Okay, the early and mid cycle P2 cars (early to mid 2000s) are making their way through 100-200k now. So what should you expect? How do you maintain it depending on your skill level.
My car is at 132k mi and 116k mi so I'm not quite at 200k yet. Here is what you can expect
Worn suspension components will cost good money if you can't DIY. I would guess front+rear suspension refresh would cost $2500 all together at a shop. DIY will cost you perhaps $600-700 in parts.
Beyond the guaranteed worn parts, there will be failures, in terms of maintenance, the failures can be summed up in 3 general categories
There will be a few of electronics module and sensor failures going forward. There are usually no signs of impending failure so there isn't anything you can do but relax :) If you can't DIY, new parts are typically expensive along with the high labor prices. DIYers need to invest in the VIDA/DiCE diagnostic tool for diagnoses and can find lots of used parts are available on ebay + recyclers for much cheaper.
Mechanical parts usually fail gradually. The failing parts that are visible to inspection can be caught early during inspections. Non DIYer might consider taking the car into dealer for regular oil changes. It is in their best interest to fully inspect your car and call out failures to generate business :) So think of it as a free inspection 2-3 times a year. DIYers may want to do this as well just to get a pair of trained eyes to inspect the car periodically. After 100k miles, you can expect a few of mechanicals to fail on your way towards 200k miles. Again, Non DIYers will pay good money while DIYer can gain good savings.
There are mechanical parts that are nested deep inside that can not be easily seen during a routine inspection. These require performing special diagnostics to evaluate the sign of health. Think of it as a blood test, blood pressure, taking the pulse rate for the car. A few of key ones are to check for PCV system blockage, engine compression test, and sending oil in for analysis.
Here is a good maintenance schedule to follow. Note that Volvo doesn't suggest some of these but they really should. I think they simply didn't know some of the wear items when they published the maintenance guide.
1k check your engine oil. Higher mileage may encounter oil leak or consumption. Catch it before too late
5k synth oil change (use synth, it will keep your PCV system healthier)
15k cabin air filter
30k plugs
air filter
coolant flush+thermostat
ATF flush or drain+fill (D+F is easy and sufficient if kept up. Basically replace about 50% of the ATF)
upper motor mount. Read this
50k clean throttle body, clean MAF
75k front suspension (strut, LCA bushing, spring seat, end links)
rear suspension (shock, end links)
steering (tie rods, PS flush)
drive line (AWD: angle gear fluid, rear diff fluid)
fuel filter
100k timing belt (including tensioner and roller)
serpentine belt
brakes 1 rotor will last 2 sets of brake pad changes
flush brake fluid every few years
Lower transmission torque mount. See here
These Volvos often have spark plug coil failures over 100k miles. When one fails, the engine will lose some power and have a miss. I've also seen the message window report transmission shifting problems as well.
A good kit to have in the car is everything to diagnose and replace one of these coils. Here is a list of what you will need
Wifi OBD2 reader (Bluetooth ones often only work with Android)
An OBD2 App that works with the Wifi readers. Frees ones are available in App Store or Google Play
Small socket set. Torx bits. Long extensions. Everything necessary to pull the charged air pipe over the top of the engine on turbo cars.
Torx bits to pull the plastic head covers off. 10mm to remove the coil bolts
Extra coil. Used ones on ebay are like $15. Bosch equivalent is cheaper than Volvo. Avoid all other aftermarket.
So the ODB2 reader will tell you which cylinder is misfiring and you just replace that coil and be ready to go. Good kit to have in case you are far away from home garage.
Here is a video on removing the coils+plugs. I believe the torque bar removal maybe unnecessary, you should conduct a dry run to be sure.
Probably the most important thing to say about oil change for this car is use synthetic, synthetic, and synthetic. Did I say synthetic? :) You want to use 5w-30 in most climates for this car. I do 5000 mile oil change interval. Probably can go 7500 miles easily without any issues. You might ask, why should I pay for such expensive oil?
Synthetic oil basically cleans the engine much better than regular oil. So you want that. This car is also turbo charged, the turbine inside spins are much much higher RPM than the engine. You want to keep it lubricated well. The PCV system in this car is also rather complex and include very narrow passages. Running synthetic to keep it all clean is a good idea.
As for oil change directions, here is a couple of good source with pictures and a video
http://cvolvo.com/Central/Repair/B5254T.html
http://www.youtube.com/watch?feature=player_embedded&v=RYHcAZFI3Sw
For oil filter wrench, I have a solid Aluminum one made by Assenmacher. Google "V 410 oil filter wrench", online price is about $15 and another $10 for shipping (unless you order some other parts and get free shipping). Here is the link to this top of the line wrench.
http://www.asttool.com/detail_page.php?tool_number=V%20410
I drive my car onto ramps and do the oil change. This way, you can get a good look at any leaks while you are down there. Here are a few good things to inspect
Some people seems to have fried their ECC while removing it. It seems the "wait 5 min after shutdown" is probably a important step to allow the ECC to shut off completely after the engine is shutdown. What I do is turn everything off on the ECC, shut down the car, and wait 10 minutes before disconnecting the battery. And when reconnecting the battery, the key should be in position II. Read these portions carefully to avoid frying your ECC.
There is a way to get to the back of the ECC without disconnecting the power supply (to replace light bulbs). But I'm not sure if you can get to the fan spindle to clean it without removing some of the wires. See the following link for reference.
http://www.volvoxc.com/forums/showpost.php?p=80065&postcount=5
Here is a discussion thread on this
http://www.vvspy.com/w-agora4/view.php?bn=volvospy_newv70c70&key=1138456228&first=&last=&hb=-2
when changing the spark plugs, you may find wire looms protecting the wires to the coils easily crumbled and flaked apart. Here are a couple of notes
First, the loose plastic crumbs can easily drop into your cylinder. So change plugs on one coil at a time and do a good job vacuuming up the lose debries while working on each plug.
As a preventive maintenance, I removed the old looms, vacuumed up the flaked plastic debries and replaced them with new looms and wrapped them in electrical tapes. There are really high temperature plastic looms and are expensive and difficult to get hold of. I found the typical low cost 3/8 inch plastic looms did the job and are fine after over 30k miles.
There is a braided metal wire (ground wire?) that wraps around the filler pipe. This wire can saw a hole into the pipe. I simply loosened the nut at the connection, unwrapped it around the neck and reattach it for preventive maintenance.
http://www.brickboard.com/AWD/index.htm?id=957733
I also have a late build date 2001 XC70 (5/01 build date), this car doesn't have the braided metal wire wrapping around the filler pipe. Maybe a problem only for the early 2001 or none XC builds.
The front CV joint is next to the hot catalytic converter and the heat appears to dry out the grease overtime which causes the CV joint to wear and produce pinging sounds as the drive shaft experience sudden torque changes during gear shifts.
One person suggested since this CV is vented with a hole in the front metal plate and 2 slit/channels on the boot, one might just remove the boot clamp and use a syringe to squeeze in new grease. I've never heard of anyone doing this but its sounds like a great idea as preventive maintenance. Perhaps every 30k miles is a good interval.