I have had very good luck with my 1986, 5.0Ltr, FI engine using Quaker State Oil, 10W-30, Semi-synthetic Motor Oil. I have a Jasper Rebuilt engine with 95K Miles on it, but conditions are very good with this oil. I have a Lincoln Continental with a 3.8Ltr, V6 in which I started using this oil, and I did directly notice a difference. My lincoln was equipped with a electronic "MPG" gauge, and when completely switching to the synthetic compound I read at least 1-3 more MPG on the meter. I do a lot of driving and my route was pretty much consistent from one day to the next. Under very similar conditions the synthetic formula returned a increase in MPG, and was measurably cleaner after replacement. I am also using the FRAM HI-Flow Oil Filter with each replacement. I have substituted this setup, and formula on the Bronco.