LSG’s Prius Gas Mileage & Reserve Gas Tank

• Estimating “Empty”
• Gas mileage data

Running average from 0 miles (6/25/07): 46.51 mpg
Running average from 5,300 miles (6/25/07): 46.84 mpg

Estimating "Empty"

In addition to the gas mileage data, the following table also shows how many miles driven after the tank is supposedly empty (Miles after “E”). Here’s what I did. Once the “E” (empty) indicator activated, I reset one of the trip odometers. Then I drove on until some convenient time to refill the tank, while keeping an eye on total miles driven and keeping in mind the Prius’s estimate of gas mileage (mpg). I just want a ballpark figure about how far I can drive on “E.” However, I did run out of gas on March 29, 2004. Click here for the not-so-gory details.

The data suggest that the tank still has about 3 gallons of gas when the gas gauge hits “E.” Given all of this, I can easily drive the car another 100 miles after the gas gauge shows “E.”

By the way, the gas tank supposedly holds 11.9 gals. Three data points are probably enough to divine this information about the capacity of the reserve tank; however, being “anal repulsive,” I’ll be gathering more—across four seasons. There’s some method to my madness. Gas expands in the heat. Because the fuel tank is a soft “bladder” (within a hard container), according to a car salesperson, ya never really know if you’ve filled the gas tank to capacity. P.S. I’m one of those who “tops” off the tank—mostly to the nearest dime in terms of price. However, with this “bladder” gas tank, I’m finding I’m topping off a lot more, and adding a lot more gas after the pump automatically shuts off the first time.

Update, 6/25/07: All right, I’ve been collecting data long enough. It looks like I’m filling the tank every 410 miles (average). A chart of miles between fill-ups shows that I can comfortably drive 450 to 460 miles on a tank of gas. There’s some wiggle room. The real maximum on a tank of gas looks more like 480 miles. After 3.5 years, time to put this theory to test.

Note: Your mileage may vary!

Gas mileage data (Maintenance items not shown.)

Date	Odo	Miles	Amount (gal)	Displayed Mileage (mpg)	Actual Mileage (mpg)	Remarks	Miles after “E”
2007
6/25	47,427	405.7	7.59	52	53.45	70s-80s; Hwy driving R/T Guilderland, NY; A/C
6/21	47,022	246.9	5.053	48.1	48.86	70s: Hwy driving R/T Providence, RI; A/C
6/18	46,775	390	8.53	48	45.72	70s-80s; Local and hwy driving; A/C
6/7	46,385	421.1	9.259	48.1	45.48	70s; Local and hwy driving; A/C	53.1
5/23	45,963	241.7	5.21	45.9	46.39	40s-70s; Local and hwy driving; A/C
5/17	45,772	377.9	7.248	49	52.14	30s-70s; Mostly local driving
5/5	45,344	314.6	6.782	46.6	46.39	30s-70s; Mostly local driving
4/29	45,029	426.1	9.113	46.1	46.76	50s to 70s; to NYC and 2/3rds back	15.8
4/20	44,603	352.6	8.626	43.7	40.88	30s-60s; Local and hwy driving	29.2
4/13	44,250	254	5.944	45.0	42.73	30s-50s; Local and hwy driving
4/6	43,996	336.3	6.632	45.7	50.71	20s-50s; Local and hwy driving
3/29	43,660	419.6	10.013	46.5	41.91	20s-50s; Local and hwy driving	88
3/19	43,240	341.7	8.5	41.3	40.2	20s-40s; Local and hwy driving	8.5
2/13	42,898	394.9	9.263	41.1	42.63	10s-20s; Local and hwy driving	64.8
2/4	42,503	334.5	8.426	43.0	39.7	10s-30s; Local and hwy driving	11.9
1/25	42,169	306.6	7.309	43.6	41.95	20s-30s; Local and hwy driving	0.3
1/17	41,862	323.0	7.231	42.6	44.67	20s-40s; Local and hwy driving	9.4
1/6	41,539	315.0	7.806	44.4	40.35	20s-40s; Local and hwy driving	6
2006
12/30	41,224	236.0	4.98	43.6	47.39	30s-40s; Local and hwy driving
12/18	40,988	422.3	9.21	45.7	45.85	30s-60s; Local and hwy driving	84
12/6	40,566	345.8	8.730	44.2	39.61	30s-60s; Local and hwy driving	18.1
11/22	40,220	233.8	4.251	46.9	55	30s-60s; Local and hwy driving
11/9	39,986	423.1	8.946	47.5	47.29	40s-60s; Local and hwy driving	68.8
11/4	39,563	307.9	7.43	45.1	41.44	40s-60s; Local and hwy driving
10/19	39,255	302.9	6.23	47.4	48.62	40s-70s; Local and hwy driving
10/9	38,952	510.3	11.569	48.5	44.11	From CT; A/C (partial + full tank; 46.7 mpg for last 133 mi.)
10/5	38,442	396.5	5.575	48.4	51.64	To CT (and local CT driving); A/C
9/25	38,154	396.5	8.064	48.3	49.17	Local and hwy driving; A/C
9/15	37,757	445.2	9.007	47.1	49.43	Local and hwy driving; A/C	26.5
9/4	37,312	377.7	8.503	48.1	44.42	From NJ, plus local driving; A/C	9.2
8/28	36,934	372.9	7.575	50.1	49.23	To NJ; A/C
8/16	36,561	423.2	9.071	47.3	46.65	Local and hwy driving; A/C	33.9
7/29	36,138	465.1	9.867	47.3	47.14	Local and hwy driving; A/C	63.7
7/12	35,673	433.9	8.530	49	50.87	From Potsdam, NY; A/C
7/7	35,239	373.9	8.9	47.1	42.01	To Potsdam, NY; A/C
7/4	34,865	434.1	8.007	48.8	54.22	Hwy; A/C
6/27	34,431	469.5	10.287	49.2	45.64	80s; hwy from Guilderland, NY	39.9
6/23	33,961	252.8	5.018	47.9	50.38	80s; hwy to Guilderland, NY
6/16	33,708	362.8	7.677	48.4	38.82	60s to 80s; local and hwy driving
6/12	33,346	425.7	9.677	47.2	50.69	From NJ, plus local driving	51.8
6/5	32,920	352.3	6.95	46.4	43.99	To NJ
5/30	32,567	343.6	8.851	44	47.26	60s to 70s; mostly local driving	13.8
4/11	32,224	385.4	7.279	48.1	52.95	40s to 70s; local and hwy driving
4/19	31,838	366.2	8.615	46.8	42.51	30s to high 60s; local and hwy driving
4/3	31,472	334.1	7.856	45.2	42.53	0 to 50s; mostly local driving	10.9
3/15	31,138	394.2	8.879	47.6	44.4	0 to 40s; local and hwy driving	45.4
3/3	30,744	323.8	7.624	43.1	42.47	0 to 30s; local and hwy driving	11.5
2/10	30,420	382.1	8.496	45.1	44.97	30s to 40s; (fast!) hwy from LI to Nyack, NY, to home+	~30
2/4	30,038	425.8	9.241	46.2	46.08	30s to 40s; hwy to NYC/LI	82.2
2/1	29,612	322	7.865	43	40.94	Below freezing; local and hwy driving
1/14	22,290	364.1	8.483	47.3	42.92	Below freezing; local and hwy driving	12.7
1/5	28,926	333.3	7.729	42.9	43.12	Below freezing; local and hwy driving	30.1
2005
12/21	28,593	353.3	8.378	43	42.17	Freezing; local and hwy driving	69.4
12/5	28,239	345.5	8.077	45.3	42.78	30s to 70s; local and hwy driving	28
11/22	27,894	245.9	5.363	45.6	45.85	40s to 70s; local and hwy driving
11/13	27,648	321.5	7.248	47.6	44.36	40s to 70s; local and hwy driving
11/5	27,326	322.6	6.826	47	47.26	40s to 70s; local and hwy driving
10/21	27,004	361.2	7.64	47.3	47.28	50s to 70s; local and hwy driving	31.6
10/10	26,642	452.3	9.06	54.4	49.92	50s to 70s; local and hwy driving	12
9/26	29,190	487.1	9.531	52.6	51.11	70s and 80s; local and hwy driving; A/C	70.8
9/14	25,703	454.3	7.79	52.8	58.32	Hot (>90s) & humid; hwy & rural hwy driving (MA, coastal NH, ME); A/C
9/2	25,248	399.8	8.65	52	46.22	Hot (>90s) & humid; hwy & rural hwy driving (From Cooperstown; MA); A/C
8/30	24,849	476.7	9.524	51.4	50.05	Hot (>90s) & humid; hwy & rural hwy driving (MA; to Cooperstown); A/C; sta attd filled tank	25.8
8/18	24,372	412.3	8.371	50.3	49.25	Hot (>90s) & humid; hwy & rural hwy driving; A/C	9.5
8/13	23,959	411.3	9.703	52.3	42.39	Hot (>90s) & humid; hwy & rural hwy driving; A/C	54.7
8/9	23,548	495.9	8.337	51.5	59.48	Hot (>90s) & humid; hwy driving; touring; A/C; tank not to “full”	27.0
7/30	23,052	431.5	8.394	51.5	51.41	Hot (>90s) & humid; local and hwy driving; A/C	27.0
7/16	22,621	472.2	9.452	48.3	49.96	Hot (>90s) & humid; local and hwy driving; A/C	19.4
7/9	22,148	457.7	9.756	49.9	46.91	70s through 90s; local and hwy driving; A/C	48.9
6/29	21,691	405.4	8.125	51.1	49.9	Rural hwy driving; R/T Guilderland, NY, across VT; 80s to 90s; A/C
6/24	21,285	374.4	7.205	50.8	51.96	80s and 90s; rural hwy driving; A/C
6/15	20,911	387.1	8.609	45.6	44.96	70s and 80s; local and hwy driving; A/C	15.9
6/9	20,524	485.3	9.765	51.9	49.7	70s and 80s; local and hwy driving; A/C	?
6/1	20,038	449.4	8.731	49.4	51.47	70s and 80s; local and hwy driving; A/C
5/20	19,589	460.6	9.804	49.7	46.98	50s to 70s; some highway driving	53.4
5/7	19,128	379.8	8.0	50.1	47.48	50s to 70s; some highway driving
4/27	18,748	388.1	7.667	50.3	50.62	Days: 30s to 60s; nights: 40s; some highway driving
4/18	18,360	469.5	9.335	50.8	50.29	Days: 30s to 60s; nights: 20s and 30s; some highway driving	67.5
4/4	17,890	428.6	8.851	50.2	48.42	30s to 40s; some highway driving	42.4
3/26	17,462	363.9	7.505	49.5	48.49	30s to 40s; some highway driving
3/16	17,098	379.5	8.813	45.7	43.06	30s to 40s; about half of this is highway driving	45.4
3/4	16,718	306.3	6.797	46.7	45.06	Teens and 20s. Some snow
2/25	16,412	310.8	7.714	44.7	40.29	Well below zero at night; teens during the day. Some snow.	9.6
2/11	16,101	343.3	7.181	46.1	47.81	Well below zero at night; teens during the day. Snow.	0.5
2/2	15,758	333.7	7.601	44.0	43.9	Well below zero at night; teens during the day. Snow.	27.9
1/19	15,424	345.4	8.463	40.9	40.81	Well below zero at night; teens during the day. Snow.	60.4
1/5	15,078	257	5.797	47.5	44.33	Below freezing temperatures. Some snow.
1/1	14,821	310.1	7.188	44.2	43.14	Below freezing temperatures. Some snow.	7.8
2004
12/16	14,511	426.9	9.2	46.3	46.4	Below freezing temperatures	74.9
12/7	14,084	323.6	7.493	45.5	43.19	First snowfall, followed by freezing drizzles	40.6
11/27	13,761	357.0	8.41	45.1	42.45	Getting colder, day (40s) and night (freezing and subfreezing)	72.6
11/23	13,404	306.5	5.953	47.3	51.49	Getting colder, day (40s) and night (freezing and subfreezing)
11/12	13,097	413.3	9.412	45.9	48.62	Subfreezing evenings	63.2
11/1	12,684	397.1	8.168	48.8	43.91	Subfreezing evenings	2.6
10/24	12,287	472.5	9.521	50.2	49.63	Getting cooler, nights and days: 40s to 70s	66.8
9/26	11,814	460.0	9.782	48.5	47.03	Local, some rural/super hwy; A/C. Day temps dropping to the 70s.	59.1
9/18	11,354	432.1	8.433	49.5	51.24	Local, some rural/super hwy; A/C
9/8	10,922	411.8	8.866	48.5	46.45	Local, some rural/super hwy; A/C	11.8
8/21	10,510	423.6	8.481	49.2	49.95	Local, some rural/super hwy; A/C	34.4
8/8	10,086	469.7	10.258	49.9	45.79	Rural/super hwy driving (mostly); mid 80s/mid 90s; A/C	46.7
8/1	9,617	485.7	9.923	51.3	48.95	Rural/super hwy and local driving; high 80s/mid 90s; A/C	79.1
7/24	9,131	516.6	9.273	53.5	55.71	Rural/super hwy and local driving; high 80s; A/C	24.5
7/18	8,614	407.4	8.25		49.38	Mostly Auburn-->NY, across VT; A/C	2.8
7/13	8,207	467.3	9.297	51.5	50.26	Rural (mostly)/super hwy and local driving; ~80º A/C	71.5
7/4	7,739	319.3	7.945	53.8	40.19	Rural/super hwy and local driving; mid 80s; A/C	19.5
7/2	7,420	423.1	6.704	50.4	63.11	Rural/super hwy and local driving; mid 80s; A/C
6/27	6,997	459.6	8.337	52.0	55.13	Rural “hwy” to NY, across VT; upper 70s
6/16	6,537	480.0	10.106	48.3	47.50	Hwy driving. Weather in the 80s; A/C	7.6
6/7	6,057	435.5	10.03	50.3	43.42	Warm weather. Some A/C.	46.8
5/30	5,622	307.8	5.478	50.7	56.19	Warm weather. Some A/C.
5/26	5,314	430.6	10.024	48.1	42.95	Possible mileage: lots of standing around with car on, and A/C	24.2
5/15	4,883	419.5	8.726	48.9	48.07	Decidely 70s, some 80s, two 90+ days (yuk!)
5/8	4,464	467.7	9.726	49.0	48.09	Mostly between 50º and 60º	40.5
4/28	3,996	433.9	9.180	47.9	47.27	Mostly around 45º	58.7
4/9	3,562	425.1	8.746	48.9	48.61	Mostly between 37º and 40º	32.8
4/3	3,137	369.7	8.786	43.3	42.08	37º±4º; lots of hwy driving	17.8
3/29	2,767	487.2	~10.935	46.8	44.55	32º-47º; Ran out of gas!	104.2
3/19	2,280	422.8	10.247	43.0	41.26	Below freezing	71.0
3/8	1,857	454.6	9.586	48.4	47.42	~37º	93.6
2/26	1,402	418.8	9.383	44.7	44.63	Warming still: 37º to ~41º
2/20	984	395.5	9.562	42.3	41.36	Warming! ~30º	48.0
2/5	588	324.7	8.772	39.8	37.02	Cold: <20º	32.3
1/22	263	263	7.895	35.8	33.31	Cold: <20º

Note: The Prius displays overall gas mileage until reset. (I reset the display after each tankful.) Or, your trusty calculator can display the gas mileage by dividing the total miles between tank fillups by the amount of gas to fill the tank. Hence the two columns: “Displayed Mileage (mpg)” and “Actual Mileage (mpg),” respectively. I haven’t figured out why the difference between the two calculations. “Slide rule error”?

Note 2: According to the EPA: 61 mpg city; 51 mpg highway. According to Car and Driver and Consumer Reports: 42 mpg to 44 mpg, respectively.