I get about 36 mpg highway with mine, pretty reasonable for an early 00s car that’s a large sedan
I have a 3.4 in my other car that’s at 270k and runs well, but in general the 3.1 and 3.4 are not great. Cracked the block in a 3.1 Sunbird. Was gifted a Rendezvous with the 3.4 which never made it to 130k before epic…