Hello old friends, I have an issue with my transmission and before bringing it to the stealership is like a little knowledge on the matter.

Noticed recently my gas mileage went down the shitter and couldn't figure out why. Tonight I noticed when I shift my car into drive it stays stuck in 3rd. If I fuck with the shifter enough it'll eventually go into drive but even the lightest tap will push it back into 3rd. I've looked shit up and the answers are pretty wide ranging from changing the fluid to a bad ECU. Whatever it is I'm hoping it's cheap. Any input would be appreciated.

Cheers

Bad gas mileage because you are driving in 3rd gear lol, it's probably the shifter itself. Check this video: https://youtu.be/MJW08kFNUyI

Seems like a gasket in there dislodges, which would cause the shifter to not engage properly.

Check the linkage too, sometimes it gets messed up and wont let it go into drive all the way.