Double Tank Mileage Contest

I was unaware. That is very good to know, and nicely explains the grouped biases in fuel economy inaccuracy reported in the forum. Thanks

 

Announcement

I'm game for the 500 mile stunt
Stock Prius v(agon) 20 months old, 54k miles on the odometer. OEM tyres at sidewall max pressure

Geography: SW Colorado, about 6000 ft elevation with gently rolling hills
Strategy: Either next week or the week thereafter I have a 5 day window I don't have to drive highway speeds. I'll drive ~ 100 miles a day split into two sessions of ~ 50 miles each. The route is mixed residential and rural, 8 miles each way, 95+% below 45 mph and "P&Gable."

PENDING:
10 mile drive to calibrate distance meter
32 mile drive later today to check that my fuel economy is within spitting distance of the double-EPA goal

 

I started out too late in the evening, so I only drove 16 miles.



I'm reasonably happy with the result, although it includes a couple of items for and against:

1. 2-3 bars of battery SOC were lost from start to finish (negative)
2. The car had a bit of warm-up before I took off as I looked for an open door. I zeroed the meter just before I started to roll (negative)
3. I expect the actual MPG to be about 5% lower after distance calibration (negative)
4. Headlights were on (positive since I will not use them in daily driving. ~ cancels (3)
5. My technique was sub-optimal (positive I hope)
6. 3/4 of my 16 mile routes will be with a pre-warmed engine (positive, more than cancels (2)

So all in all the trial run confirms that 84 MPG is reachable, and I hope for a bit more. 90 MPG seems out of reach. An aside: I've picked my route because it does not have much traffic and so brake use is minimal and I can coast to STOP signs. OTOH, the roads are rather poorly maintained and bumpy, so fuel economy in the mid- high 80s is I think quite an achievement for a Station Wagon

 

I started a run yesterday -- 64 miles. I have a 9 day vacation so I'll likely finish off 600 miles to get into the record book. 1000 miles is too much work for my lazy self. Note that the numbers in this table are PRE correction for display inaccuracy. I'll calibrate by mileage markers at the end of the marathon.

	Date	am/pm	CUM MPG	Odometer	Trip MPG	Temperature (F)	Day MPG
1	10/2/2014	am	81	16	81.00	63
2			85	32	89.42
3			85	48	85.00
4			86	64	89.15		86

 

After a 2 day hiatus, I sat my butt down and drove for 4 hours. That really is my limit -- T-shirt or not.
The first 16 miles were (relatively) terrible, so I spent the rest of the afternoon clawing it back. I was worried that today's wind would be my undoing but it either did not matter, or the wind was offset by a warmer day. I tend to think the latter is true.

Today I parked in a part of my driveway where the sun tomorrow will not be shaded; and I might 'cheat' a bit by opening the hood an hour or two before my drive to 'pre-heat' the engine.

	Date	am/pm	CUM MPG	Odometer	Trip MPG	Temperature (F)	Day MPG
1	10/2/2014	am	81	16	81.00	63
2			85	32	89.42
3			85	48	85.00
4			86	64	89.15		86
5	10/5/2014	pm	83.7	80	75.61	68 - 74
6			84	96	85.53
7			84.5	112	87.63
8			85	128	88.67
9			85.1	144	85.91
10			85.6	160	90.38
11			86	176	90.22
12			86.3	192	89.74		86.4

 

For gen 2 Prius 2X EPA would be 92 MPG. During the 3 summers when I had the leisure to commute via back roads at speeds between 25 and 40 MPH, there was only one tank that by chance (noise) went above 90 MPG (real calculated MPG, not MFD MPG which is too optimistic as shown in the data below). Now I no long have the leisure but even if I did, it would be hard to achieve - for me at least.

 

Yes if one could afford the time to drive around at 20 MPH then it is easily achieved. Best wishes to all contestants.

 

I'm trying to reconcile that with the requirement to drive 1904 kilometers (1190 miles) without refueling. Why not just set a target around 800 km's (500 miles)?

 

My average speed starts fresh every time I shut down the engine, but the times I have looked I have seen 29 mph. I'm not saying that is optimum, only that it is ~ consistent with being competitive in the challenge.

 

Another day at the wheel; my wife is giving me funny looks.
Once again, the first 16 miles drops the average quite a bit, and I spend the rest of the day getting it back. Today was warmer than yesterday, the car was in the sun, AND I popped the hood for sun engine sun-bathing two hours before I took off. What can I say -- the warm-up penalty is hard to avoid. Pre-calibrated MPG is now 86.7 after 302 miles, up from 86.3 yesterday.

Since the inline table is getting too long, here is a link to the table as a Google sheet. Below is the data in a pretty graph.

 

Refuel all you want, just do not reset the trip meter.

 

The Toyota block heater will help some. With 2 hour use, and ambient temps around 20C you'll start off with coolant temp around 40C, climbing to 50C within a block or two, once it homogenizes. Obviously the engine itself is warming, but the BH does jumpstart the process.

 

That would really be cheating, but outside of this competition it is a good idea. And now that I think of it, I probably should have attached my scangauge for temperature monitoring and blocked the engine radiator air intake vents.