I've been running mobile 1 synth since the truck was new and I change it every 5k mi. They say you can run it 10K, but I think it's worth it to change it every 5 IMO. I normally change synth every 5K and dino oil every 3K (what I ran in previous older cars I owned).
2004 Tacoma TRD 4x4 V6 5spd Xtra cab
265/75R16 BFG AT ko, Deck plate mod w/ K&N, custom grey wire mod, breathers extended, Scan Gauge II, back-up lights, clear corners and red/clear tails, spray-on bed liner, custom stereo system installed and built by me with Alpine, MTX, Audiobahn, etc.