The only use I found in 89 over 87 at least in my area is the winter bend. Seems my Jeep runs better and gets a little better fuel mileage during the winter months with 89 and go back to 87 in the Spring.
__________________ 2010 Dark Charcoal Pearl Jeep Wrangler Sport S Automatic
4.88 Yukon w/Trac-Lok rear and Eaton ELocker Front - Synergy Gussets - B&M 70264 Trans Cooler
BDS 3" lift - BDS Fox 2.0 Racing Shocks
XHD front Bumper - Trektop NX - Goodyear MT/R w/Kevlar 35X12.5X15 on MB Chaos 5 Wheels - Thrush Turbo Muffler