I like to see no more than 1 quart consumed between oil changes. Since you should have done 2 oil changes in 6000 miles, your consumption is on the high end of normal. If you are using extended oil change intervals, which is only possible with fully synthetic oil, then max oil consumption should be no more than 1 quart every 3000 miles. Oil can only be leaked or burned, there is no other place for it to go. Check your positive crankcase ventilation system for proper operation and of course, check carefully for oil leaks. Look especially for those leaks that are under pressure, in other words, those leaks that only leak aggressively when the engine is running (such as an oil pressure sender) If leaks are not your problem, then you must be burning it. With compression of 185, I don't suspect rings. You might look at valve guide seals. Look for a blue puff of smoke on start up that immediately goes away when the engine is running.