So, many of you are still not convinced that you should be using synthetic oil for 7500 mile change intervals in your 4G or 5G Honda Prelude. (Which is what I've done as per the factory service manual for 110k of 120k on the engine.) The images below are (top) an H22A4 valve cover [from a perfectly working engine]with 70,000 miles on it, and (bottom) an H22A4 valve cover from my ride with 120,000 miles on it. I decided to post the graphical difference as seeing is believing. I've taken part in cylinder head work in about 6 H22A4 engines at this point... and all of the synthetic lube users have clean valve covers, and the dino (veggie really) lubed H22A4 are covered in gum, varnish, and sludge. Use synthetics... they work better.