First Trip of 99.9+ MPG

March-April, we drove from Northern Maine to D.C. one day. Then from D.C. to Kansas the next day and thru that night. We stayed there for three days, then returned to D.C. and then to Maine. A total of 4,100 miles round-trip. We saw two tanks that came in at 62mpg. The rest ran from 54 to 58mpg.

 

Only about a mile. The gas station's a mile from here and it's a slight slope down from there.

 

Can you quantify just how flat it must be? Prius' mpg is highly sensitive to elevation change.

My personal goal is to achieve 99.9 mpg for 99.9+ miles, but it won't be flat. Best so far is 99.9 mpg for just over 80 miles, but over more descent than will fit your rules. Best substantial round trip (i.e. exactly zero net elevation change and no net tailwind) is about 71 miles at 72 mpg, but that was under less than ideal conditions, including more than 3000 feet gross climb.

Many competitors have beaten 99.9 mpg over lengthy round trip courses, and not just Wayne Gerdes. If you really want an aspirational target, how about 118 mpg for 1889 miles, on a single tank. Or see this list of previous records. But it would be nice to see what fellow mortals here can do.

 

100 mpg is about 128 wh/mile of energy shaft to wheels.
3 meter drop is about 1470*9.8*3 = 12 wh

So that drop at 100 mpg would be 91.4* mpg on level ground

* 12,800 wh per gallon / 140 wh per mile

 

Using a different method from SageBrush's calculation, but with a very similar result (experience finds that 1 gallon of gas = 10,000 feet of elevation in a 'typical' Prius, though this varies significantly with load and other conditions), I figure that 90.8 mpg on level ground should peg the display to 99.9 on a downslope of 10 feet per mile.

The 2010-12 Prius has a CAFE rating slightly about 70 mpg, and drivers with warmed up engines, driving similarly to the test profile, should be able to match this on level ground without hypermiling. (Most Americans drive faster and much more aggressively, which is why EPA ratings are now heavily discounted from CAFE.) On the same 10-foot-per-mile downslope, with a 70 mpg flatland style, the Prius mpg should rise just above 75 mpg.

These figures should illustrate just how sensitive Prius is to elevation changes.

 

I imagine as long as your "trip" is mostly downhill, 99.9 is easily achievable. It's the trip back...

 

Actually you dis get one taker, me. This is NJ and one mile is about it.

 

i never got more than a mile in my 08.

 

My best so far:


Elevation change ~5000 feet, most of it wasted on B-mode engine braking.

 

151 mpg over 10 miles (20 minutes) on March 9 2011 as registered by my ScangaugeII xgauge AVG display (I use this as my trip mpg display).

It was going from the Toyota DarCar Dealership in Silver Spring MD to the Bethesda MetroRail station (Bethesda, MD) right after a oil change so the car was pre warmed up from the oil change. Surprising I was driving in the morning rush hour traffic swapping between DWB, DWL, and P&G almost all the way going between 25 mph to 35mph on the right hand lane. Tires are at 50 psi front and 48 psi rear. IIRC the vehicle had 100% grill blocking at the time. I can't figure out how to insert a photo into this posting so I've provided a link below with a photo of the display.

Flickr: drydem's Photostream

 

Why not use a round-trip? Then elevation is subtracted from the process.

 

There are quite a few hills and valleys between the two points. A downhill might drop 50 feet but afterward I would have a 50 feet climb uphill. I believe the elevation of the starting point (CherryHill Rd, Silver Spring,MD) and destination point (Downtown Bethesda, MD) was about the same. I was aggressively accelerated downhill as much as I could to build up momentum before going uphill - but because of the traffic - my top speed was between 25 mph to 35mph. Since the starting point was from a Toyota dealership - it was not part of simple commuter route and hence not part of a roundtrip scenario. I have not been able to duplicate this kind of result - I consider it sort of like a fluke/non-repeatable event.