imported_flex2003

ok i noticed my car was low on oil, changed it, drove it for over 100km oil was same good to go. drove it for another 500-600km was down 1/2 to 3/4 of a litre, i drove it alittle harder, brought it to 6500rpm one or twice, no oil leaks, when i rev it while idoling, i don't see any burnt oil fumes coming out of exhaust, can anyone help ????it's a 92 civic si with 216,000km, only synthetic oil used...