telling me an aircraft will loose 5% fuel efficiency with a dirty aircraft. I know race cars are always clean and waxed.
5% on an aircraft doing 400+ knots and where the losses are all aerodynamic

only a few cars manage 50 knots average, and even then the aerodynamic losses might not be the major force to overcome. we're talking fractions of a % improvements at best. Or, even worse is possible, as the boundary layer could become so big the airflow detaches whereas imperfections could help to keep the boundary layer shallow and air flow attached.
 
I don't know about cars, but back when I was working in the 80's, my plant superintendent owned and flew a Piper Cherokee Six. I believe it had a 300 H.P. engine. He had the aircraft completely repainted because the paint job was severely faded, and even started to peel and flake in certain areas.

After the repaint, (the airplane looked beautiful), he told me that it would cruise almost 5 knots faster with the same power setting and altitude. I had no reason to doubt him. YMMV.
 
Sometimes people falsely credit a MPG improvement to something ineffectual when what they really did is change how they drive. Something many people are unaware of is that there are tires with low rolling resistance that help increase fuel efficiency. Such tires are very populate as on new vehicles. I saw video how one tire maker test such tires, they coast a vehicle down a slight hill until it stops and measure the distance.
 
Back to cars. What makes me question that a super high gloss finish is beneficial to less air resistance on a race car, is now it seems a lot of Formula 1 teams are going with a flat paint job. Or else a flat finish that they're not trying in the least to make glossy and slick.

Red Bull and Ferrari are 2 good examples. Both have flat, non glossy finishes on their cars. These guys spend tens of millions of dollars testing everything under the Sun, in order to gain the most microscopic advantage speed wise.

If a gloss finish was that important to obtaining that, those cars would all shine like mirrors. Another example are all military aircraft. Including the very large transports like the C-5A and the C-17. They all look like they were primed, then they ran out of money, and couldn't afford to paint them.
 
If you regularly wash and wax your car you might also detail the inside, which might unload extraneous stuff. This could lead to weight reduction that could result in higher mpg though it would be marginal.
Not measurable would be the word.
 
I totally understand the skepticism on this subject. And I absolutely agree that tire pressure can make more difference in fuel economy than many other factors.

But I thought the whole reason that large ships have barnacles scraped on a periodic basis is for fuel economy. Of course we aren't talking about barnacles on our cars, but instead the difference in surface area smoothness probably in the 10th's, or even 100th's of .001".
 
I totally understand the skepticism on this subject. And I absolutely agree that tire pressure can make more difference in fuel economy than many other factors.

But I thought the whole reason that large ships have barnacles scraped on a periodic basis is for fuel economy. Of course we aren't talking about barnacles on our cars, but instead the difference in surface area smoothness probably in the 10th's, or even 100th's of .001".

The barnacles on the ship are much more dense and rough. They're also in water which is 800x more dense than air creating a lot more drag. On top of that, the hull is constantly in contact with the moving water.

The dirt on a car (assuming simple dirt and not caked on mud or something) doesn't have nearly as much impact. Furthermore, the areas where dirt will collect like on the hood and roof don't see very much air flow at speed anyway as the air is shot over the hood and roof by the front bumper and windshield. That's why dirt collects there.
 
The barnacles on the ship are much more dense and rough. They're also in water which is 800x more dense than air creating a lot more drag. On top of that, the hull is constantly in contact with the moving water.
Yeah if someone needs a graphic demonstration, try running in water and compare that to running in air.
 
Back to cars. What makes me question that a super high gloss finish is beneficial to less air resistance on a race car, is now it seems a lot of Formula 1 teams are going with a flat paint job. Or else a flat finish that they're not trying in the least to make glossy and slick.

Red Bull and Ferrari are 2 good examples. Both have flat, non glossy finishes on their cars. These guys spend tens of millions of dollars testing everything under the Sun, in order to gain the most microscopic advantage speed wise.

If a gloss finish was that important to obtaining that, those cars would all shine like mirrors. Another example are all military aircraft. Including the very large transports like the C-5A and the C-17. They all look like they were primed, then they ran out of money, and couldn't afford to paint them.

The barnacles on the ship are much more dense and rough. They're also in water which is 800x more dense than air creating a lot more drag. On top of that, the hull is constantly in contact with the moving water.

The dirt on a car (assuming simple dirt and not caked on mud or something) doesn't have nearly as much impact. Furthermore, the areas where dirt will collect like on the hood and roof don't see very much air flow at speed anyway as the air is shot over the hood and roof by the front bumper and windshield. That's why dirt collects there.
You also get a lot of dirt on the rear bumper from the dirty air coming off the car. That's the mixture of the air coming off the roof and the air that's coming from underneath the car and creates a tornado effect
 
Well maybe if I knew somebody on a formula One team who had a wind tunnel we could settle this argument

For something like Formula 1 or NASCAR where you have an average speed of >150 mph and very tightly controlled chassis and engine design, any advantage they can get is worth it no matter how small. Some of those teams will spend millions to find 0.1 hp, 0.1 mph, or 0.1 mpg. The casual Toyota Camry going 65 mph on the highway will never notice the difference.
 
Only if you have a perfectly flat road. I can usually get 3-4 mpg better than the cruise control.
I find if I set the cruise to speed limit. Then as i go down a slope slowly rolling on to the power to gain more mph 5-7. When I climb the next hill and hit the peak at or just above posted speed that i can increase my fuel mileage.
This tactic is obviously not recommended in all settings but at 1 am on my 16 mile drive home i watch for traffic behind me.
I can see cars miles back if they are catching me.
 
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