Avgas 100LL Vapor Pressure (RVP & True): Chart

What Is the Vapor Pressure of Avgas 100LL?

ASTM D910 requires a Reid vapor pressure (RVP) of 38.0 to 49.0 kPa (5.5 to 7.0 psi) at 37.8 °C (100 °F). Typical batches are 42 to 46 kPa. The true vapor pressure at 37.8 °C is a little higher, about 42 kPa on the CRC curve. It roughly doubles every 20 °C: near 21 kPa at 20 °C, 65 kPa at 50 °C and 104 kPa at 65 °C.

Vapor lock happens when fuel in a line or pump turns to vapor. The hotter the fuel and the lower the pressure, the easier it is. High vapor pressure helps cold starts. Low vapor pressure helps hot weather and high altitude. The spec range is a compromise. See the table below for a rough guide to altitude. It is an estimate from the typical curve, not a vapor lock limit.

Avgas 100LL Vapor Pressure Chart

Avgas 100LL True Vapor Pressure vs Temperature Graph

Red line: CRC Report 530 Fig 20, typical “Av Gas” true vapor pressure, read from the graph (about ±4 %), 5 °C to 92 °C (41 °F to 198 °F). Between read points the curve is a straight line in ln P against 1/T. Y-axis is logarithmic. Blue line: Jet A, Jet A-1 and JP-8, 60 °C to 140 °C (140 °F to 284 °F), same figure.

Black crosses are the ASTM D910 Reid vapor pressure limits (38.0 and 49.0 kPa) at 37.8 °C (100 °F), as printed on supplier sheets (not true vapor pressure). Triangles are supplier typical Reid values at 37.8 °C. The dashed bar at 122 °F is the 60 to 90 kPa range at 50 °C on Shell's safety data sheet.

Data from: CRC Report 530 (1983), DTIC ADA132106, Fig 20 (printed p.46); limits from the ExxonMobil, Eni and TOTAL sheets.

Toggle data sets by clicking the legend.

Avgas 100LL Vapor Pressure Calculator

Degrees (°F):

Degrees (°C):

Avgas pressure (kPa):

Avgas pressure (psia):

Avgas pressure (bar):

Avgas pressure (atm):

Avgas pressure (mmHg):

Jet A (kPa):

Jet A (psia):

Calculator gives true vapor pressure, valid 5 °C to 92 °C (41 °F to 197.6 °F) for avgas and 60 °C to 140 °C (140 °F to 284 °F) for Jet A, from the typical CRC curve. It does not give the Reid value of a given batch. For a batch, use the RVP on its certificate.

Vapor Pressure of Avgas 100LL

Reid vs. True Vapor Pressure

Reid vapor pressure (RVP, ASTM D323 or D5191) is a test result. The fuel is sealed in a bomb with a little air at 37.8 °C (100 °F), and the pressure is read. It is the number printed on the certificate. True vapor pressure (TVP) is the pressure of the vapor in balance with the liquid when almost no vapor has formed. For a blend like gasoline, TVP is a little higher than RVP at the same temperature, and CRC says its Fig 20 curves are “derived from Reid vapour pressure data”. TVP is the number that matters for a fuel tank, line or pump at a given temperature.

About This Data

The curve is the “Av Gas” line in Fig 20 of CRC Report 530 (Coordinating Research Council, 1983). It is a typical curve. It does not name a grade or batch. The chart is linear in 1/T and logarithmic in pressure, so the line is nearly straight. We traced it at 5 °C steps. At 37.8 °C it gives about 42 kPa, which sits inside the 38.0 to 49.0 kPa RVP limit. Z Energy prints a typical RVP of 42 kPa (D323) and Viva prints 45 kPa (D5191). A Hjelmco certificate for the unleaded grade UL91 shows 46.4 kPa (D5191).

Vapor Lock and High Altitude (Plain-Words Guide)

A liquid boils when its vapor pressure reaches the pressure around it. Avgas at sea level (101.3 kPa) reaches that near 65 °C. At 10,000 ft the air pressure is only about 70 kPa and the same typical fuel reaches it near 52 °C. In a pump inlet or a line the pressure can be below ambient, so vapor can form sooner. Vapor lock depends on the fuel system, the pump and the fuel temperature. This page does not predict it. Follow the aircraft manual.

Distillation curve (the light ends set the vapor pressure), avgas general properties, density and weight, and jet fuel properties.

Avgas 100LL True Vapor Pressure vs. Temperature

Temp (°C)	Temp (°F)	Avgas true vapor pressure (kPa)	Avgas (psia)	Jet A (kPa)	Jet A (psia)
5	41.0	11.6	1.68	—	—
10	50.0	14.0	2.03	—	—
15	59.0	17.3	2.51	—	—
20	68.0	21.2	3.07	—	—
25	77.0	26.0	3.77	—	—
30	86.0	31.9	4.63	—	—
35	95.0	37.7	5.47	—	—
40	104.0	46.0	6.67	—	—
45	113.0	55.0	7.98	—	—
50	122.0	65.0	9.43	—	—
55	131.0	76.3	11.07	—	—
60	140.0	89.8	13.02	1.90	0.276
65	149.0	104.4	15.14	2.31	0.335
70	158.0	121.3	17.59	2.80	0.406
75	167.0	140.0	20.31	3.44	0.499
80	176.0	161.1	23.37	4.20	0.609
85	185.0	184.4	26.75	5.03	0.730
90	194.0	212.9	30.88	6.00	0.870
95	203.0	—	—	7.03	1.019
100	212.0	—	—	8.20	1.189
105	221.0	—	—	9.69	1.405
110	230.0	—	—	11.40	1.653
115	239.0	—	—	13.28	1.925
120	248.0	—	—	15.40	2.234
125	257.0	—	—	17.89	2.594
130	266.0	—	—	20.70	3.002
135	275.0	—	—	23.68	3.434
140	284.0	—	—	27.00	3.916

Interpolated from the CRC Fig 20 points below (read from graph, ±4 %), straight in ln P against 1/T between points. psia = kPa × 0.145038. — means the curve has no data there. These are true vapor pressures, not Reid values.

Points Read from CRC Report 530 Fig 20

Temp (°C)	Temp (°F)	Avgas read from graph (kPa)	Jet A read from graph (kPa)
5	41.0	11.6	—
10	50.0	14.0	—
15	59.0	17.3	—
20	68.0	21.2	—
25	77.0	26.0	—
30	86.0	31.9	—
35	95.0	37.7	—
40	104.0	46.0	—
45	113.0	55.0	—
50	122.0	65.0	—
55	131.0	76.3	—
60	140.0	89.8	1.9
65	149.0	104.4	—
70	158.0	121.3	2.8
75	167.0	140.0	—
80	176.0	161.1	4.2
85	185.0	184.4	—
90	194.0	212.9	6.0
100	212.0	—	8.2
110	230.0	—	11.4
120	248.0	—	15.4
130	266.0	—	20.7
140	284.0	—	27.0

Read from the printed graph by tracing the line on a 3× render. Jet A points at 50 °C and below are on the edge of the graph and were not used.

Where the Typical Curve Reaches Ambient Pressure

Altitude (ft)	Ambient pressure (kPa)	Ambient (psia)	Temp where avgas TVP = ambient (°C)	(°F)
0	101.3	14.70	64	147
5,000	84.3	12.23	58	136
8,000	75.3	10.92	55	130
10,000	69.7	10.11	52	126
12,000	64.4	9.35	50	122
14,000	59.5	8.63	47	117

Ambient pressure is from the U.S. Standard Atmosphere 1976 troposphere formula. The temperature is where the typical avgas curve above equals that pressure, found by interpolation. It is where the pure fuel would boil, not a vapor lock threshold. Real fuel systems vapor lock below these temperatures if pressure drops in the line. Your batch can differ by several degrees.

Specification Limits for Reid Vapor Pressure

Source	Limit at 37.8 °C (100 °F)	Typical
ASTM D910 as printed by ExxonMobil, Eni, TOTAL	38.0 min / 49.0 max kPa (5.5 to 7.0 psi)	—
CRC Report 530 Table 1 (1981 edition of D910)	5.5 to 7.0 psi (38.5 to 49.0 kPa)	—
Z Energy TDS (2016)	—	42 kPa (D323)
Viva Energy (2019)	—	45 kPa (D5191)
Shell safety data sheet (2026)	38 to 49 kPa at 38 °C; 60 to 90 kPa at 50 °C (method not stated)	—

CRC Table 1 prints 5.5 to 7.0 psi with 38.5 kPa as the converted low limit. Current sheets print 38.0 kPa.

Sources

Coordinating Research Council, Aviation Fuel Properties (Handbook of Aviation Fuel Properties), CRC Report No. 530, 1983. DTIC ADA132106. apps.dtic.mil/sti/pdfs/ADA132106.pdf. Fig 20 (vapor pressure of aircraft fuels, Av Gas and Jet A); Table 1 (aviation gasoline specifications, 1981 D910); section 2.4.2 (true vapor pressure). Values read from the printed graph; accessed 25 Oct 2026.
ExxonMobil, Avgas Series product page (Avgas 100LL limits). mobil.com. Vapour pressure 38.0 min / 49.0 max kPa.
eni, Avgas 100 LL Technical Data Sheet EN101-01, 06/2016. oilproducts.eni.com. Vapour pressure 38.0 to 49.0 kPa (D323, D5190, D5191).
TOTAL Deutschland GmbH, AVGAS 100 LL Produktspezifikation für die Luftfahrt, valid from Oct 2013. content-center.totalenergies.com. Reid vapor pressure at 37.8 °C 5.5 (38.0) to 7.0 (49.0) psi (kPa).
Z Energy, Avgas 100LL Technical Data Sheet, 4 Aug 2016. z.co.nz Avgas-100LL-TDS.pdf. Typical RVP 42 kPa.
Viva Energy Australia, Avgas 100LL, Piston Engine Aircraft Fuel, Oct 2019. vivaenergy.com.au. Typical vapor pressure 45 kPa.
Shell Trading (US), Safety Data Sheet AVGAS 100LL, version 14.0, 6 Sep 2026. epc.shell.com. Vapour pressure 38 to 49 kPa at 38 °C and 60 to 90 kPa at 50 °C.
Hjelmco Oil AB, Certificate of Quality, AVGAS 91/96 UL, batch 095/2021. hjelmco.com. UL91 batch DVPE 46.4 kPa.
ICAO / NOAA, U.S. Standard Atmosphere, 1976, NOAA-S/T 76-1562. Ambient pressure at altitude (formula; the document was not opened for this page).

The CRC curve is a typical curve read from a printed graph, not a measurement made for this site. ASTM D910 was not opened; its limits are cited from CRC Table 1 and the supplier sheets.

Avgas 100LL Vapor Pressure

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