i know that it is suposed to be at 8 degrees. every mechanic i talk to tells me to advance it to 10 and it will save me gas. but when it was off at 6 i got the best gas milage? any sugestions? and should advancing to 10 be better or decreasing better?

The ideal timing depends on the octane rating of your gas. If you have a handbook it should tell you what octane rating the stock timing is set for. If you use a higher rating then you can advance it a couple of degrees. A number of years ago some cars came with an adjuster wheel on the side of the distributor that allowed you to vary the timing a few degrees either way. That was before all the emissions regulations.