If your daily commute is stop n go city driving, get a hybrid.  If you need to get on down the road,  TDI is the way to go.

An '04 Jetta TDI with an Automatic transmission getting 44 mpg is about 37.5 % better mileage than the 32 combined mpg revised estimate according to fueleconomy dot gov. Pretty darn good.  The EPA is using different, more realistic estimates for vehicles after 2008.  Generally speaking, an auto trans will get less mileage than a manual.

Unrealistic expectation checklist:

• Think that speed limit signs are minimum suggested.
• Got under inflated tires  (hmmmm, when did i check that last)
• Buy poor quality fuel
• Have a canoe ( or anything else) strapped to the roof
• Do your best John Force impression at every stop light
• Crank the AC
• Don't shift until the tach is pegged
• Have your four 200+ Lb friends with all their gear in the car
• Commute to work uphill both ways
• Below zero with winterized diesel
• let  the vehicle idle to "warm it up' or run the AC before you leave ( every time it's not moving you're getting 0 MPG, point to hybrids)

Any combination of the above and you will not get anywhere near the advertised estimated mileage.

I have an '03 Jetta TDI, the 90 hp version  with manual trans and regularly get 50+ mpg.  Ranging from a low of over 46 to a little over 53.  This is actual mileage from miles divided by fuel burn cross checked with a scan guage.  Not one of those hybrid mileage computers that use the new math.

If you have an "04 and above will have the 110 hp TDI engine and will get slightly less mileage than the '03 and earlier Mk IV Jetta .

This is my third Jetta diesel and my first TDI.  I would have kept the last one, but the NY winters had taken a toll on the body and it went to the boneyard with over 350,000 miles on the original engine.  However, it was an organ donor and the engine and trans were transplanted and as far as I know are  Still running :-) 

I will NEVER sell my '03.  I intend to give it to my son for his first vehicle when he gets his license six years hence.  I am it's original and sole owner.  My daily commute of over 70 miles each way, was a mix of  Adirondack foothill secondary roads, I-90 and urban crawl.  I refueled once per week.  The Jetta got me home from Petersburg, VA  to upstate NY without refueling.  -20 below zero, started right up.  No sweat.

I've added a frostheater engine heater.  Where I live it's downhill to go anywhere at first , so on very cold days, it helps the cabin warm up more quickly.  I didn't get it for cold start reasons.

I also installed an aluminum belly pan/skid plate. The stock plastic one is worthless .  This skidplate cost less than it did to have a new oil pan installed after I bottomed out pulling into a car wash.

118K miles and counting,  Just getting broken in.

P.S. Pri(tent)ius owners Call your local Toyonda dealer service department and ask for a service quote to R&R the the NiMH storage batteries.  Do a little research on the dust to dust life cycle of the Nickel in those battery arrays, then talk about how "green" your car is.

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