I'm trying to decide if I ought to drive slower to improve my gas mileage. I know, driving slower reduces drag, but I want to actually crunch the numbers to see how much I'd save on gas by driving the speed limit as opposed to my usual weaving in and out of traffic, way over the speed limit.

So my question is: what is the drag coefficient on a B5? If I get that drag coefficient, I'll gladly crunch the numbers to find gas savings and post results over a wide spectrum of speeds to see if it is financially worth it for me to slow down. My wallet has been hurt pretty bad by gas prices lately and I want better mileage, but I really don't want to slow down. I hate my job and the little bit of enjoyment I get during the week comes from hauling a$$ on the freeway to and from work.

So yeah... can someone provide that drag coefficient for me? If I can get this one, I'd be happy to plot out the results for other models as well. I'm going to throw this data into either excel or MATLAB if I can find a working copy of it and plot gas mileage vs speed. Shouldn't be too difficult.

Even if you don't know the drag coefficients but can point me in the right direction to find one, I'd greatly appreciate it. I just don't want to have to put my car in a wind tunnel to get this info.

Word.

 

anyone? this doesn't have to be just for engineers to answer. I'm by now means trying to sound elitist. I just assumed the people that might know this information would be engineers. If anyone else out there has any ideas though, I'd greatly appreciate your input.

 

Set your cruise control on a level road at different speeds.
Set the computer to read mpg.

 

That would work fantastically if the mpg displayed was instantaneous or at least refined it's computations every 30 seconds or so. Believe me, I thought about that. It takes my car about a week to notice differences in my driving that result in +.1 mpg... not exactly the fast changing results needed for this type of a calculation. If that did work though, I'd be able to derive a drag constant pretty easily... but the whole point of this was to be able to derive the difference in mpg at different speeds anyway so if my car had that capability, I wouldn't have started a thread looking for this info in the first place.

 

Press the button on the end of thewiper arm. There is
an instantaneous setting.

 

Thanks. That makes this a whole hell of a lot easier. I didn't realize I had an instantaneous setting available.

 

He, he,

Driving an Audi doesn't go along with fuel savings, (just a general consideration).

 

Oh I understand that my car wasn't designed with fuel economy being the driving design factor. I'm just trying to make the best of a bad situation. I paid 4.60 for gas a couple of days ago and I need to get every penny I can out of my gas tank.

 

Sorry I'm a 'limey' is that $4.60 per US gallon? [8D]

That works out $1.70 per Litre or £0.85 per litre. In the UK we're currently paying around £1.20 per litre which works out $5.40 per US gallon! lol

But, I do know where you're coming from. I've asked myself the same question. And in my experience, it does make a difference. If I drive at 80mph I may only get 32mpg instead of 40mpg on a good day by driving at 70mph. I drive an '00 A6 1.8 Turbo btw. I also found other factors came into play. Wind direction, and climate. Wind direction for obvious reasons but I also found that my motor is more economical during the summer than it is during the winter. Aparently it's something to do with the colder denser air. Also, check your tyre pressures regularly and remove anything from the car that shouldn't there (roof bars, excess boot contents etc). This all makes a difference.

However, I found I could make more fuel savings around town simply by reading the road ahead and anticipating sooner by using engine braking instead of the brakes and accelerating smoothly. If lights are red in the distance I slow down gradually and aim to reach them as they turn green without stopping. I now adjust my speed when approaching junctions and roundabouts and aim for gaps in traffic instead of coming to a screeching stop and have to wait. In stop-start traffic I try to drive at a low average speed without actually having to stop. All this was hard work at first, mentally, buy now it's habbit and can actually be fun![&:] It also makes for a smoother ride for my passangers. Around town I can now get up to 32mpg instead of about 25mpg. I think all this has make me a better driver overall but I now find myself getting frustrated when someone stop ahead of me when there was clearly no need to! [:@]

Hope this helps.

 

Very good advice, and those tactics are effective for sure.