lowest era in a season by a relief pitcher with at least 30 ip; after 1930

Since 1931, Hal Newhouser has the best ERA by a relief pitcher with 30.0+ innings pitched in a season, with an ERA of 0.29 in 1944.

	NAME	ERA	IP	SEASON	TM	G	W	L	W%	GS	SO	CG	SHO	SV	H	ER	R	HR	BB	HBP	GF	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Hal Newhouser H. Newhouser	0.29	30.2	1944	DET	13	4	2	.667	0	17	0	0	2	18	1	5	0	10	0	10		116	0	4.99	2.93	1.70	0.00	14.7	8.6	0.91	.202	1.47	5.28
2	Kevin Siegrist K. Siegrist	0.45	39.2	2013	STL	45	3	1	.750	0	50	0	0	0	17	2	2	1	18	1	15	1	152	0	11.34	4.08	2.78	0.23	32.9	11.8	0.88	.195	0.45	3.86
3	Arnie Portocarrero A. Portocarrero	0.52	34.1	1957	KCA	16	2	0	1.000	0	15	0	0	0	17	2	3	0	5	1	8	1	124	0	3.93	1.31	3.00	0.00	12.1	4.0	0.64	.165	0.79	4.46
4	Zack Britton Z. Britton	0.54	67.0	2016	BAL	69	2	1	.667	0	74	0	0	47	38	4	7	1	18	0	63	3	254	10	9.94	2.42	4.11	0.13	29.1	7.1	0.84	.230	0.94	5.10
5	Charley Schanz C. Schanz	0.59	30.2	1944	PHN	10	4	0	1.000	0	9	0	0	3	14	2	2	0	8	0	8		115	0	2.64	2.35	1.13	0.00	7.8	7.0	0.72	.143	0.59	4.11
6	Joey Devine J. Devine	0.59	45.2	2008	OAK	42	6	1	.857	0	49	0	0	1	23	3	7	0	15	0	10	2	170	0	9.66	2.96	3.27	0.00	28.8	8.8	0.83	.217	1.38	4.53
7	Fernando Rodney F. Rodney	0.60	74.2	2012	TBR	76	2	2	.500	0	76	0	0	48	43	5	9	2	15	3	65	1	282	4	9.16	1.81	5.07	0.24	27.0	5.3	0.78	.220	1.08	5.18
8	Emmanuel Clase E. Clase	0.61	74.1	2024	CLE	74	4	2	.667	0	66	0	0	47	39	5	10	2	10	2	66	1	270	2	7.99	1.21	6.60	0.24	24.4	3.7	0.66	.195	1.21	4.72
9	Dennis Eckersley D. Eckersley	0.61	73.1	1990	OAK	63	4	2	.667	0	73	0	0	48	41	5	9	2	4	0	61	1	262	0	8.96	0.49	18.25	0.25	27.9	1.5	0.61	.213	1.10	5.03
10	Al Benton A. Benton	0.62	58.0	1949	CLE	29	4	0	1.000	0	14	0	0	10	37	4	5	1	21	0	18		222	0	2.17	3.26	0.67	0.16	6.3	9.5	1.00	.194	0.78	5.74
11	Ricky Horton R. Horton	0.65	41.2	1986	STL	33	1	0	1.000	0	18	0	0	3	24	3	3	2	11	1	12	3	154	0	3.89	2.38	1.64	0.43	11.7	7.1	0.84	.180	0.65	5.18
12	Casey Sadler C. Sadler	0.67	40.1	2021	SEA	42	0	1	.000	0	37	0	0	0	19	3	4	1	10	1	2	0	145	2	8.26	2.23	3.70	0.22	25.5	6.9	0.72	.188	0.89	4.24
13	Hank Aguirre H. Aguirre	0.69	39.0	1968	LAD	25	1	2	.333	0	25	0	0	3	32	3	8	0	13	3	16	3	167	4	5.77	3.00	1.92	0.00	15.0	7.8	1.15	.254	1.85	7.38
14	Ray Searage R. Searage	0.70	38.1	1984	MIL	21	2	1	.667	0	29	0	0	6	20	3	3	0	16	1	16	3	149	1	6.81	3.76	1.81	0.00	19.5	10.7	0.94	.194	0.70	4.70
15	Rob Murphy R. Murphy	0.72	50.1	1986	CIN	34	6	0	1.000	0	36	0	0	1	26	4	4	0	21	0	12	2	195	5	6.44	3.75	1.71	0.00	18.5	10.8	0.93	.188	0.72	4.65
16	Mike Adams M. Adams	0.73	37.0	2009	SDP	37	0	0		0	45	0	0	0	14	3	9	1	8	0	5	1	136	1	10.95	1.95	5.63	0.24	33.1	5.9	0.59	.159	2.19	3.41
17	Jesse Crain J. Crain	0.74	36.2	2013	CWS	38	2	3	.400	0	46	0	0	0	31	3	6	0	11	1	5	1	152	0	11.29	2.70	4.18	0.00	30.3	7.2	1.15	.330	1.47	7.61
18	Larry Sherry L. Sherry	0.74	36.1	1959	LAD	14	5	0	1.000	0	26	0	0	3	21	3	3	0	17	1	10	3	142	0	6.44	4.21	1.53	0.00	18.3	12.0	1.05	.214	0.74	5.20
19	Rich Gossage R. Gossage	0.77	46.2	1981	NYY	32	3	2	.600	0	48	0	0	20	22	4	6	2	14	1	30	1	173	1	9.26	2.70	3.43	0.39	27.7	8.1	0.77	.185	1.16	4.24
20	Cliff Melton C. Melton	0.78	34.2	1941	NYG	20	1	1	.500	0	19	0	0	1	29	3	4	2	10	0	10		139	0	4.93	2.60	1.90	0.52	13.7	7.2	1.13	.250	1.04	7.53
21	Claude Passeau C. Passeau	0.78	34.2	1940	CHC	15	4	1	.800	0	24	0	0	5	24	3	3	1	7	0	13		131	0	6.23	1.82	3.43	0.26	18.3	5.3	0.89	.232	0.78	6.23
22	Carl Hubbell C. Hubbell	0.78	34.2	1933	NYG	12	3	1	.750	0	17	0	0	5	25	3	3	0	7	0	11		133	0	4.41	1.82	2.43	0.00	12.8	5.3	0.92	.229	0.78	6.49
23	Blake Treinen B. Treinen	0.78	80.1	2018	OAK	68	9	2	.818	0	100	0	0	38	46	7	12	2	21	1	58	3	315	6	11.20	2.35	4.76	0.22	31.7	6.7	0.83	.230	1.34	5.15
24	Tom Acker T. Acker	0.81	44.2	1956	CIN	22	1	2	.333	0	34	0	0	1	24	4	5	2	18	2	3	1	176	0	6.85	3.63	1.89	0.40	19.3	10.2	0.94	.183	1.01	4.84
25	Paul Hartzell P. Hartzell	0.81	33.1	1977	CAL	18	2	3	.400	0	15	0	0	4	26	3	3	2	6	0	12	4	127	0	4.05	1.62	2.50	0.54	11.8	4.7	0.96	.231	0.81	7.02