The introduction of the X and Y class diesel-electric locomotives in 1955 meant that construction of fuel oil tank wagons to supply their needs was necessary. The W.A.G.R. met this need by converting existing J class water tankers into fuel oil tankers. The wagons in this class fall into two main groups and there were also three groups of odd wagons. The first group were converted from 1600 gallon J class tankers built on standard GC type 16'-0" wooden underframes. These wagons were converted to class JOA as follows:

No picture of wooden framed JOA available

1955	621, 9607, 10255, 10332, 10376, 10386, 10389, 10402, 10434, 10438, 10455, 10485, 10512, 10560, 10571 from J
1959	1076 from J
1960	8038, 8529, 8863 from J
1961	215, 6646, 6911, 6960, 8421, 8548, 9304, 9790, 10323, 10449, 10522 from J
1963	8399 10362 from J
1964	4893, 6435, 7577, 10266, 10401, 10510 from J
1965	6499, 7447, 8126, 9546, 10242, 10361, 10382 from J

The WAGR outline diagram of the wooden underframe JOA is shown below.

The initial decision to use wooden framed tankers for this job was surprising and after about 15 years these frames (unlike the tanks) were life expired. The solution adopted was to reuse the tanks but fit then to steel chassis recovered from scrapped CXA class sheep wagons. In most cases the "new" wagon used the CXA number but in some instances, rather bizarrely, the number of the tank was used as in the photo opposite. The disposal of the wooden framed wagons took place as follows:

JOA 10560 in later years running as a waste oil wagon.

1960	10434 written off
1964	6911 written off
1968	7447, 8421, 9546, 10389 written off
1970	621, 6435, 6646, 7577, 8126, 8399, 9607, 10323, 10361, 10382, 10438, 10510, 10512, 10522, 10571 written off
1971	1076, 8548, 9304, 9790, 10266, 10332, 10386, 10455 written off
1972	215, 10255, 10401, 10402 written off
1973	4893, 6499, 6960, 8038, 8529, 10242, 10362, 10485 written off 8863, 10376 rebuilt with CXA frame and retained JOA number
1974	10449 written off
1976	10560 rebuilt with CXA12099 frame and retained JOA number

The new steel-framed wagons were based on both W.A.G.R. and M.R.W.A. built CXA class wagons. They came into service as follows:
1967	12051, 40404 from CXA
1968	11312, 12062, 40405, 40428 from CXA
1969	378, 10202, 11321, 11342, 40401, 40417, 40427 from CXA
1970	740, 855, 4019, 10071, 11305, 11324, 40409, 40420, 40423 from CXA
1971	739, 841, 1129, 1229, 1974, 10082, 11331, 40419 from CXA
1972	12087 from CXA
1973	Wooden JOA8863, 10376 rebuilt with CXA frame and retained JOA number
1976	Wooden JOA10560 rebuilt with CXA12099 frame and retained JOA number
1977	8038 from written off JOA tank and CXA frame

The disposal of the steel-framed wagons was rather more drawn out (over 18 years) and started before all of the conversions were completed.

1972	1974 written off
1973	40423 written off
1974	40405 written off
1983	740, 10202, 11312 written off and tanks used for JOB class
1984	40401 converted to class J 378, 739, 841, 855, 1129, 1229, 4019, 10071, 10082, 10376, 11305, 12087, 40404 written off and tanks used for JOB and JOC classes
1985	10560 converted to class J 40409 written off
1986	8038, 11321, 11331, 40419, 40420 written off
1988	8863, 11324, 11342, 12051, 12062, 40417, 40427 written off
1990	40428 written off

In 1965 a further wagon was converted to class JOA but this wagon had a steel GC type frame from the beginning. This wagon (JOA9156) lasted until 1973

The next of the odd wagons were JOA 7102 and 8038 which were fitted with a tank with three wooden bolsters rather than the anchor plates used on the rest of the class  (it is possible that they were others). JOA 7102 was converted from class J in 1960 and lasted until 1968. The tank was then transferred to the chassis of CXA40421 which was eventually written off in 1976. JOA 8038 was originally on a wooden GC type chassis.  The tank was put on a CXA chassis but stayed as 8038 in 1977.  I think that these tanks may have been old J class 1500gallon tanks fitted with new ends to increase the capacity to 1600 gallons.

The final group I am unsure about but may have had standard 15'-0" G type underframes. These were 1078 and 2511 converted from class J in 1961. They lasted until 1964 (2511) and 1968 (1078) respectively.