315,000 on truck (unknown if the engine was ever replaced) has front crank/cam seal leak, maybe distributor leak too (to damn dirty under the hood from 4x4in and the front oil leak)
airfilter changed 10,000 km ago
fuel filter is sitting in my toolbox... havent done it since 288,000 (when i bought it)
havent done any checking of vac lines or ignition
just had synthetic 75w90 thrown into the trans, transfercase, and dyno 80w90 in the diffs. less then 10,000 ago
235/75r15's on it, unknown psi (shop did them, runs nice down the road...) but it had better gas mileage with these tires before (so i dont think the tires are the problem)
Not to doubt your personal maintenance schedule, but my Chilton's says on a fuel injected engine to replace the fuel filter every 30,000 miles or 30 months, whichever comes first. Just throwin it out there
thats as a maximum, alot of guys change it out earlier because if poor gas quality or just it being an older vehicle (tank starting to rust and such)