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Discussion Starter #1
I have a 09 TDI/manual that has 10400 miles (95% freeway). My problem is is that I seem to be getting lower and lower mpg then when I first bought it. I drive 50miles (95% freeway) to work and from work 3-4 days a week. From the time I bought the car up to around 9000 miles, I was getting, on average 54-56 mpg according to the MFD (that with the cruse control set around 63mph). I took the car in for its 10000 mile scheduled oil change and ever since then, I am getting 49-51 mpg and I dont understand why? I have filled from the same gas station since I bought my car, I keep the tires inflated at 38 psi and still driving around the same speed. Can anyone give any insight into why this may be happening? Has anyone else experience this? I keep reading that I should be getting "better" mpg because my engine is still "breaking in" but for some reason, I am not.

Please help!
 

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Lower MPG

Is your car performing the same as before the service? You might want to check your oil level. I've heard numerous stories of dealers overfilling TDIs with oil when servicing. Or worse, using the wrong oil. I'd check it just to be safe but either way contact your dealer and explain your concerns.
 

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2nd check the engine oil and post what part number they used for the oil.

Thicker engine oil will lower fuel economy.

Winter fuel is cut to lower the gel point and will also lower fuel economy. This is the only thing I can think of.

There is no obvious reason why your fuel economy is going down. Your fuel economy is already at the upper end of the bell curve so I don't think it's your driving style or any quirk of that particular car and I would expect it to stay there.
 

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Yep, there's no reason for mpg to go down from here on out. If they changed the oil they must have done something. Do the rear wheels spin OK? I know that some cars were delivered with the handbrake too tight. If you don't use the handbrake it doesn't reset the rear calipers.
 

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Discussion Starter #5
I checked the oil level last night and they did not over fill the car with oil. And chittychitty, I looked on the work order and they used part # G-052-195-1L which is the Castrol SYN. LL03 5/30 (507 00).

You had mentioned something about the winter fuel and I started thinking the same thing but I do not know.
 

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How do your wind patterns change seasonally out there? I've noticed head winds, side winds, tail winds all affect my mileage, sometimes dramatically. You're in the desert, I think, so I'm guessing your fuel hasn't been winterized yet. Here in Indiana it is supposed to be Dec. 1. I'm still learning about diesel fuel quality. It's almost impossible to find out any information at the stations. One knowledgeable owner said that sulfur acts to extend storage life and the ultra low sulfur diesel doesn't last as long in the tank. I know some stations buy it from a number of different sources so the quality is bound to vary as do, I assume, different batches. I'm wondering if air temperature affects mpg, as cold air is denser. I make long flat interstate trips each week and on good days (wind cooperating and traffic) I get in the low 50s if I stay around 65 mph. I have 16k and my tank averages are around 45 mpg for the past few months. I know that will change when the cold/snow/winterized fuel arrive!
 
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