Even though I usually struggle to keep up 40 mpg at 80 miles per hour, I took a 130-mile round-trip through a small section of the southern California desert and did surprisingly well.

I started near sea level and gradually got to an elevation of 4155 feet; shortly after this, I encountered horrendous crosswinds that made driving the car scary so I turned around. My mileage for the first part was between 33-34. During this trip I maintained 78-80 miles per hour. Battery level was usually at 2 bars but never below; the car quickly gave up on using IMA and let the engine chug along at 3000-4000 rpm. At one short but steep part I was maintaining about 5200 rpm just to keep it at 73 miles per hour.

The way back was of course largely downhill, though not completely, and I averaged 54 mpg. I maintained 80-87 miles per hour during this; no point in slowing down when I'm using no gas anyway. There was a roadblock at one point so I had to stop, crawl, then eventually accelerate back up to speed. The battery quickly reached capacity so it wouldn't turn regeneration on even on the level areas like it often does. Even when I braked, a single bar of regeneration turned on. It was really nice gliding along, like when the engine is cold and it doesn't use regeneration then either.

So the average was 43-44. I found it surprising since I'd think doing alot of climbing, even with the downhill freefall, would take more energy than going on level surfaces and I don't get 44 mpg on them. But it's possible the lack of regeneration helped during the downhill part. Temperatures were 60-75 degrees, no A/C was used and no cruise control either. Oil level was exactly at the maximum allowed value, though I think that might be a bit too high, and tires were 42/40.