does mpg meter max out at 199.99?

Yes, that is the max displayed. There are many another threads that explains in detail. See 199.9 or True Average for Total MPG Figuring? | PriusChat

 

Toyota did not want to frighten non Prime drivers with the real numbers you can get.

 

The mpg during an engine off glide is usually around 1500mpg. I have seen it as high as 3000+mpg. Trying to make a gauge with that kind of range would be difficult.

 

If the engine is off, the MPG is infinity, by definition.

 

Is that a ScanGauge reading? ScanGauge gives some weird readings when the engine is off, I've actually gotten negative 3000 mpg on my c

 

Somebody needs to tell ScanGauge. Dividing by zero is always problematic.

 

It is a 3.5 digit meter. The first digit is either a 1 or a (blanked out) zero. Cheap.