I remember when they came out & were touted as a beneficial mileage addition that many of the circuits were geared specifically for increased mileage via better metering. a parts man years later opinionated that they were problematic that there was a design flaw(& this guy was pretty sharp, had alot of experience(as parts men go ) With that being said I have never used one or talked to anyone who has as they never were widespread for some reason but I would definitely use one if I had the opportunity