Sudden drop in gas milage...

I've owned my car since August (8700 miles) and was getting around 360 miles before the refuel light turned on. Lately I can barely get to 300 before the light turns on. Its been on a steady decrease for the last month or so from 360 to 300 now. My commute is almost exactly 50 miles round trip with 5 of those miles being local. When I'm on the highway going under 80 I can get upto 31 mpg. If I go 85 I get around 24-26mpg which seems to differ greatly from what you guys post on this thread:

http://www.audiforums.com/m_618540/tm.htm

Is there anything I should be looking out for? Like checking the air filter etc? Any advice would be greatly appreciated because this low milage is really hurting my wallet! One of the main reasons I bought this car was for the excellent gas milage, but now its terrible.

Thanks in advance for any input and happy new year everyone...

Check your tire pressure...but my guess is that the biggest robber of your gas mileage is winter-blend fuel. I am almost willing to bet that around April (maybe earlier, maybe later depending on your location) you will start to see your mileage increase.
 
Another robber of fuel economy is having to run the heater.
 
 

Thanks for the reply. I'm going be checking my air filter and tire pressures tonight.

It has been extremely cold here over the last month here in MA. 20+ inches of snow in december alone. So the heater definatey has been getting a lot of action. But the milage was dropping even before I started cranking up the heater... would winter blend fuel make that much of a difference?

Yep.  Winter blend fuel SUCKS.  don't quote me on this, but I believe winter blend has a higher ethenol content. 
 
Ethenol does not have the energy potention of regular fossil based fuel.  If you want an extreme example, rent a GM vehicle that will run on E85.  Fill up the vehicle with regular gas, run that around until it's time to fill up again.  Then fill up the same vehicle with E85.  The E85 tank will not go nearly as far.  I believe with E85 there is something like a 15-20% drop in economy.  The only reason it is being pushed is it is supposed to be better for the environment and it reduces dependence on foreign oil.

from Wikipedia
 

quote:

Comparisons to regular gasoline
The horsepower a given engine has when using E85 is comparable (or slightly higher in some instances) to gasoline. Depending on composition and source, E85 has an octane rating of 100 to 105 [3] compared to regular gasoline's typical rating of 87 for regular and 93 for premium. This allows it to be used in higher compression engines, which can lower emissions.
E85 gets approximately 25% fewer miles per gallon. In order to save money at the pump the price differentiation between gasoline and e85 would need to exceed 25%. Currently E85 is about 5-10% less expensive in most areas.[4] More than 20 fueling stations across the Midwest are selling E85 25%-40% cheaper than gasoline.[5]

SIGH... I almost wish my sudden drop in milage was due to negligence or something where I could get it back by replacing my air filter or getting it blessed with holy water or something. Maybe if i wash it it will decrease the drag created by the crusted salt all over my car. 

You need to wash that salt off anyway!
 
Like I said earlier, check your tire pressure.  Are you on winter tires?  If so, that will affect your fuel economy too.  You already mentioned checking your air filter, but I can't imagine that it would be too bad.

I dont know where you live E but here in MA, keeping the salt off = washing the car 4+ times a week. I try to wash it at least once a week. We have snow banks reaching 4ft here and its going to be 60 on tuesday. That means puddles everywhere... I'm washing the car today for sure but it will only last me through the weekend if I'm lucky. Than my black car will be white again.

Check out this link for ReFormulated Gas (RFG)
 
It is from the EPA website
 
 
Another thing to keep in mind during winter driving is that people tend to drive a little slower, so traffic is a little worse, so there is more stop-n-go, and more time spent idle-ing.
 
Winter blend
winter tires
heater
higher percentage of idle time
more frequent tire slippage (if driving on snow)
 
all of these things can add up to a fairly significant drop in fuel economy.
 

Yea E85 doesnt get as high mpg as gas, but E85 is also $1.30 a gallon in my area. Whenever I drive by the pumps are PACKED. 25% loss in mpg but almost 200% cheaper, sounds like E85 is the better route in terms of cost. The new Koenigsegg CCXR makes over 1000bhp running on E85 which can prove cars can be just as powerful running E85 as gas if the mechanics are designed correctly.

Will the A3 run on E85 gas without any adverse side-effects? How about 100 octane gas?

100 Octane is ok. I wouldn't try E85.
Here might be a reason for mpg drop.
Your DV valve my have froze and then ripped. Losing boost preasure, loosing power thats not truly unnoticed but could effect your MPG's. I would take it in and just have them check it just incase. It is under warranty and they my find the problem. Since it got cold here I got an extra 2 mpg.

Cheaper burns cleaner, but burns faster. in a nut shell
 

+1 on getting the DV checked. Also, does anyone know if Audi corrected the PCV problem on the newer models?

Regarding E85, I don't think the A3 would handle it properly unmodified. The A3's ecu is very good at adjusting fuel flow and timing based on what gas you are running, but since E85 has less energy potential per gallon than gasoline, it would require more of it to make the same power. I don't know if the A3's fuel pump or injectors are up to the task (fuel cut with chip tune, anyone?). That being said, if one of the tuning companies made a tune specifically for E85 and coupled it with high flow injectors and fuel pump, this car could make some crazy power! The higher resistance to detonation would allow you to run unheard of boost (higher than race gas). It's not unfeasible, most chip tunes now allow you to switch between multiple 'programs,' or fuel maps. I think the primary limitation would be how much boost the 2.0T can hold.