Leaderboard

We entirely disregard Subaru's recommendations on oil unless the car is under factory warranty. We average about 1-2 oil changes 5 days a week for customers - usually schedule these at 9am to get them out of the way and out the door. THE ONLY TIME we use anything other than 5w40 (or 5w50 for 400+ HP), is on cars that are under warranty obligation to use 5w30 or 5w20. Everything else gets 5w40 Amsoil Euro FS. This is an XL oil with a 5w40 spec (normal XL is 10w40). https://www.amsoil.com/p/sae-5w-40-fs-synthetic-european-motor-oil-efm/ It's rated for 12,000 miles. We run it for 6,000 miles since the WIX filters rate about there and Subaru's shear their oil and dilute it with fuel (especially the turbo models) causing some level of consumption after about 2500 miles and we can't trust most customers to check their oil. I'm quite sure that all our customers combined have 10's of millions of miles on this oil and we have NEVER seen a failure related to oil breakdown, sludge, or really any lubrication related failure other than customers that burn all their oil up or leak it out and cause mechanical damage from the complete lack of oil. I have torn down engines due to failures unrelated to the oil - in one case we pulled down a built engine due to a cracked cylinder liner - plugged injector from tank contamination caused a lean condition under boost and the high cylinder pressure blew out the sleeve. Even under the SEVERE detonation conditions that resulted in a cracked cylinder sleeve we saw ZERO damage to the bearing journals running 5w40 Amsoil. So I'm not inclined to change my process. And I have reviewed the specs of the new engines vs. the older engines with respect to bearing sizes and clearances and oil pump specifications, etc - there is no difference between the older engines that specified 10w30 and the newer engines that specify 5w20. Subaru changes the spec based on meeting emissions and economy guidelines, and changes the recommendations for different markets. They have in the past offered 40 and 50 weight racing oils with their branding - in other markets. Viscosity is chosen based on engine LOAD. Higher load requires thicker oil so it doesn't squirt out of the bearings under high cylinder pressure. Take note that I own and manage a performance shop - as such my customers are largely composed of "Enthusiasts" who often drive their cars at the hard. I myself drive all my cars hard and have blown up my share of engines personally. Hard driving equals high load. And thus a step up in viscosity is warranted. GD

Ideally, careful oil pressure monitoring and lab testing of the used oil will tell you what works best for you. For my daily drivers, I'm wholeheartedly of the opinion that the best oil is new oil. I use the cheapest 5w30 I can get my hands on (usually Walmart or Fleet Farm house brands) and change it more often then recommended. I'm a bit more picky on filters, but not by a lot. I have a pressure gauge and a 11mm oil pump on my EJ25 daily, and don't see much of a difference in pressures summer to winter (it's 93*F here today, and not uncommon to see 40 below days in the winter. Although my car does spend overnights in an unheated/uninsulated garage, so we have to get a pretty good gold stretch for it to be below zero in the mornings.

The timing belt was old, high miles, and/or not a Subaru/AISIN brand belt. That's why it broke. It had nothing to do with the transmission.

Only manual transmission cars have the guide. And no - an auto isn't going to break a belt. Even a manual isn't going to break a good condition belt. Skip a few teeth maybe, but not break it in half. The belt was old and past it's service life or was off-brand and poor quality if it's broken. And heartless is correct - buy a Subaru (or any car with a timing belt and an interference engine) - you are immediately remiss in your duties if you don't change the belt, water pump, and all associated with QUALITY Japanese made components. You generally have no idea if/when it was done or what quality of parts/labor were used. And it sounds like the transmission/torque converter are garbage. GD

Sold

coupla things; 1. You could investigate Blackstone labs and test your used oil. 2. You might enjoy reading at www.bobistehoilguy.com

Use synthetic. The end. Lol. If cost is a concern extend your oil change intervals as synthetic allows. But check oil level often. Brand and weight don’t matter if you want top shelf get amsoil and read GDs data driven commentary on past threads. You have a 2007, those blow the short block all the time due to oil loss/low oil, 10,000 times before they do due to weight or brand. Use synthetic. The end. Most info is short sighted, anecdotal and/or impractical and useless. Practically speaking it doesn’t matter, except use full synthetic for your control rings. Follow the owners manual for weight of that year 5W and 10w are both fine. Varying weights isn’t necessary but not a terrible idea either. Most responsible car owners with average daily driver commuters change their oil well before the oil is problematic. so it’s not like they’re being pushed to the limits where one brand will perform better than another Subarus are making 200,000+ miles all day long on whatever oil is on sale. And there’s people promoting every brand as awesome because some oil wizard told them about it and they’ve never had issues. Well join the club buffoons, that’s everyone, no matter the brand. Lol. And that’s why no one can resist talking about it - theyre guaranteed to be right, or partially right....because most of what people talk about doesn’t matter empirically or practically. I’ve never blown an engine and have driven a ton of Subarus past 200,000. Is it because of my meticulous attention and robust knowledge of oil? Good grief, no. They fail due to oil loss, low oil and neglect. Use synthetic to keep those control rings clean. your year is prone to low oil. Your best protection is synthetic, frequently checking the oil level and not brand or weight, beyond obvious guidelines. Those engines are routinely found with blown short blocks due to oil starvation not weight and brand. There is a small range where better oils will protect in adverse conditions like low oil where the temps and over cycling degrade the oil properties. But the range where that happens before it hits low enough oil to destroy and engine no matter what oil is pretty narrow relatively speaking. But still amsoil would offer some additional protection there.

Paul, I ran 10W40 in my '83 EA81 after it hit about 100K, still runs to this day with about 400K. Mostly Quaker State back then. On my '96 EJ22 I ran mostly 10W30, but I got it with over 200K well maintained miles on it already, and AFAIK, it still runs good. Mostly Castrol, sometimes NAPA brand oil. On my present 2008 EJ25 with ~225K, I (and the previous owner) have been running Castrol 5W30, as recommended in the manual. I switched to "High Mileage" Castrol at about 210K. No engine issues.