I used to own Honda CRX and put 250,000 miles on it. I replaced timing belt and water pump twice but other than that the engine was completely original. From the day I bought it, I kept using Castrol GTX conventional oil. After 250,000 miles, the engine still had within the spec compression. My exprerience is that conventional oil is good enough for our day to day use. Besides, most people don't keep their cars after 100,000 miles or so. If that is the case, what is the reason to use extra expensive synthetic oil?? Well, I now use Mobil 1 on my wife's RAV4 and will use it on my xA starting at the next oil change. To me, synthetic oil is something of "emotional satisfaction". If someone wants to keep a car forever, then the use of synthetic oil makes sense, though.

I used to have a 1989 Honda CRX with 298,000 miles on it and I used Mobil 1 all the time. One time, I hit a metal bar on the freeway that put a big hole in my oil pan. The Mechanic was so amazed on how clean the inside of my engine even with 240,000 mile on it, he was saying it should be full of black or burnt oil in the bottom...he said that synthetic oil really does work.