I know that there are many conditions that can effect the performance of the battery/ICE, but was wondering what top speed people have gotten while driving "in the blue" (on flat roads).
On a flat road in cold NJ, my three week old hits ~41MPH before the ICE kicks in.

 

On flat roads I'd say 41 is about right, but theres a small hill near work, when I go down it I can coast up to 43 or 44 before the ICE reluctantly kicks in.

 

Ive been on battery as high as 43 (maybe 44 tops) but that's really 40 or 41 after you correct for the speedometer's built in 3 miles per hour error. Which is consistent with the theoretical max not overspeeding MG1 (or is it MG2?). Well if you go faster than that without the ICE running you overspeed the MG coupled to the ICE.

 

~40-42 MPH on very flat roads. Seems like it is harder to accomplish when the temps are colder.

 

For me it seems to be exactly 65 KPH. ...which might actually be the intended cutoff point, since the original design uses all metric figures and was converted for the American market.

 

Yup. The Manuals say 64 km/h (~40 miles per hour) as the nominal maximum speed in pure-EV mode, with the ICE stationary. Faster than this, the ICE will need to spin, either under gasoline power or spun by MG1 (the so-called "fuel-cut" mode, which kicks in when coasting at higher speeds — it can be identified by the FE gauge reading precisely 0 L/100 km or precisely 60 mpg).

Stan