Hey Randy,
On my tank bibs, side covers and the occassional seat I use: dye > neatsfoot > tankote > Pecard's Motorcycle Leather Lotion > Pecard's motorcycle Weatherproof Dressing (natural or black depending on project colors).
Had my first gasoline test last weekend as reported by a client. He was fooling with his GPS while getting fuel and lifted the nozzle out of the tank tube shooting gas down the tank and tank bib. The above finish resisted the gas long enough for him to simply wipe off at the station, let it air out at home and re-apply/buff it with wax dressing with no ill effects. It's also a two-color fade on the bib and sun, rain and now gasoline haven't bothered it at all after 3 months on the road. Folks that bought my first bibs a little over a year ago report similar results.
Side note - should motorcycle leathers get doused in gasoline, air it out and spray the back with a 50/50 solution of vinegar. Kills the gas smell within 24 hours and it doesn't leave it's own residue or smell. I was able to test and confirm this as well.
Hope this helps,
Chris
P.S. - links to the Pecard stuff I use:
Leather Lotion (they also have smaller sizes): http://www.pecard.co...y_Code=mlotions
Black Weatherproof Dressing: http://www.pecard.co...ry_Code=mwproof
Natural Weatherproof Dressing: http://www.pecard.co...ode=mleathdress