Im contemplating switching my 2006 accent over to synthetic at its 45,000 oil change. I have been changing the pennzoil 5-20/5-30 every 3750K miles (half of the manufacturers recommended 7500 interval). It's mainly a commuter, about 80 miles of freeway per day. I would like to be able to go the whole 7500mi between changes. What 5-20/30 would be a good synthetic for the hot summer and 7500 mi intervals?