H-4 Subaru

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Oct 2, 2010
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Anyone consider the H4 opposed four 2.5 Subaru engine as rougher on oil than any other? Mine's a 2004 SOHC in an Outback wagon original spec 5W30 or 10W30 or 10W40 SL even all the way to 0 degrees F, believe it or not. It has 121K, new head gaskets, no leaks, with a very slight slap when cold that goes away quickly after a mile or two. It's been suggested these shear the conventional energy-conserving oils and may warrant HDEO. Sounds nutty to me, but it IS a different configuration. I like it ok, it works great, it kinda bounces around doing it's own thing under the hood, all the power of this engine is in low-RPM ranges but it does have an unrefined and rougher feel to it than the transverse DOHC four-cylinders in the Hyundais I used to drive. There are lots of them around, anyone ever do a UOA on one of these? Lord knows there are plenty of HDEO in 5W30 or 10W30 I could run in it, but I'd prefer, obviously to go PCMO 5W/30 Syn for 7500 OCIs. Thanks!
 
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Dec 7, 2003
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The Subaru engine is quite smooth considering it doesn't need an extra shaft with weights to counter-balance the bad vibration of an I4
 
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I've used whatever brand name conventional 5W-30 is on sale in our 2006 Outback since we purchased it with about 38,000 miles on it. It now has 143,000 miles, and I've always changed the oil twice a year regardless of mileage. Some of those intervals are 7,000+ miles. It still runs like a top and doesn't use enough oil between changes to notice it on the dipstick.
 
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I'd recommend HDEO in the turbo models, but any 5w-30 should be fine in yours. I'd probably be using Maxlife.
 
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May 1, 2012
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From everything I've read, including UOA's, these engines prefer a thicker oil. The engines are smooth, but to me, they sound like a tractor engine and feel like a tractor engine. I like them. This is my first year owning a Subaru, but I've decided to run M1 5w40 TDT during the summer and GC in the winter. Also, these engines are fairly rough on their oil, so it's recommended by many on here to run 5k mile OCI's. This is what I'm doing. With the GC currently in her now, and a Napa Platinum filter, I also have a can of LM MoS2 in the crankcase. This summer, I'll keep using the same filter and just refill her with M1 TDT. So, every fall, she will get a fresh slug of GC, a can of LM MoS2, and a fresh Napa Platinum filter. In the spring, the filter stays, no more moly additive until fall, she just gets fresh TDT. Repeat until I hit 500k miles. LOL!! This is my strategy.
 
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Jun 6, 2006
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Great White North.. eh
Rough on oil? The ej25 has the best UOA's on almost any oil. What are you guys smoking? I used a thicker oil when it was on towing duty in the summer. Now it's a 30 weight year round.
 
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Originally Posted By: Phishin
... Also, these engines are fairly rough on their oil, so it's recommended by many on here to run 5k mile OCI's. This is what I'm doing. ....
NO NO and NO!.. These engines (EJ253) are VERY easy on oil. NO wet timing system, rollerized cam followers, no hydraulic lash takeup, high volume oil pump, moderate sump size, aggressive PCV plumbing. Just the stroke is very, VERY short(pistons like a z28 302 chevy)and they like a near A3/B4 ACEA lube not silly ILSAC water. For past cars, We used to mix XoM MC5k 5w30 and 10w40 Formula Shell 5w30 with Rotella Triple 10w30 to get good results. I've owned, IIRC 8 subarus - my wife has a new one now smile From Justy I3 banger to SVX boxer 6-pot.
 
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If your engine is rough you need a lash adj or refreshened sparkers (they like Denso TT NOT NGK due to the waste spark ignition on the SOHC.) If it doesn't run like a nice Porsche its out of tune.
 
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Mar 4, 2013
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As stated the EJ25 is pretty easy on oil. To prolong the life of the cam seals and valve cover gaskets, a HM 5w-30 isn't a bad idea. Use the Subaru coolant and additive in the non-turbos, and you car will rust out before your engine goes. What kills Subarus is the compounding cost of driveline repairs as they age. CV's, main rear driveshaft, wheel bearings, tie rods, Ball joints, steering rack, etc all wear out. At a certain point, they just seem to come at you one after the other. If you DIY, most of this stuff is pretty straight forward and cost is not bad. A center diff going out on a car with north of 200k is probably a death nail. Especially if it's due for tires (AWD is hard on tires) and has any rust issues.
 
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Nov 4, 2014
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Severna Park, MD
I take care of my step-son's 2006 Saab 9-2X Linear, which is a re-badged Subaru Impreza with the non-turbo SOHC EJ25 engine. He's a grad student and drives about 10k miles/year, coming up on 70k miles soon. About all I've done to it maintenance-wise is change the oil, air filter, and cabin air filter. I use Amsoil ASL 5W-30 oil and the Amsoil EA15K12 oil filter. This year I changed the power steering fluid, using Amsoil synthetic ATF. Also fixed the noisy rear brakes with new calipers, Wagner ThermoQuiet pads, and PowerStop rotors. This is the first Subaru I've ever touched and don't really know much about them. Anybody have any general advice about the engine or driveline?
 
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Originally Posted By: Joel_MD
Anybody have any general advice about the engine or driveline?
Sure. Keep an eye on the head gasket. A UOA couldn't hurt. It may need to be replaced at some point, but it isn't the end of the world. You're also due for replacement of the transmission and differential oils, and coolant. Use Subaru ATF, gear oil, and coolant with the addative. At 100k, do the timing belt, water pump, thermostat, idler pullies, tensioner, and associated gaskets.
 
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Auto or Manual? The question is what kind of coolant does it have? Standard green you can user the coolant tabs if you wish but you should not if it is blue(long life). Valoline makes a full synthetic Import ATF and Amsoil has one that meets ATF-HP spec. You don't need to use Subaru ATF, it is just easier. Same goes for gear oil.
 
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I'd like to add: if you have a manual transmission, I strongly recommend Subaru 75w-90, which has just recently been made available in quarts. I've tried several other varieties and found them all to perform poorly in the transmission.
 
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May 23, 2004
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Northeast
Looks like I'm in the minority on this one. I have a non-turbo 2009 legacy and from what I've seen on these forums, and in my own personal uoa's these engines are hard on oil in the sense that they tend to shear it down pretty quickly. It's true these engines are very low wearing engines, but like I said they do thin oil down pretty quickly. Here are 3 of my reports. It's worth noting that blackstone made an error on the second report, which contains 2 uoa's. It's interesting that the viscosity ranges are different on the two images. The cSt viscosity @ 100C range on one report is 9.1-11.3, and on the second report is 8.5-11.3. In the link below, the acceptable range for a 30 weight oil is 9.30 - 12.49, so I don't know what's going on there. http://www.bobistheoilguy.com/viscosity-charts/
 
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It's too late for me to edit that post again, so I wanted to clarify something. I thought blackstone made an error on the second report since they listed the 30w viscosity range as 8.5-11.3 cSt @100C, when the first report says 9.1-11.3 cSt @100C. Like I said above a number of other places online disagree with both of those ranges, and say 9.3-12.49 cSt @100C. Either way, it looks to me in all 3 uoa's the oil sheared down from a 30wt to a 20wt.
 
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Originally Posted By: Thermo1223
Auto or Manual? The question is what kind of coolant does it have? Standard green you can user the coolant tabs if you wish but you should not if it is blue(long life). Valoline makes a full synthetic Import ATF and Amsoil has one that meets ATF-HP spec. You don't need to use Subaru ATF, it is just easier. Same goes for gear oil.
My step-son's Saab 9-2X has the automatic transmission. I was thinking about changing the ATF, and I already bought the spin-on transmission filter. I have a tendency to use Amsoil products and trust the application guide on their website. However, it's strange that Amsoil has no recommended product for the Saab 9-2X auto transmission but if I look up the same year Subaru Impreza it recommends Amsoil ATF, which meets the specs for Subaru ATF-HP. I have no idea what coolant is in there. I should probably flush it and put something good in there. What coolant do y'all recommend?
 
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Originally Posted By: sxg6
Looks like I'm in the minority on this one. I have a non-turbo 2009 legacy and from what I've seen on these forums, and in my own personal uoa's these engines are hard on oil in the sense that they tend to shear it down pretty quickly. http://www.bobistheoilguy.com/viscosity-charts/
Exactly. These H-4's may be low wearing, but every UOA I've seen shows a high amount of shear. I've also seen some high spikes in lead, copper, and iron if the oil reaches too low into the 20 weights. This is why I'm running GC in the winter (thick 30 weight) and M1 TDT in the summer....and not going beyond 5-6k OCI's. I rest my case.
 
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Originally Posted By: Phishin
Originally Posted By: sxg6
Looks like I'm in the minority on this one. I have a non-turbo 2009 legacy and from what I've seen on these forums, and in my own personal uoa's these engines are hard on oil in the sense that they tend to shear it down pretty quickly. http://www.bobistheoilguy.com/viscosity-charts/
Exactly. These H-4's may be low wearing, but every UOA I've seen shows a high amount of shear. I've also seen some high spikes in lead, copper, and iron if the oil reaches too low into the 20 weights. This is why I'm running GC in the winter (thick 30 weight) and M1 TDT in the summer....and not going beyond 5-6k OCI's. I rest my case.
If yopu over fill instaed of under fill yoiull be foaming the oil. The cranks is super short stroke so relative piston speed is low but they are hot under dome ( due to 4" dia) and can have a good load on the bore lube at BDC and TDC turnaround. Again, really Nothing hard for oil about this engine - no wet timing system, no SUB, no pushrods, no lifters no HLA. It got Rollerised rockers. ILSAC oil is "weak" Run a REAL oil and you'll be good to go. Sorry the US doesn't allow many "real" oils to be readily available due to emissions preservation and CAFE smile
 
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