Help Me Explain this

[WorkingOnWise]

This is a long post, but please take the time to read it and offer up any words of wisdom you have. If it is what it is, great! If it isn't, I have got to learn what I am doing so wrong!
Ok, I have a 1995 Mercury Villager GS minivan with a 3.0L V6, an automatic transmission with overdrive and a lockup torque converter, and 140k miles on it, and it weighs 3800lbs (by manufacturers stats. I will be weighing it tomorrow as part of my baseline information) It has 4500 miles on the petrol based engine oil and napa oil filter, it needs a set of tires pretty soon (one tire has a low speed shimmy - sure sign of a shifted or broken belt), and it is bone stock.
It runs great, but at idle it has a very slight misfire, so I'm sure it could stand a fresh tuneup. I have no idea about the age or the air filter, but it at least passed a visual inspection.
I tell you all this to show that it is your regular old well cared for minivan. Nothing at all to think that it should perform in any way out of the ordinary.
The EPA said in 1995 that it gets 23mpg highway, 17 city. When I saw those numbers, my heart sank a bit, because I realllllly want 40mpg from this van. I have heard a few here and other places wish me a disbelieving good luck.
Which brings me to today.
Today was the day I was going to get my baseline mpg so I could officially launch my business, which is selling mpg improvers that have been tested by me, and actually work. If I find it to be junk, I will be more that happy to tell anyone who asks!
We filled up at the BP on M28 and F13, then drove down F13 to US2 and into Rapid River. We turned around and headed back to where we started from. Denise wanted to go look at a scenic stop and I told her if we did, we would have to stop there every time we did a mpg test, so we dont throw the results off. Well, my wife is pretty girly, and is very good with having to stop at the same pretty place every run.
It added 14 miles to the test run, so that was fine. It was still 55mph, as is all the roads we use on our test route, so it was still a highway speed test.
It was 70 degrees f by now (2:20pm) and getting sunny, so driving in no shade and no AC and the windows was beginning to really suck. We dropped both windows for that 14 miles to cool us and the interior of the van off. In my mind I am trying to imagine the brutal impact it was having on my test results!!)
Once we got back on US2, the windows went back up and the fan went back on, still no AC. Well we got back on F13 and headed north to the BP where we had filled up at in the beginning.
We chose F13 instead of M28 for three reasons. One, it runs right thru a national forest and has pretty good shade for most of its 37 miles. Two, it is a kind of curvy road with constant trees on both sides, so the wind really cant affect the driving. Between the curves and trees, it is nice and calm. Third, it is fairly hilly, which isn't great for big mpg numbers, it does help with giving a more realistic highway test, at least in my mind. We just set the cruise at 55mph and kept the van away from the trees as we went down the road. No tricks to help the mpg, even when they really would have mattered, like when the van had to climb the 6 hills where the cruise computer increased the throttle so much that the transmission dropped out of OD and down into 3rd.
So, theres the scenario for you.
When it was all said and done, my mpg for that 114 mile run, was 30.5 mpg.
I had seen another pretty impressive number from this van last month when we drove down to Indian River, about 160 miles. On that trip, we got 32.2 mpg. I checked the distance against both gps and a paper map, and reverse calculated the fuel used and fuel paid for, seeing if the pump was maybe off, in my favor (I know I know, fat chance!) because I just didn't believe it. We drove the same way on that trip as we did on todays test run, and 32.2 was the number. I dismissed it as some variable I was unaware of and therefore couldn't control, which was whacking my results.
But today I got 30.5. And Saturday we drove a total of 112 miles on a trip to Marquette and back, including 16 miles of driving around in the city, up and down some pretty stout hills, with 4 adults tha whole way, which added 400lbs to the vehicle weight over what it was today. On that trip we managed to get 26.5, and we weren't even thinking of mpg. We were just out for a fun day with the family.

So, what in the world is going on that I am getting a repeatable 30+ mpg from a van that, when it was brand new, the EPA only managed 23 mpg from?