Subaru Reliability
Subaru's are among the most reliable and durable vehicles available.
Here are some notes regarding me personal experiences with Subaru's, and knowledge that I have gained through exhaustive searches of the internet and discussions with other owners.
Engine
Generally very reliable. My 1985 GL's EA81 engine ran for more than 500,000 km before I swapped it with a lower mileage replacement (300,000km). The original EA81's oil pump was not producing enough oil pressure, causing the lifters to click. I purchased a whole scrap 1987 GL for $150, which allowed me to do the simple engine swap.
My 1993 Legacy's EJ22 engine ran for 366,000km before the car was totalled in an accident. During its life, all that was required was an oil pressure sender ($20), water temperature sensor ($20), camshaft rear oil seal ($4), front crankshaft oil seal ($10) and water pump ($85).
My current 2001 Outback's EJ25 engine has experienced no problems in the first 50,000km.
Some EJ25 engines experience head gasket failure. The outer part of the gasket which prevents coolant from leaking from the water jacket to the outside develops a small leak. This is usually noted in cold weather (below minus 15 Celcius), when some coolant drips onto the exhaust system. Once the engine is warm, the leak seals itself. Eventually this small problem will grow into a larger one. Subaru has not yet acknowledged that this is a real problem, but some websites claim that as many as 25% of the EJ25 engines are affected, however owners write in to express the frustration of having the problem, and owners how don't have any problem seldom report anything positive. The repair involves replacing the gasket, however the root problem appears to be a defect in the manufacture of the engine block. If you experience this problem, complain to both Subaru customer service and to the National Highway Transportation Safety Agency (NHTSA).
Link to this sites Recall and TSB section: EJ25 Head Gasket Leak
NHTSA report a defect page: http://www-odi.nhtsa.dot.gov/ivoq/
A website devoted to Subaru's denied warranty claims: http://www.deniedmywarranty.org
Automatic Transmission
Generally very reliable. Some earlier (1990-1994) models had some issues addressed by various TSB's. Most issues were related to the transmission cooler and filter.
Manual Transmission
Generally very reliable. Common complaints are seal leaks which are easily repaired. Uncommon complaints are noisy internal bearings. Some WRX owners are shattering gears, but I believe that this can be attributed to driver abuse.
My 1985 GL's dual range 5 speed manual transmission ran for better than 600,000 km before it was swapped (from my $150 donor car).
My 1993 Legacy's 5 speed manual transmission developed a noisy bearing at about 225,000km. I continued to drive it for another 141,000km before the car was destroyed. I was quoted $900 to repair, while a complete transmission from a scrap yard was under $400!!. I was going to replace the transmission when the clutch wore out, but the car was destroyed in an accident before that happened.
Many WRX owners are breaking gears in their manual transmissions, primarily first gear. This is not because the gears are weak, as the WRX gears are at least 50% stronger than those in other vehicles of similar size and weight. The issue is that with All Wheel Drive, it is very difficult to induce wheelspin unlike with front or rear wheel drive vehicles. If the engine is revved and the clutch pedal is released, all of the force is applied to the transmission gears, while in a two wheel drive vehicle you will get wheelspin which has the effect of reducing stress on the transmission.
It is imperative that you DO NOT rev the engine and drop the clutch in the WRX, or in any other Subaru. Rapid destruction of the transmission is the result of this behaviour.
Clutch
Generally quite durable. I got better than 400,000 km on my 1985 GL's clutch, and had 366,000km on my 1993 Legacy's original clutch when it was destroyed. Some owners are complaining about clutch wear out in as little as 60,000 km on their late model Legacy's and Outback's. I believe that driving habits are responsible for most of these premature wear outs. The Outback clutch should be good for 150,000km++++.
1999-2002 model year vehicles with the 2.5litre engine and 2002 model year 2.0 litre turbo WRX models may experience a cold clutch judder issue. Subaru will replace the clutch under warranty. See TSB 03-51-02 dated 01/15/03 which addresses this issue. Print the TSB and take it to the dealer. Some dealers will refuse to due the work under warranty, or to reimburse an owner if this work was performed at their expense. In these situations complain to Subaru directly.
Sometimes the replacement clutch experiences the identical problem. If so it may be due to the use of the incorrect replacement clutch or to the simple resurfacing of the flywheel. Verify that the replacement part numbers match the ones listed on the TSB, and insist on a new flywheel.
A website devoted to Subaru's denied warranty claims: http://www.deniedmywarranty.org
Drivetrain
Generally very reliable. My 1985 GL required a replacement rear drive shaft and a complete front axle (CV/DOJ assembly). My Legacy required a new front axle shaft at 310,000km, surprisingly I was able to obtain one at Canadian Tire for $110, which is very inexpensive for this part.
Front Constant Velocity (CV) joint and Double Offset Joint (DOJ) protective rubber boots fail every 3-5 years. Usually the DOJ boot fails do to exhaust heat. Inspect your front axle shafts every 2 weeks to detect this problem early. If the joint is unlubricated and exposed to dirt it will quickly fail leading to a far more expensive repair.
Brakes
Generally very reliable. On my 1985 GL, I had to replace both rear drum brake assemblies and one front calliper, but only after 450,000km of wear and tear!! On My Legacy, I had to replace a slide bolt on the right rear disk calliper, the original was sticking causing uneven brake pad wear. Brake pad life was about 75,000 km on my GL and better than 125,000 km on my Legacy. My 2001 Outback with 52,000 km on it has at least 60% brake pad life remaining. Some owners complain about warped rotors, but this is likely due to driving habits. I have a yet to warp a rotor on any of my Subaru's. My Legacy was totalled in an accident at 366,000 km with the original, never serviced brake rotors. One important thing with Subaru (and all other makes as well) is yearly brake maintenance. Each spring I recommend that you do the following:
By doing all of this once a year you will virtually guarantee that the brake assemblies (pads and rotors excluded) will last for the life of the car, it will also help to guarantee that the braking force is even.
Electrical System
Generally very reliable. In a combined 1 million KM neither my GL or Legacy experienced a failure of an electric window, lock or mirror. The alternators in both the GL and Legacy experienced a failed voltage regulator but only after 250,000km of usage.
The stock Subaru batteries last 5 years, and then fail in winter. But this is typical of OEM batteries.
Body
My 1985 GL had significant corrosion which led to its retirement. The chassis rusted through near the firewall where the front suspension is attached. However the car was driven for 12 years on heavily salted roads.
My 1993 Legacy was driven for 8 years on heavily salted roads. The body was treated with rust treated each spring, and as a result it had no rust whatsoever when it was destroyed in late 2000 with 366,000km.
The rear wheel well lip and the front fender kick area are the two the most common locations for rust to occur. With rust treatment neither of these areas will rust for at least 10 years in most areas and at least 6 or 7 years in heavily salted areas.
Body Hardware
After ten years my GL had two problems, the drivers door handle wore out, and the rear gate lifters failed. My 1993 Legacy had no problems.