I just recently noticed that when I change the oil and filter cartridge in my 1967 Camaro SS, after adding 5 quarts the dipstick reads about a half quart low. Is this normal or do I perhaps not have the correct dipstick for the L48 350? The owner's manual states that the engine should take 5 quarts when changing the oil and filter, and 4 quarts when just changing the oil.