D = Drive. Usually locks up the uppermost gear, which is overdrive. (D) = Overdrive. A gear in which the output is greater/faster than the input.
I'm not familiar with the transmission used in the Taurus, so I can't really say much more. But it sounds as if your overdrive is failing to engauge. Are you sure gas mileage hasn't dropped? If you are not going into overdrive anymore, your engine will be running at higher RPM while cruising and this will consume more fuel.
Wait until you get a response from someone more familiar with the Taurus, as I drive older, bigger Fords with the AOD transmission, or the C6 transmission (1987 Lincoln Town Car, 1971 Ford LTD).
-Steve
I have a 94 Ford Taurus (3.0) and I have noticed lately that my car
> reacts exactly the same no matter which of the D s on my shift
> indicator (automatic trans.) Now... if I go down to the 1 position...
> you can definitly feel the difference. I used to feel the difference
> in driving in both Ds.
>
> Now... I know this is transmission related, and I do NOT have any
> money, except to maybe change the fluid/filter.
>
> Here are my questions.
>
> 1 ---
> There are two D s on my shift indicator, I know one is for DRIVE...
> but what does the other D stand for?
>
> 2 --- My car has about 148,000 miles on it. I know that NOTHING has
> been done to the TRANNY since about 88,000 miles, when we did a
> fluid/change. Can old/dirty fluid and/or filter cause this type of > symptom?
>
> 3 --- What do you think is happening here? Am I somehow stuck in LOW
> or something because I have very poor pick-up from a stop. My mileage
> is fine, but the pick-up is terrible.
>
> Again... I used to feel a difference in driving between the two D
> positions... and now... they are exactly the same as far as feeling
> and driveability go.
>
> Any educated guesses guys?
>
> thanks so much.
>
> LEESA (I)