I had 92k miles on my 97 EX when I switch to Mobil1 10w-30 (used to use regular 5w-30).

My car used to not consume any noticeable amount within 5k miles. After switching, it now consumes about 1/2 qts every 5k miles.

I used to never VTEC before, but after studying more about my car and switching to full synth, I started revving more to 6k-ish to extract power I never used. I haven't recorded to be sure, but I think I burn more oil when I rev more, leading me to think that with gentle revving my car's first 80k miles, I might have stressed the piston rings a bit going into a rev range (due to rod stretch or whatever). Plus, the WOT needed for high revs probably cause more blow by than gentle times.

Anyways, before I switched, I read that sometimes the synthetic can dislodge caked up stuff that was previously helping to seal the engine better.

However, I LOOOVE the way synthetic feels. The engine runs smooth. And if you change your tranny fluid too, your car will feel like new.