Well, I thought I'd front the question here. All through March, April, and into July, I was getting between 42-45mpg, driving in city, average trip about 10 miles (each way to and from work). So about 25 miles a day, 4 days a week. Now, at the end of July, I took a small road trip from Denver to St Louis Missouri. Roughly 850 miles each way. I got back from that trip, having just pushed over my 3000 miles since my last oil change. Now, a little back story, since I bought the saturn last november, I've had all of the oil changes done at the dealership. I was getting a discount, so I figured I might as well. I have no idea what the Saturn dealership was putting in other than that it was the 5w20 that was reccomended by the manual. I've since been told that the normal oil is akin to Valvoline durablend synth blends. I took the Saturn to a Valvoline Instant Oil change and had them just do a basic filter swap and oil change with natural oil. Since then, I can barely get 38mpg, no matter what I do. I have been averaging 35mpg or so since, but I have to drive it very gingerly, and all the tricks that got me 45 before aren't working to the effect they were before. Tire pressure is good (max sidewall), fuel's stayed the same (from the same station every time), and this was a very sudden drop. Would the oil be a likely cause of the FE drop? Would going to a durablend or adding a synthetic stabilizer like Lucas help increase my FE? Thanks for any advice you all can give.