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Hello All,

I'm trying to decide what oil I should be using in the motor on my new-to-me Forester. I brought it to FineLine Imports in Santa Rosa to get dyno-tuned and they suggested using Motul 15W50. The car came with a bunch of Motul 8100 X-Cess 5W40, so I assume that is what the prior owners have been using.

This is a weekend car so: it will put on miles slowly, and will be driven mostly on highways and country roads. I'm not going to drive it all that hard but ... what's the point in having a fast car if you can't go fast in it so I'll occasionally have some fun with it if the coast is clear.

Any thoughts are appreciated, my gut says go with 15/50 since FLI seems to have a great reputation, but I figured I'd get the forums thoughts.

What the car came with is: http://www.motul.com/us/en-US/produ...00-x-cess-5w40?f[application]=139&f[range]=25

But it looks like FLI is suggesting I use: http://www.motul.com/us/en-US/produ...[application]=139&f[range]=25&f[viscosity]=32
Thanks!
 

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You don't remotely need a 50 wt. Too thick an oil will rob you of power.40 wt is more than thick enough. 30 wt should be fine.
German Castrol 0W-30 is a thick 30 wt. If you want to hedge your bets go with a 50/50 mixture of the Motul 5W-30 and 5W-40.
 

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Do you have bearing clearances that specifically call for a 50 grade oil? Open class rally cars use Motul 300V 15W-50.

If your bearing clearances don't absolutely need a 50 grade, I would stick to X-cess 5W-40. We didn't build your engine so maybe they know better. If you do need a 50 grade, Mobil1 15W-50 is also an excellent oil. The Motul 6100 range is "Technosynthese" meaning synthetic technology (like Valvoline or N. American Castrol).

-Dennis


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Discussion Starter · #4 ·
You don't remotely need a 50 wt. Too thick an oil will rob you of power.40 wt is more than thick enough. 30 wt should be fine.
German Castrol 0W-30 is a thick 30 wt. If you want to hedge your bets go with a 50/50 mixture of the Motul 5W-30 and 5W-40.
Do you have bearing clearances that specifically call for a 50 grade oil? Open class rally cars use Motul 300V 15W-50.

If your bearing clearances don't absolutely need a 50 grade, I would stick to X-cess 5W-40. We didn't build your engine so maybe they know better. If you do need a 50 grade, Mobil1 15W-50 is also an excellent oil. The Motul 6100 range is "Technosynthese" meaning synthetic technology (like Valvoline or N. American Castrol).

-Dennis


Sent from AutoGuide.com App
Thanks everyone, yeah based upon what I had been reading I was wondering if I really need anything as thick as 15/50. The car has pretty ludicrous amounts of power (at least, to my mind) so I don't mind running a thicker oil if it'll support greater longevity and not-too-much of a performance hit.

The engine was built by COBB in Plano TX, so maybe I should call them and ask their opinion.
 

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Thanks everyone, yeah based upon what I had been reading I was wondering if I really need anything as thick as 15/50. The car has pretty ludicrous amounts of power (at least, to my mind) so I don't mind running a thicker oil if it'll support greater longevity and not-too-much of a performance hit.



The engine was built by COBB in Plano TX, so maybe I should call them and ask their opinion.

Let us know what they say.

-Dennis


Sent from AutoGuide.com App
 

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If I may add a guess....IF you were racing this engine in really hot conditions, a 50W might be called for. The way you will be using it, a good 30W might be perfect.
 

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Discussion Starter · #9 ·
Heard back from Cobb in Plano — they thought 15w50 would be a bit much too, and recommended sticking with Motul 5w40 Motul 8100 X-Cess. Great news since I have a bunch of it in the house!
 
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