BMW 5 Series (E12)
Engines

Model
Engine
Power
Torque
Years
518
M10 (M118) 4-cyl
66 kW (89 hp) at 5,500 rpm
142 N⋅m (105 lb⋅ft) at 3,500 rpm
1974–1981
520
M10 (M17) 4-cyl
85 kW (114 hp) at 5,800 rpm
162 N⋅m (119 lb⋅ft) at 3,700 rpm
1972–1977
520i
M10 (M64) 4-cyl
92 kW (123 hp) at 5,700 rpm
172 N⋅m (127 lb⋅ft) at 4,350 rpm
1972–1975
520i
M10 (M64) 4-cyl
96 kW (129 hp) at 5,800 rpm
178 N⋅m (131 lb⋅ft) at 4,500 rpm
1975–1977
520/6
M20B20 6-cyl
92 kW (123 hp) at 6,000 rpm
160 N⋅m (118 lb⋅ft) at 4,000 rpm
1976–1981
525
M30B25 6-cyl
107 kW (143 hp) at 6,000 rpm
211 N⋅m (156 lb⋅ft) at 3,700 rpm
1973–1976
525
M30B25 6-cyl
110 kW (148 hp) at 5,800 rpm
208 N⋅m (153 lb⋅ft) at 4,000 rpm
1976–1981
528
M30B28 6-cyl
121 kW (162 hp) at 5,800 rpm
234 N⋅m (173 lb⋅ft) at 4,000 rpm
1974–1976
528
M30B28 6-cyl
125 kW (168 hp) at 5,800 rpm
234 N⋅m (173 lb⋅ft) at 4,000 rpm
1976–1978
528i
M30B28 6-cyl
129 kW (173 hp) at 5,800 rpm
235 N⋅m (173 lb⋅ft) at 4,300 rpm
1977–1978 (US only)
528i
M30B28 6-cyl
126 kW (169 hp) at 5,600 rpm
230 N⋅m (170 lb⋅ft) at 4,500 rpm
1979–1981 (US only)
528i
M30B28 6-cyl
135 kW (181 hp) at 5,800 rpm
235 N⋅m (173 lb⋅ft) at 4,200 rpm
1978–1981
530
M30B30 6-cyl
130 kW (174 hp) at 5,800 rpm
250 N⋅m (184 lb⋅ft) at 3,500 rpm
1975–1978 (South Africa only)
530i
M30B30 6-cyl
131 kW (176 hp) at 5,500 rpm
251 N⋅m (185 lb⋅ft) at 4,500 rpm
1975–1978 (US only)
530 MLE
M30B30 6-cyl
147 kW (197 hp) at 5,800 rpm
251 N⋅m (185 lb⋅ft) at 3,500 rpm
1976 (South Africa only)
533i
M30B32 6-cyl
147 kW (197 hp) at 5,500 rpm
290 N⋅m (214 lb⋅ft) at 4,250 rpm
1979–1981
M535i
M90 6-cyl
160 kW (215 hp) at 5,200 rpm
310 N⋅m (229 lb⋅ft) at 4,000 rpm
1979–1981

Question: What is common  between the 525, 528, 530, 530i and 533i models of the BMW 5 Series (E12) ?
Answer: The 525, 528, 530, 530i and 533i models of the BMW 5 Series (E12) were fitted with M30 six-cylinder engines.