2015 mazda cx-5, 156k miles. Running fine. Only service done are scheduled oil changes, serp belt and rear brakes replaced.
What other service should I do...thinking of new spark plugs, transmission and rear diff fluid. Thanks.

 

At 150K+ miles, I would certainly check the following on my own vehicle, particularly if certain items had never been previously replaced:

• Spark plugs
• Battery
• Fuel filter
• Engine air filter
• Cabin air filter
• Throttle body and MAF sensor cleaning
• Chassis/body bolts, re-torque
• Lube of all hinges
• Fluid in transmission, diff, transfer case
• Hoses in the engine bay and through firewall
• Radiator flush
• Radiator cap
• Tie rod ends, boots
• Ball joints
• Shocks, mounts, boots
• Suspension bushings (check)
• Engine mounts (check)
• Bolts for suspension, re-torque any that have loosened
• Bolts for steering, re-torque any that have loosened
• Water pump, gasket, o-ring -- if have never yet replaced, consider it given the age and typical service life of such devices

At least IMO, at 150K miles many of these things will have seen a good amount of usage and time in service, so it would be worth checking. Worth being even more critical, if your car has experienced "severe" driving conditions. Much of this won't "need" doing, but IMO it's worth checking them.

You might scan the recommended maintenance schedule (tables), for your car. Go through each of the items and consider if any of the "R" (replacement) recommendations have been missed, and if each would be worth checking. For each of the "I" (inspect) items, consider verifying condition (ie, stuff like filters).

 

Big thanks, GAsierra. I'll be doing the check list!

 

You can, of course, break this down and do some chores together like transmission differential and transfer case.
A reliable alignment shop should be able to inspect tie rod ends, other steering gear, etc..
Radiator and thermostat.
Regular tune up items like plugs filters, belt(s), etc..
And so on.

My 2¢

 

good idea!