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Interesting info on synthetic oil recommendation

52 messages,  Last post on Nov 21, 2010 at 6:00 PM

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Messages Page 4 of 6

#23 of 52 Re: Subaru oil change intervals [aatherton] by saedave

Sep 10, 2010 (10:59 am)

Replying to: aatherton (Sep 10, 2010 10:48 am)
The sand-cast semi-closed decks do not place stress on the head gaskets, which is why this design is being used for the new NA engines.
 
But where has Subaru revealed "semi-closed deck" for the 2011 NA Forester engine? We all would be pleased with that design and it was one of several reasons I bought a 2010 XT for my mainly slow city driving...as well as the better match of lower speed engine torque to the 4-speed auto trans.
 
Will the potential increase in manufacturing cost necessarily raise prices of all 4 cylinder models? If warranty costs have been high enough with the die cast blocks, an increase may not be necessary to maintain profit margins.

#24 of 52 Re: Subaru oil change intervals [saedave] by aatherton

Sep 11, 2010 (11:04 am)

Replying to: saedave (Sep 10, 2010 10:59 am)
"... where has Subaru revealed "semi-closed deck" for the 2011 NA Forester engine?"
 
They have not. You must infer it. This says the turbo and the diesel use the DOHC semi-closed deck which saves the head gaskets:
 
"The BOXER DIESEL adopts a semi-closed cylinder block deck to improve the rigidity around the head gaskets, following the precedent of the semi-closed type used in the Subaru EJ20 turbocharged gasoline engine."
http://www.boxerdiesel.com/engineering/en/03.html
 
Then these say the 2011 NA engine is also DOHC:
 
"... for the 2011 Forester... Also of note is the switch from SOHC to DOHC..."
http://www.autoguide.com/auto-news/2010/07/2011-subaru-forester-gets-new-base-en- - - gine-improved-fuel-economy.html
 
"... for 2011, the Subaru Forester gets a new volume engine... double overhead cams (vs. a single cam previously)..."
http://www.autoguide.com/auto-news/2010/07/2011-subaru-forester-gets-new-base-en- - - gine-improved-fuel-economy.html
 
You have to assume that Subaru, in making the DOHC engine standard across the line, will use the same semi-closed deck for all of them. In a month, you can go see the new engine on the dealer lots.
 
The new engine has two significant improvements:
1. For all models, replaces the breakable timing belt that had to be changed every 100K, with a permanent timing chain.
2. For the NA models, it replaces the open deck SOHC engine with the semi-closed deck DOHC engine that has unlimited head gasket life.

#25 of 52 Re: Subaru oil change intervals [aatherton] by saedave

Sep 11, 2010 (12:35 pm)

Replying to: aatherton (Sep 11, 2010 11:04 am)
You have to assume that Subaru, in making the DOHC engine standard across the line, will use the same semi-closed deck for all of them
 
You are using THE instead of A DOHC engine. I believe the XT engine was described as unchanged for 2011.
 
I hope you are correct that the semi-closed deck block is used in the NA engine.

#26 of 52 Re: Subaru oil change intervals [saedave] by aatherton

Sep 11, 2010 (1:33 pm)

Replying to: saedave (Sep 11, 2010 12:35 pm)
I meant that Subaru is using the same block design for all the engines -- the turbo,the diesel and now the naturally aspirated. For the turbo and diesel, this would not be a change. Only for the NA. Or, are you saying the DOHC turbo engine will stay with the belt drive while the DOHC NA engine gets the chain drive?
 
On the decks, I suppose you could read the sources posted and come to the opposite conclusion - that for 2011 Subaru has designed a new open deck block for the DOHC motor, for use in the NA models only. In spite of what they said that they know about the effect of open decks on head gaskets.

#27 of 52 Re: Subaru oil change intervals [aatherton] by saedave

Sep 12, 2010 (6:50 am)

Replying to: aatherton (Sep 11, 2010 1:33 pm)
Or, are you saying the DOHC turbo engine will stay with the belt drive while the DOHC NA engine gets the chain drive
 
That is the implication of the "unchanged" description. It would also mean no recertification cost for the XT right now, possibly a consideration. It also suggests to me that a next iteration of the XT engine might have the turbo below like the diesel. The mention of 2.0 liter to 2.5 liter displacements may also be a clue. I wonder what output a 2 liter turbo GASOLINE version of the diesel would have. I presume it would be tuned more for economy than the Japanese market turbos.

#28 of 52 Re: Subaru oil change intervals [saedave] by aatherton

Sep 12, 2010 (4:58 pm)

Replying to: saedave (Sep 12, 2010 6:50 am)
...that is the implication of the "unchanged" description. It would also mean no recertification cost for the XT..."
 
Some things are unchanged.
 
For the turbo, the engine has no changes requiring recertification. A change from belt to chain drive would not require recertification.
 
For the NA, the 2.5L has no changes to displacement or power.
But the NA does get DOHC and chain drive, for which it is called a new engine.

#29 of 52 Re: Subaru oil change intervals [aatherton] by saedave

Sep 13, 2010 (12:50 pm)

Replying to: aatherton (Sep 12, 2010 4:58 pm)
For the NA, the 2.5L has no changes to displacement or power
 
Not what I read:
1) more displacement
2) max torque at lower rpm

#30 of 52 Re: Subaru oil change intervals [saedave] by aatherton

Sep 15, 2010 (5:35 am)

Replying to: saedave (Sep 13, 2010 12:50 pm)
"For the NA, the 2.5L has no changes to displacement or power.
But the NA does get DOHC and chain drive, for which it is called a new engine."
 
"... Not what I read:
1) more displacement
2) max torque at lower rpm"
 
We are both reading the same article that says:
"... slightly larger displacement (2,498cc vs. 2,457cc)... horsepower remains at 170... Torque edges up from 170 at 4,400 rpm to 174 at 4,100 rpm..."
http://blogs.insideline.com/straightline/2010/07/2011-subaru-forester-gets-a-new- -base-engine.html
 
But I did not consider that increases of 41 cc and 4 ft-lbs were significant enough to mention as design changes that would call it a new engine.
 
The NA engine is called new not because of those insignificant changes in displacement and torque, but because of the DOHC heads and the chain-driven cams.

#31 of 52 Re: Subaru oil change intervals [aatherton] by aatherton

Sep 16, 2010 (2:42 pm)

Replying to: aatherton (Sep 11, 2010 11:04 am)
"... In a month, you can go see the new engine on the dealer lots."
And here's a photo now;
http://response.jp/imgs/zoom/249397.jpg
Less expensive industry standard plastic intake runners. One serpentine belt for all the pumps and accessories. Cam chains buried deep in front cover. Cam ends with their hydraulic and electronic controls protruding out the front.

#32 of 52 Re: Subaru oil change intervals [aatherton] by xwesx

Sep 16, 2010 (4:34 pm)

Replying to: aatherton (Sep 16, 2010 2:42 pm)
Hmm, yeah - that looks a LOT different than the current SOHC or the DOHC of years past. Even the dipstick is far removed. I can't say I would miss the timing belt, though!

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