7.5 quarts is per the manual. You need to buy at least 4 quarts of 20w50 for the change. This is without an oil cooler, but if you have one, it will not add much if any capacity, because the oil in the cooler will not drain when you drain the sump. Also, if you use a larger filter than stock, take that into account.
MGB
3.3L with oil filter=5 quarts without oil filter=4.5 quarts 3.5L with oil filter=5.5 quarts without oil filter=5 quarts
without oil filter 3.7 quarts with oil filter 4.2 quarts
6.5 quarts
4 quarts without oil filter change, 5 quarts with oil filter change.
For the engine 1.8 need with change the oil filter 4 quarts without the oil filter 3.7 quarts ********************************** For the engine 1.5 need with change the oil filter 3.6 quarts without the oil filter 3.3 quarts
with a new oil filter it is 3.7 quarts with an old oil filter it is 3.5 quarts
with a oil filter change in the 5.3 motor it is 6 quarts with a oil filter change in the 5.3 motor it is 6 quarts
6.9 Quarts with filter
4 1/2 quarts with new oil filter 4 with old oil filter
4.5 quarts with oil/filter change.
4.5 quarts with oil/filter change.