Findings

What 301 tanks say

Nothing on this page is typed in. Every number is computed from the log when the site builds, so it moves the moment a tank is added. Averages that would rest on fewer than 5 tanks are left blank rather than stated.

The price of a gallon, 2013 to 2026

Total paid divided by gallons pumped, one dot per fill-up, colored by car. Diesel for the Golf, regular gasoline for the rest.

$1.53

Cheapest gallon

May 19, 2020, 2017 Honda Fit

$4.46

Priciest gallon

June 30, 2022, 2017 Honda Fit

$1.98

Cheapest year

2020 average over 22 tanks

$3.89

Priciest year

2013 average over 27 tanks

$2.88

All-time average

mean of 301 tanks; $2.93 as total dollars over total gallons

Price by month

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
2013	4.00	4.08	4.00	3.85	3.80	3.80	3.85	3.90	3.90	3.90	3.90	3.84
2014	3.70	3.73	3.85	3.85	3.83	3.72	3.67	3.66	3.59	3.49	3.32	3.18
2015	2.60	2.76	2.65	2.60	2.77	2.66	2.61	2.55	2.43	2.40	2.39	2.28
2016	2.06	1.90	1.98	2.09	2.23	2.36	2.28	2.28	2.30	2.31	2.34	2.40
2017	2.29	2.51	2.37	2.21	2.21	2.14	2.16	2.25	2.70	2.39	2.42	2.28
2018	2.46	2.37	2.44	2.56	2.72	2.71	2.69	2.72	2.75	2.78	3.06	2.00
2019	2.07	2.11	2.29	2.70	2.64	2.46	2.55	2.40	2.53	2.46		2.35
2020	2.31	2.13	1.99		1.53	1.90	1.96	1.97	1.96	1.97	1.98	1.96
2021	2.15	2.24	2.64	2.61	2.52	2.89	2.93	2.98	2.95	3.10	3.19	3.12
2022	3.14	3.32	4.24	3.93	3.92	4.46	4.20	3.54	3.30	3.22	3.14	2.88
2023	3.00	3.30	3.26	3.22	3.29	3.22	3.27	3.99	3.38	3.07	2.80	2.99
2024	2.75	2.94	3.33	3.41	3.39		4.11	2.94		2.47	2.90	2.91
2025	2.97	3.14	3.06	3.15	2.99		2.82	2.98		2.87	2.72	2.82
2026	2.56	2.66	3.45	3.65	3.94	3.55	3.70	3.80	3.92

$1.53 $4.46 average price per gallon in that month; brighter is pricier; diesel through early 2017

January

Cheapest month of the year

$2.67 average over 26 tanks since 2013

May

Priciest month of the year

$3.04 average over 26 tanks

Every tank since 2013 grouped by calendar month, all years together. The gap between the two months is what seasonal blending and summer demand look like from one household's receipts.

How much driving

Miles logged in the year divided by the days those tanks covered. The first tank of each car counts its days from the purchase date.

41.0 miles a day in 2014, 11.0 in 2024

The busiest and quietest full years in the log. The slide starts in 2016, the year the notes record a new job.

51 days without a fill-up in spring 2020

The longest gap of that year ended May 19, 2020, at $1.53 a gallon. The pandemic shows up in a fuel log as silence.

Habits

Saturday is the most common fill-up day (51 tanks); Tuesday the least (35). Counted from the date of every tank in the log.

What it costs

Dollars spent on fuel per calendar year, every car combined.

Fuel cost per mile over each car's whole record: total dollars divided by total miles. Fuel only; no maintenance, insurance or depreciation.

Mileage

Mean of the per-tank MPG figures for each car. Hover a bar for the overall miles-per-gallon ratio, which weights big tanks more.

42.1MPG

Best tank ever

2012 Volkswagen Golf TDI, October 21, 2013, 533 miles (Ultra conservative driving habits)

28.1MPG

Worst tank

2013 Honda Fit, May 24, 2017

533mi

Longest tank

2012 Volkswagen Golf TDI, October 21, 2013

13.84gal

Biggest fill

2012 Volkswagen Golf TDI, December 21, 2016

$53.09

Priciest fill

2012 Volkswagen Golf TDI, October 4, 2013

52days

Longest gap

ending July 12, 2024, 2023 Toyota Corolla

Temperature and mileage

Each tank against the mean temperature over the days it was driven, measured at Atlanta. One panel per car, because every car has its own MPG baseline; the dashed line is a straight fit.

+0.2 MPG per 10°F, a small effect

The fitted slopes averaged across cars, weighted by tank count. It is not the same car to car: the 2023 Toyota Corolla moves the most at +0.6 MPG per 10°F, the 2012 Volkswagen Golf TDI barely at all at +0.1. Temperature explains at most 12% of the tank-to-tank variation in any car; trips, traffic and how full the tank was matter more.

2012 Volkswagen Golf TDI

100 tanks. Fitted: +0.1 MPG per 10°F, r = 0.08.

2013 Honda Fit

78 tanks. Fitted: -0.3 MPG per 10°F, r = -0.23.

2017 Honda Fit

72 tanks. Fitted: +0.4 MPG per 10°F, r = 0.25.

2023 Toyota Corolla

51 tanks. Fitted: +0.6 MPG per 10°F, r = 0.35.

Car	Cold, under 50°F	Mild, 50 to 75°F	Warm, over 75°F
2012 Volkswagen Golf TDI	36.5 (27)	37.2 (52)	36.8 (21)
2013 Honda Fit	31.2 (14)	30.4 (43)	30.2 (21)
2017 Honda Fit	33.5 (19)	34.7 (40)	35.0 (13)
2023 Toyota Corolla	31.9 (12)	33.6 (26)	34.4 (13)

Average tank MPG by temperature band, tank counts in parentheses, blank under 5 tanks. A tank's temperature is the mean of the daily means from the day after the previous fill through the fill day, and needs 80% of those days on record. Weather data by Open-Meteo (ERA5 reanalysis, Atlanta grid point), 100% of tanks covered.

Seasons

Car	Winter	Spring	Summer	Fall
2012 Volkswagen Golf TDI	36.4 (27)	36.8 (26)	36.8 (25)	37.9 (22)
2013 Honda Fit	31.1 (15)	30.5 (21)	30.0 (24)	30.5 (18)
2017 Honda Fit	33.5 (22)	34.4 (18)	34.8 (16)	35.3 (16)
2023 Toyota Corolla	32.0 (13)	33.7 (13)	34.7 (15)	32.9 (10)

Average tank MPG by season, with the tank count in parentheses. Winter is December to February. A cell shows only the count when a season has fewer than 5 tanks for that car. The old notes column already suspected this: "Winter Storm" and "Hot > 90" sit next to tanks in 2014 and 2016.

Year by year, every car

Year	Fill-ups	Miles	Gallons	Spent	Avg MPG	Avg $ / gal	Cost / mile	Miles / day
2013	27	12,902	348.3	$1,355	37.0	$3.89	$0.105	36.0
2014	30	14,564	386.8	$1,415	37.6	$3.66	$0.097	41.0
2015	23	11,490	301.7	$774	38.1	$2.57	$0.067	31.5
2016	18	8,166	236.1	$520	34.6	$2.20	$0.064	22.3
2017	31	7,962	255.9	$594	31.0	$2.32	$0.075	21.8
2018	27	6,974	229.0	$594	30.5	$2.59	$0.085	19.6
2019	24	6,109	202.3	$487	30.2	$2.40	$0.080	17.7
2020	22	5,945	171.5	$340	34.7	$1.98	$0.057	16.4
2021	23	6,052	178.9	$498	33.9	$2.78	$0.082	16.5
2022	19	5,089	146.5	$514	34.8	$3.50	$0.101	13.9
2023	17	5,211	146.7	$477	35.6	$3.27	$0.092	14.5
2024	13	3,901	117.0	$367	33.4	$3.14	$0.094	11.0
2025	15	4,439	141.0	$412	31.5	$2.92	$0.093	12.2
2026	12	3,505	103.8	$355	33.7	$3.40	$0.101	13.0