500 mile trip - impressive MPG and trans questions...

utvol1984 · Post by **utvol1984** » 17 Jul 2006, 11:03

Just completed a 500 mile mostly interstate round trip with my 93 850 GLT and achieved 32 MPG highway which I was very happy with. I get about 22 around town - is that consistent with others?

Also noticed that at times auto trans seemed reluctant to shift back into OD after going up a grade. I noticed that in OD at 70-75 mph, tach was around 2700-3000 RPM. When it seemed to stick in 3d gear, RPMs stayed around 4000. My tach works about half the time - seems accurate when it's working and just flops to 0 when it decides to take a nap.

Do my RPMs sound about right for 3d gear and OD? Does anyone know what might cause the trans to balk at going back into OD? I run it in "economy" mode all the time - never "sport" mode. Recently flushed trans fluid and replaced it and the fluid level is good. Also, trans seems fine in around town driving. Insight on my balky tachometer would also be welcome.

Thanks!

l33tDad · Post by **l33tDad** » 17 Jul 2006, 13:17

I've also got a '93 850glt and all my numbers are very consistant with what you list. I get about 32/33mpg traveling on the NYS Thruway at 70mph and in the low-20's around town. My tranny also seems to have a "difficult" time shifting into OD after going up a grade.

M81388 · Post by **M81388** » 17 Jul 2006, 13:52

I get around the low 30s too, and the transmission (when in cruise control) will downshift on a grade, then will not upshift back again untill well after passing the climax of the hill.

nitink · Post by **nitink** » 17 Jul 2006, 23:29

You are lucky guys. I am getting 17-18mpg in mixed driving, Whenever I press Shiftlock I haven't seen any change in RPM, At 65MPH mostly engine is @ 2500 rpm

utvol1984 · Post by **utvol1984** » 18 Jul 2006, 07:03

Thanks very much everyone - it helps to know that my numbers are in line with the typical 90's 850. I have one more question and it's probably kind of stupid - what is the "shift lock" function? I assume it keeps the transmission from upshifting when engaged? I have the little shiftlock button at the top right of the gear selector but I only use it to "unlock" the shifter so I can take it out of park (have not gotten around to replacing the little shift lock relay/switch thingy inside the console). Thanks again all.

steve · Post by **steve** » 18 Jul 2006, 11:26

Utvol, the shiftlock button unlocks the shifter. It is there incase the solenoid and switch fails that automatically unlocks the shifter when you step on the brake. To my knowledge it serves no other purpose. Had to have mine repared about a year or two ago.

BTW, my mileage and shift characteristics are identical to yours when in economy mode.

S

utvol1984 · Post by **utvol1984** » 19 Jul 2006, 07:35

Thanks Steve - good to know that my car behaves similar to most others out there of the same general year and mileage. Thanks for the tip on the shift lock also. Like I say I have had to use it continually since I've had the car. I have the replacement part to fix the shift-lock problem but just have not tackled that project yet. My car needed a lot of work when I bought it - mainly front suspension. I got that all fixed up tight and the AC issues resolved, now I'm moving on to smaller stuff and hopefully some body work.