I'm going with Mustanguy on this, too. I've used the CD-2 oil detergent with very good results. Start out with a fresh oil & filter change (I'm using 10W-30, that's the highest viscosity I'd recommend to anyone) and put the CD-2 in. That stuff will turn your oil black within 1000 miles, maybe less. That's normal, since it's just detergent, and it's cleaning and suspending dirt & crud. Change it all again in 1000 miles, and if it still has a lifter problem, repeat with the CD-2. If you want to change over to synthetic oil, by all means, go for it. You'll run cooler and longer between oil changes, and your engine will probably run smoother. Hope this helps.
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Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch 
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