Roadodmeter records mileage , but does not always light up to display the mileage

Does the mileage light up? give you they mileage, like 123,324? If so look to replace the speed sensor. I don't know your vehicle, so I can't tell where it would be. It could be on the transmission or ran threw the ABS system/wheel sensors.

it should be able to but a lot depends on the engine condition, mileage , good service record , etc i would have the engine serviced and then give it a try and see how it runs can always stop using it if not satisfied

Thermometer

8 dergees BTDC

Hello frumento, Your are describing an advance cluster failure. I have repaired many GM instrument clusters and see your issue come to my shop on a regular basics.
Please visit my website for complete repair information. www.kincerservice.com
Thanks Mike

I have a 2000 malibu ls, and it gets about 27 in city to about 32-34 on open highway.

The light should normally be "off", by pushing the small button on the transmission shifter. For power or passing at high speed, push the button again to light "O/D off", signifying that the overdrive is off. Overdrive (O/D) is normally for cruising at highway speeds to maximize gas mileage. Having it off increases the motor RPM's, increasing power, and decreasing mileage and gas efficiency.

For most purposes turn "on" overdrive, and the light on the dash should go out.

You will have to reset the maintance light. Turn the key in the on position.( Not the crank position ) Push the trip meter button until you see the mileage reading. Now turn key off and with left hand hold in trip button. While holding in the button with left hand turn key to on position until you see dash lights. Hold button in until light starts to blink then after 4 blinks release button for 4 blinks then hold in again until light resets. If it doesn't work try trip A instead of mileage reading.

check fuses first.

set your mileage to current mileage, not A or B, but the TOTAL! then, turn your key off, turn key back on AND press the mileage reset and hold it. you will see lines appear and KEEP holding the mileage button until the lines disappear, 5 seonds. that will clear or re-set your service reguired display.