- Sep 23, 2007
My mom's 2005 Jeep Grand Cherokee originally called for SAE 5w30. She got 19.1 MPG according to the computer in the dashboard. I switched the car to 5w20, and the computer started to show 19.9 MPG. I would never have tried this if the later versions of the Grand Cherokee never called for 5w20. The engine in those later Grand Cherokees is the same as the earlier one, except more smog equipment is added.