Yes they are reliable and they do get good fuel mileage. Right now in town on my Trooper with 2.6L Im getting 24 MPG. I havent had the Trooper on the highway yet but hope to soon, very soon. Valves must be checked at 10 to 15K miles or they lose power and fuel mileage sucks. They have some Bolt on performance to get some more power out of them. Header, K&N Filter, exhaust helps a lot. From the factory they are rated with 120 HP. Like strawmeyers is saying Its like running a Shipping crate down the interstate. Or like Running into a head wind with a large piece of PlyWood.