'96 Silverado vs 2009 Outback

[vteco]

I live in a world of hills. Going downhill idling, the Silverado picks up speed very quickly. The Subaru noticeably less so on the same routes. The Silverado bleeds off speed more slowly going back uphill.

The Subaru has all wheel drive. The Silverado has manual electrically engaged 4 wheel drive.

I'm guessing this is the explanation?

[vteco]

Couple other thoughts re coasting:

1.) At least with a wheelbarrow, big wheels push easier than little ones.

2.) Wheel inertia, disparaged under power, especially when needing to frequently brake, is not necessarily such a detriment when largely coasting up and down hills in our area.

Particularly if the wheels are storing energy by retarding speed which might be wasted in braking at curves, where speed buildup downhill otherwise would get excessive with small light wheels.

[vteco]

Third thought. Everybody has different conditions. If I lived in a desert, or a city, or had a long commute, every aspect of working towards reducing fuel usage might be different. I'm shooting towards optimizing a very particular niche set of conditions in a specific vehicle.

[cRiPpLe_rOoStEr]

Wheel inertia tends to be troublesome for overall efficiency, even if it could seem at a first glance to be beneficial while driving through hilly terrain. Fewer usage of the brake OTOH tends to happen once you're already driving in a more efficient way.