The Pittsburgh Pirates had the highest run differential by a team in 1991, with a differential of 136 runs.

	TEAM	DIFF	SEASON	G	W%	W	L	AB	R	H	2B	3B	HR	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	Pirates	136	1991	162	.605	98	64	5,449	768	1,433	259	50	126	725	620	35	901	124	46	6,269	2,170	435	99	66	62	111	.263	.338	.398	.737
2	Twins	124	1991	162	.586	95	67	5,556	776	1,557	270	42	140	733	526	40	747	107	68	6,215	2,331	452	44	49	38	157	.280	.344	.420	.764
3	Braves	105	1991	162	.580	94	68	5,456	749	1,407	255	30	141	704	563	32	906	165	76	6,182	2,145	426	86	45	55	104	.258	.328	.393	.722
4	Dodgers	100	1991	162	.574	93	69	5,408	665	1,366	191	29	108	605	583	28	957	126	68	6,159	1,939	328	94	46	50	109	.253	.326	.359	.685
5	White Sox	77	1991	162	.537	87	75	5,594	758	1,464	226	39	139	722	610	37	896	134	74	6,358	2,185	404	76	41	45	132	.262	.336	.391	.727
6	Blue Jays	62	1991	162	.562	91	71	5,489	684	1,412	295	45	133	649	499	58	1,043	148	53	6,167	2,196	473	56	65	49	108	.257	.322	.400	.722
7	Brewers	55	1991	162	.512	83	79	5,611	799	1,523	247	53	116	750	556	23	802	106	68	6,308	2,224	416	52	66	48	137	.271	.336	.396	.732
8	Mariners	28	1991	162	.512	83	79	5,494	702	1,400	268	29	126	665	588	37	811	97	44	6,236	2,104	423	55	62	57	139	.255	.328	.383	.711
9	Tigers	23	1991	162	.519	84	78	5,547	817	1,372	259	26	209	778	699	31	1,185	109	47	6,359	2,310	494	38	44	40	90	.247	.333	.416	.749
10	Red Sox	19	1991	162	.519	84	78	5,530	731	1,486	305	25	126	691	593	32	820	59	39	6,256	2,219	456	50	51	49	143	.269	.340	.401	.741
11	Rangers	15	1991	162	.525	85	77	5,703	829	1,539	288	31	177	774	596	42	1,039	102	50	6,441	2,420	496	59	41	51	128	.270	.341	.424	.765
12	Royals	5	1991	162	.506	82	80	5,584	727	1,475	290	41	117	689	523	35	969	119	68	6,242	2,198	448	53	47	47	126	.264	.328	.394	.722
13	Angels	4	1991	162	.500	81	81	5,470	653	1,396	245	29	115	607	448	38	928	94	56	6,050	2,044	389	63	31	28	114	.255	.314	.374	.688
14	Cardinals	3	1991	162	.519	84	78	5,362	651	1,366	239	53	68	599	532	21	857	202	110	6,020	1,915	360	58	47	48	94	.255	.322	.357	.679
15	Reds	-2	1991	162	.457	74	88	5,501	689	1,419	250	27	164	654	488	32	1,006	124	56	6,134	2,215	441	72	41	54	85	.258	.320	.403	.723
16	Mets	-6	1991	161	.478	77	84	5,359	640	1,305	250	24	117	605	578	27	789	153	70	6,076	1,954	391	60	52	53	97	.244	.317	.365	.682
17	Padres	-10	1991	162	.519	84	78	5,408	636	1,321	204	36	121	591	501	32	1,069	101	64	6,057	1,960	361	78	38	60	122	.244	.310	.362	.673
18	Athletics	-16	1991	162	.519	84	78	5,410	760	1,342	246	19	159	716	642	50	981	151	64	6,192	2,103	424	41	49	55	131	.248	.331	.389	.719
19	Cubs	-39	1991	160	.481	77	83	5,522	695	1,395	232	26	159	654	442	36	879	123	64	6,130	2,156	417	75	55	41	87	.253	.309	.390	.700
20	Giants	-48	1991	162	.463	75	87	5,463	649	1,345	215	48	141	605	471	40	973	95	57	6,097	2,079	404	90	33	59	91	.246	.309	.381	.690
21	Phillies	-51	1991	162	.481	78	84	5,521	629	1,332	248	33	111	590	490	21	1,026	92	30	6,133	1,979	392	52	49	48	114	.241	.303	.358	.662
22	Expos	-76	1991	161	.441	71	90	5,412	579	1,329	236	42	95	536	484	28	1,056	221	100	6,035	1,934	373	64	47	51	97	.246	.308	.357	.666
23	Yankees	-103	1991	162	.438	71	91	5,541	674	1,418	249	19	147	630	473	39	861	109	36	6,140	2,146	415	37	50	38	125	.256	.316	.387	.704
24	Orioles	-110	1991	162	.414	67	95	5,604	686	1,421	256	29	170	660	528	33	974	50	33	6,257	2,245	455	47	45	33	147	.254	.319	.401	.720
25	Astros	-112	1991	162	.401	65	97	5,504	605	1,345	240	43	79	570	502	35	1,027	125	68	6,147	1,908	362	63	43	45	87	.244	.309	.347	.656