Since i am here, i will lend you my expertise with both subaru and working at an oil change facility. I will compare what is recommended, and suggest my personal preference for brands/fluid types, which are suitable for all season and temperarure ranges for a northern temperate climate that sees from -20 degrees to 100 degrees F:
Front and rear differentials: Front 1.2 qts, rear .80 qts; 80w90 conventional or 75w90 synthetic, API GL-5 for helical or pinion gear. I use Mobil1 75w90 brand fluid, $10 per quart, 2 quarts services both diffs. Service schedule every 30,000 mi for everyday use, 15,000 mi for heavy use, off road, mud and water, etc
Automatic trans service from 30,000 to 60,000 mi, or 15,000 for extreme use such as towing or off road duty. If i am not mistaken, the 4eat fro 2009 uses dextronII/III spec fluid, conventional or synthetic. If in doubt, use a milti-vehicke ATF such as
Valvoline Max Life ATF, Cam 2 Multi-vehicle ATF. I am running the cam2 in my 98 legacy outback. Where i work, retail price is $119.99 for the Cam2 synthetic milti-ATF, or 89.99 for a conventional dextron II/III with an optional additive to bring the conventional ATF to chrysler atf+4 (mitsubishi), Mercon V or LV, (ford) or Dextron VI (GM). Dextron 6 is backwards compatible, so any modern-spec ATF will work in the subaru.
For th e coolant, service the factory fill after 5 years or 50,000 mi, Definitely at 100,000 mi along withthe timing belt and water pump. Maintaining the coolant system in the subaru is of utmost importance to avoid potential head gasket issues. It is best to use the Subaru brand coolant and the coolant conditioner. If using a generic fluid, use the green stuff, silicate free, and not the orange 'long life' coolant. A product like blue devil or k-seal can be substituted for the subaru coolant conditioner. For the green coolant, service every 24 months or 30,000 mi. The purpose for replacing the coolant is to replace the anti corrosive properties, as there are sacrificial elements dissolved into the fluid that wear away, much like a zinc rod in a hot water heater, if you understand galvanic corrosion or electrolysis, as dissimilar metals in a fluid(electrolite) will act as a cathode and an anode. I am running the straight green stuff. Since my engine (ej25d) is historically known for premature HG failure, i may consider the k-seal product as a preemptive measure. Usually pattern HG failures occur from between 125,000 and 150,000 mi. Mine has 133,000 on the odo.
For oil, change the oil from 3500 mi to 7500 mi, depending on conventional or synthetic oil. All oil must meet current standards such As global standard ISLAC GF-5 and American standard API SM, SN. A little known secret is that 'premium conventional' oil is technically a semi-syn and has a service life of up to 5,000 mi. My preference is a name brand oil such as Mobil 5000, Mobil Super High Mileage, or Mobil1. For oil weight and viscosity, the engine is installed with 5w30 from the factory. For summer temps above 50 deg F, a 10w30 oil is more appropriate. Same for prolonged highway or high RPM operation. "5w30 is not recommended for prolonged (sustained) high speed operation" according to subaru owners manual in regards to turbo since 1983. A 10w40 oil is appropriate for summer temps if the engine is consuming a quart between oil changes. 5w40 is also appropriate, as well as for winter. With a full synthetic oil, 0w40 is a wise choice as it flows best for cold starts and winter, but also is 40 wt for summer temps and high speed operation. For a conventional, 10w30 or 40, for synth blend, 5w40, for full syn, 5w40 0r 0w40. Examples of brands are Shell rotella t6 5w40, Mobil1 TDT 5w40, and Mobil1 European formula 0w40. I use the mobil1 ow40 and mobil high mile 1030 or 10w40. The proper weight is more important than which brand. If you do your searching , you will see a lot of argument for mobil vs rotella, but the argument really is about 5w30 vs 5 or 15w40. And for the record, Mobil1 is a group 4 synthetic ester, so if you read anything about mobil 1 not being a true synthetic or group 3 paraffin oil, they are mistaking for mobil super synthetic, which is a different line than mobil1 (my oil shop carries mobil)
With extended oil change, or any weight or brand of oil, in general, with any vehicle, it is wise to check the oil level as often as you fuel up. Subarus can and use oil. Causes for consumption can be from high mileage on the engine, failed or clogged PCV system, or too light of an oil grade. Ypu should expect to add a quart every 2-3,000 mi whether the engine is using oil or not. The 40 wt oil should do better with consumption. Consumption can vary depending on driving dynamic. For example, a 98 forester, can drive 2500 mi out of state and back, and not use a drop of oil, but the same car withthe same oil (5w30) can use a quart in 2 weeks of city driving. Just make a habit of checking the oil level often and you will be alraight regardless of oil weight or brand.
Keep the tires inflated to even pressure. Check and add air while tires are cold. Ths door sill may suggest some 28 lbs of pressure, but this is best for off road or snow footprint, but for street and highway driving, 35-40 lbs will lend to better fuel economy and tread wear. It is important that all 4 wheels be within 1/4 inch diameter of eachother to keep the AWD happy. Rotate the tires from 6-8000 mi, or every other oil change. Rotation should follow a FWD/AWD pattern rather than a 4WD/RWD pattern. Baxk tires move to front, front tires criss corss to the rear. After every other tire rotation, all 4 wheels will hve had the chance to wear from eaithe direction, from either side, to promote even tread wear. Without regular rotations, you will find the front tires wear much sooner than the rear, and the front tires will tend to wear the outer edges of the tires. Hence the need to rotate them often.
Air filter mileage can vary depending on driving environment. 15,000 mi for dusty conditions, 30,000 mi for ideal conditions. In the oil change industry, on average with average vehicles, i see filter replacements about 20-25,000 mi for mixed urban driving. If you are inspecting and replacing the filter yourself, you will want to see light shine thru the filter pleats. Once you can only see light at the edge of the pleats, it is time to replace it. It is ok to have a little bit of sand or dust bunnies between the pleats as long as light can shine thru.
Inspect the brakes at each tire rotation. To avoild complications with calipers, disassemble and clean the brakes and grease the slide pins once or twice a year. Ideally, once before winter, and once after winter, especially if your area uses road salts to melt ice. Here in wisconsin, if you just let the brakes go intil the pads are down to the metal, you can count on seized caliper slides before, or a stuck piston after replacing the pads.
Another thing to consider, although you haven't asked, is to prevent rust. Common rusty spots are the rear wheel arches where the bumper meets, as there are plastic tabs that secure the bumper, and rust will begin there. Same withthe bottom of the wheel arch where it meets the rocker sill. This is because dirt and debris will accumulate and trap moisture, promoting rust, especially when road salts are applied in winter. Keep this are a clean and be sure to wash it out with a sprayer or by hand with a rag when washing the car. You can pull out the rubber stone guard strip to clean and wax this area when you wash the car. Another rust place is the front fenders behind the mud flaps. Dirt and leaves will accumulate there from within the wheel arches, and from the wiper cowl. Durt will pack in and trap moisture causing rust from inside out, behind the paint. It wouldn't hurt to take out the bolt to gain access and clean behind there, and replace the bolts with stainless steel. When using a sprayer or hose, open the door and blast it behind the fender between the door hinges. By hand, you may be able to pull down the plastic fender liner and rinse it from behind.
Don't be afraid to get your hands dirty on the car. Although subarus are particular about maintenance, they are wonderfully easy to service. You should have no qualms about dong a routine service like replacing a starter or alternator with no mechanical background and basic hand tools. You have this forum, so $100 bucks in tools can save you more money for less than the cost of one hour of dealer labor rate.