Which engine? My wife runs a 95 ZJ 70 miles a day commuting. Its got 145K on it, been on Synth since 100k with intervals of 6000 miles. It uses a quart every 3k and is a typical 4.0, it leaks. (hell it leaked before the switch and still leaks
) Overall I'm happy with the switch, saves me having to change the oil monthly.