I only really use my Volvo 960 for the highway. Being I hadn't had the car out of the garage since mid January I figured she needed a good run to get all the fluids up to temperature and charge the battery. So I went out on a three hour interstate run Saturday evening. Being this car is 98% interstate at 60-65 mph I have never really noticed the coast down aero advantage.
So I'm heading home, I see my exit off the interstate, disengage the cruise control and coast from what I thought was far enough back from the exit.
The car barely slowed down from 55 mph to 40 mph. If it wasn't for the grade on the exit it wouldn't have even slowed to 40 mph. I was amazed at how little the car actually slowed in the distance I traveled with the cruise control off. From the exit to home I kept seeing the free wheeling the car had. It was really noticeable between 40 and 55 mph. At 65 to 70 it's there but you really don't notice it. Under 60 mph you take your foot off the accelerator you do notice the effect.
Did the same thing with my 740 wagon today. Same speed 55 mph, exit, plus the cruise control was disengaged at a shorter distance before the exit. Gee even with the clutch in the car slowed from 55 to 40 mph like right now. I had to use the gas pedal to get up to the light at the top of the ramp. Didn't have to do that with the 960. Basically the same chassis and the 960 weighs in at least 500 lbs more. The 740 wagon is lowered, the 960 is not. The Cd of the wagon .39 the 960 .36. This proves to me is there is a whole lot of air drag on the undercarriage of the 740 wagon. The area around the rear axle and the rear bumper is a killer on the aerodynamics.
If you said, I couldn't find anything on whether the 960 is an automatic or a manual. My suspicion is that it's a automatic.
With my wife's Chrysler, Town & Country, it is an automatic and they have done something which gives the impression that it just coasts very far. I think what they did is something to hold the throttle open, just a little and feed a small amount of fuel in. In any case, it coasts a lot farther in gear than it does in neutral. My guess is that you may be experiencing a similar phenomenon.
Sectional density from ballistics, more weight equals more inertia. The longest coasting car I ever owned was a 95 Buick Riveria which got as high as 28 MPG. That car woud coast over a mile from 60 MPH,in neutral, and it required me to modify my driving habits letting off the gas sooner to keep from having to apply brakes. 3800 pounds with a 3.8 liter supercharged V6, rode so smooth it was hard to not fall asleep driving that one.