Subaru 2.5 STi/Forester - GC or XD-3 good?

ringmaster · May 23, 2005

I have a brand new 2005 Forester XT (same 2.5L engine as the STi) and want to pin down a good oil for it. I did the first oil change at 500 miles from the stock fill to Pennzoil 5W30 dino and my plan is to leave that in until about 3000 miles when I will change over to full synthetic. Make sense?

The car will be driven hard, in a far more spirited manner than most Foresters will ever be...think STi driver

The owners manual suggests 5W30 for most situations but does mention 40wt. I have good access to the Esso XD-3 0W30 and 0W40 as well as GC. The XD-3 is about 1/2 the price of the GC so if it would be a good match for this engine I will use it. Maybe the 0W30 in the winter and the 0W40 for the winter....or is the Esso 40wt too heavy for this engine?

If neither of these three are good for my engine I will step up and spend the $$$ for some Motul 8100.

Thanks for your feedback

y_p_w · May 23, 2005

Not to shoot down your dreams of imagining you're a Formula 1 driver, but the engine is not the same as an STi, and the handling is nowhere in the class of an STi. It shares the same block though, but most of the parts are very different. Max boost of the Forester XT is 11.6 PSI. while the STi is 14.5. The Forester XT redlines at 6500 RPM while the STi tops out at 7500. It's still plenty powerful for a family vehicle though.

Mobil 1 5W-30 seems to do quite well in turbo'ed Subarus year round.

Paul_l · May 23, 2005

Actually, the long blocks are exactly the same. The difference in boost and power comes from a smaller turbo, smaller intercooler and difference ECU mapping. I own a 2005 Legacy GT which again shares the same long block, but with a turbo sized between the FXT and STi turbo, and surprise, it falls between the two in power output.

As to the handling, of course the FXT doesn't handle like an STi. Then again is rides much better and haul a heck of alot more stuff.

I've got GC in my Legacy right now and it seems to like it just fine. Should have a UOA in another 4K miles.

y_p_w · May 23, 2005

quote:

Originally posted by Paul_l:
Actually, the long blocks are exactly the same. The difference in boost and power comes from a smaller turbo, smaller intercooler and difference ECU mapping. I own a 2005 Legacy GT which again shares the same long block, but with a turbo sized between the FXT and STi turbo, and surprise, it falls between the two in power output.

As to the handling, of course the FXT doesn't handle like an STi. Then again is rides much better and haul a heck of alot more stuff.

I've got GC in my Legacy right now and it seems to like it just fine. Should have a UOA in another 4K miles.

I thought the STi had the cream of the crop with stuff like the water-sprayed intercooler plus stronger and/or lighter pistons, connecting rods, etc to withstand the additional boost. I was looking at one particular set of specs, and the STi uses different plugs than the Forester XT.

There was also one ungodly 0 to 60 time for the Forester XT of 5.3 sec, but I think most magazine tests have gotten it somewhere in the 6+ sec range.

AndyH · May 23, 2005

ringmaster: I think the Esso XD-3 0W30 or 0W40 or GC would all be fine choices. I will be switching over to GC in my STi when I hit 10,000 miles.

Up until then, I've been running conventional oil (Mobil Drive Clean 5w-30: sheared out of grade) and semi-synthetic (Motorcraft Semi-Syn 5w-30: sheared out of grade; Mobil 7500: still in the car, UOA to come).

UOA's for the Drive Clean and Motorcraft:
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=002305
http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=002541

[ May 24, 2005, 10:33 AM: Message edited by: AndyH ]

ringmaster · May 23, 2005

quote:

Originally posted by AndyH:
ringmaster: I think the Esso XD-3 0W30 or 0W40 or GC would all be fine choices. I will be switching over to GC in my STi when I hit 10,000 miles.

Thanks for the feedback. Do you think there will be any difference in engine wear or performance with the 30wt vs 40wt? I will do UOAs when the time comes but why not start off with the best oil possible

Do you think 10k miles is the magic time to change to synthetic? I wanted to change over before that.

AndyH · May 23, 2005

quote:

Originally posted by ringmaster:
Thanks for the feedback. Do you think there will be any difference in engine wear or performance with the 30wt vs 40wt? I will do UOAs when the time comes but why not start off with the best oil possible

I'd probably give both a try and have UOA's done. But I'd be inclined to start with the 30wt, as that's what Subaru specs in the manual as their preferred weight.

quote:

Originally posted by ringmaster:
Do you think 10k miles is the magic time to change to synthetic? I wanted to change over before that.

Tons of debate about this on various Subie discussion forums. After reading all of it, I decided to delay the switch to synthetic a bit. On the other hand, there are plenty of guys who made the switch at say 3,000 miles and don't have any issues with consumption, so I really don't know what the best course of action is.

ringmaster · May 23, 2005

[/QUOTE]I'd probably give both a try and have UOA's done. But I'd be inclined to start with the 30wt, as that's what Subaru specs in the manual as their preferred weight.

The XD-3 0W30 is 12.1 cSt at 100c which I understand is quite thick for a 30wt oil, so it is probably close to some companies 40wt, although I can't find the HTHS # for these.

I am just a little skeptical about using what appears to be a diesel truck/tractor oil in my car, but it is probably more marketing hype than anything?

SilverGGA@Work · May 24, 2005

Don't be afraid of 40 weight oils if your car does not see freezing temperature. The manual actaully lists 10w-30 and 10w-40 in the oil chart if your car sees 100F, and even thicker if you have it under severe low and temperature (towing). You need to pick your oil viscosity based on ambient temperatures and how you use the car.

I tried the T&SUV 5w-40 and had a good UOA. Now I am on Mobil 0w-40 because it is more of a gasoline engine oil, have the A3 spec, with Porsche approvals (boxer turbo), and sold everywhere else in the world as a highly regarded full synthetic. I will see how this one goes. I would have tried the GC but all I am able to find is the new "unknown" gold GC.

bluesubie · May 24, 2005

quote:

Originally posted by y_p_w:

quote:

Originally posted by Paul_l:
Actually, the long blocks are exactly the same. The difference in boost and power comes from a smaller turbo, smaller intercooler and difference ECU mapping. I own a 2005 Legacy GT which again shares the same long block, but with a turbo sized between the FXT and STi turbo, and surprise, it falls between the two in power output.

As to the handling, of course the FXT doesn't handle like an STi. Then again is rides much better and haul a heck of alot more stuff.

I've got GC in my Legacy right now and it seems to like it just fine. Should have a UOA in another 4K miles.

Click to expand...

I thought the STi had the cream of the crop with stuff like the water-sprayed intercooler plus stronger and/or lighter pistons, connecting rods, etc to withstand the additional boost. I was looking at one particular set of specs, and the STi uses different plugs than the Forester XT.

There was also one ungodly 0 to 60 time for the Forester XT of 5.3 sec, but I think most magazine tests have gotten it somewhere in the 6+ sec range.

Engine internals are the same. The only other difference than what Paul already mentioned is a different intake manifold.
Actual power is ~240 and ~260 lb ft. of torque according to two different dynos (Cobb and Vishnu)

The funny thing is that there is no difference in the oil recommendations in all current Subaru's. The 300 h.p. STi lists the same "preferred" 5W30 that my 1997 137 hp Impreza Outback Sport did. Gotta love CAFE!

My FXT UOA's:
GC
GC and M1 5W30 .

Link to the C&D article where they got a 5.3 0-60:
http://www.caranddriver.com/article.asp?section_id=3&article_id=6854&page_number=1

-Dennis

[ May 24, 2005, 02:37 PM: Message edited by: bluesubie ]

y_p_w · May 24, 2005

quote:

Originally posted by bluesubie:

quote:

Originally posted by y_p_w:
I thought the STi had the cream of the crop with stuff like the water-sprayed intercooler plus stronger and/or lighter pistons, connecting rods, etc to withstand the additional boost. I was looking at one particular set of specs, and the STi uses different plugs than the Forester XT.

There was also one ungodly 0 to 60 time for the Forester XT of 5.3 sec, but I think most magazine tests have gotten it somewhere in the 6+ sec range.

Click to expand...

Click to expand...

Engine internals are the same. The only other difference than what Paul already mentioned is a different intake manifold.
Actual power is ~240 and ~260 lb ft. of torque according to two different dynos (Cobb and Vishnu)

The funny thing is that there is no difference in the oil recommendations in all current Subaru's. The 300 h.p. STi lists the same "preferred" 5W30 that my 1997 137 hp Impreza Outback Sport did. Gotta love CAFE!

My FXT UOA's:
GC
GC and M1 5W30 .

Link to the C&D article where they got a 5.3 0-60:
http://www.caranddriver.com/article.asp?section_id=3&article_id=6854&page_number=1

-Dennis [/QB]

I read some specs for the STi, and it made it sound like there are strengthened connecting rods and pistons. Still - the major factor in favor of the STi would be the increased boost, larger intercooler, and electronics.

As for the recommendations for 5W-30 for all Subarus, I think an oil cooler in all turbo models can help quite a bit.

ringmaster · May 24, 2005

quote:

The funny thing is that there is no difference in the oil recommendations in all current Subaru's. The 300 h.p. STi lists the same "preferred" 5W30 that my 1997 137 hp Impreza Outback Sport did. Gotta love CAFE!

My FXT UOA's:
GC
GC and M1 5W30 .

Link to the C&D article where they got a 5.3 0-60:
http://www.caranddriver.com/article.asp?section_id=3&article_id=6854&page_number=1

-Dennis [/QB]

Dennis,

Thanks for the info and nice to see another FXT owner on here

It is funny that the same oil is suggested for all the Subie engine since the FXT and STi engine will obviously heat the oil more than the stadard 2.5L! Without a good oil cooler I bet I could see 140C oil temps under extreme use!

Your UOA with the GC looks very good, although I am not an expert at reading these. I hate to sound cheap, and really I am not, but the GC is about twice the cost of the Esso XD-3...is it worth it? I think the cSt and HTHS specs are fairly similar between the two

y_p_w · May 24, 2005

quote:

Originally posted by ringmaster:
It is funny that the same oil is suggested for all the Subie engine since the FXT and STi engine will obviously heat the oil more than the stadard 2.5L! Without a good oil cooler I bet I could see 140C oil temps under extreme use!

I wouldn't think so with the standard oil cooler (oil to coolant heat exchanger) which regulates the oil temps close to the thermostat temp. The filter mounts directly onto the cooler, and you should see an inlet/outlet for the coolant. I'd think that with the oil cooler, your oil temps might be lower than a NA 2.5 (w/o oil cooler) on a hot day.

Have you thought of swapping out the OEM tires for something with more grip and a higher speed rating? Outside of the STi tires, Subaru uses crappy tires from the factory.

rcy · May 24, 2005

quote:

Originally posted by SilverGGA@Work:
Don't be afraid of 40 weight oils if your car does not see freezing temperature. The manual actaully lists 10w-30 and 10w-40 in the oil chart if your car sees 100F, and even thicker if you have it under severe low and temperature (towing). You need to pick your oil viscosity based on ambient temperatures and how you use the car.

I tried the T&SUV 5w-40 and had a good UOA. Now I am on Mobil 0w-40 because it is more of a gasoline engine oil, have the A3 spec, with Porsche approvals (boxer turbo), and sold everywhere else in the world as a highly regarded full synthetic. I will see how this one goes. I would have tried the GC but all I am able to find is the new "unknown" gold GC.

Unless I've been reading oil weights wrong all along, isn't it the first number that should matter regarding freezing temperatures. The second number is the weight of the oil at operating temperature.

y_p_w · May 24, 2005

quote:

Originally posted by rcy:
Unless I've been reading oil weights wrong all along, isn't it the first number that should matter regarding freezing temperatures. The second number is the weight of the oil at operating temperature.

The first number is a spec for maximum viscosity at sub-freezing temps, which are different for each grade. The second number is for viscosity at operating temps (100°C).

http://www.finalube.com/reference_material/SAE_Viscosity_Grades_For_Engine_Oils.htm

What happens in between doesn't necessarily correlate directly with either number. Some 0W-30's are thicker than some 10W-30's at room temps (~25°C). A typical 0W-40 is going to be thicker than a typical 10W-30 at 40°C. However - at summer temps, almost any oil will be relatively thin.

AndyH · May 24, 2005

quote:

Originally posted by y_p_w:
Still - the major factor in favor of the STi would be the increased boost, larger intercooler, and electronics.

I'd also throw in the Brembo brakes, 6-speed transmission, and DCCD (driver-controlled center differential).

olympic · May 24, 2005

GC and XD3 are excellent choices and would work fine in your car. Personally I would start with the 0w30 XD3 since it's nearly a 40wt as is.

There is one big word of caution here though, neither oil carries the proper API ratings for your car, so if you blow the engine or turbo, Subaru could use that against you to deny warranty. Auto manufacturers are getting pretty sticky about these things lately so it's definitely something to keep in mind.

y_p_w · May 24, 2005

quote:

Originally posted by olympic:
GC and XD3 are excellent choices and would work fine in your car. Personally I would start with the 0w30 XD3 since it's nearly a 40wt as is.

There is one big word of caution here though, neither oil carries the proper API ratings for your car, so if you blow the engine or turbo, Subaru could use that against you to deny warranty. Auto manufacturers are getting pretty sticky about these things lately so it's definitely something to keep in mind.

I believe most non-European manufacturers selling in the US recommend an ILSAC "Starburst" oil, but "mandate" that the oil at least meet certain viscosity grades and API service standards. 0W-30/0W-40 are not in Subaru's owner's manuals in the US/Canada and theoretically could present an obstacle in regards to warranty claims. Legally they can't deny an engine warranty claim just because you used 0W-30, but some might tell you that you're out of luck because you didn't follow the manual.

The Europeans mostly don't care about API although they have their own ACEA standards. Each manufacturer now has its own specs and approval lists.

rjundi · May 24, 2005

Subaru's are very easy on oil even in the turbo versions as evidenced by the UOA's posted on this website. I think your plan is solid.

They do fine even with conventional oil as Subaru recommends. I need to post my UOA with 5k and Exxon-Super Flo in a WRX.

bluesubie · May 24, 2005

The oil coolers and the water cooled turbo's definitely help! Yeah yeah, DCCD, 6 speed and Brembo's. Showoff!

Only if we had the Forester STi here!

As to not following the manual, I'm on the fence on that one. The manual specifies "recommended viscosities" but not "required viscosities". Don't remember what it says about starburst oils. IMO, if it comes down to engine failure, your relationship with a dealer might be helful. I go to mine for services that I don't perform myself (spark plugs, brakes, etc.).

I'm running Michelin Pilot Sport A/S's on 17" Euro Forester OEM wheels. A big improvement over the stock "light truck" tires.

-Dennis

Subaru 2.5 STi/Forester - GC or XD-3 good?

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