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2005 Forester
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8 Posts
Discussion Starter #1
I am buying a 2001 with 93k, I have read that after 50k on a car you should not switch to synthetic oil, because you will cause oil leak from the loosening of deposit around the seals and gaskets. Anyone have any experience on using synthetic oil on higher mile engines?

The timing belt and head gaskets were just replaced, if that matters.
 

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Premium Member
2008 2008 2.5i-2018 XT
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13,205 Posts
When I buy a new car, new to me car, I use Valvoline Full or Blend Synthetic from the first change on. No problems and those below freezing winter starts are always easy.

Valvoline Syn would never have been a problem as it is really a GroupIII oil...meaning a very highly refined dino oil that can be called "Full Synthetic".

The problem in the old days was that the "True Syns" like the old Mobil I were a Polyalphaolefin (PAO) which shrank seals bc it had no seal swelling compound..hence leaks. Esters (like Redline) had the opposite problem...they caused seals to swell and deteriorate. Todays "True Syns" Amsoil, Redline, German Castrol, Royal Purple, and Motul now have additives that do not cause seals to shrink or swell.
 

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2019 Outback 3.6R ..... 98 Forester S - Atl, GA
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I have switched a bunch of high mileage cars over to Syn. never had an issue ... its not that Syn. will cause a leak ...but it can leak more through an existing leak !!
Well said!
But I still run plain old dino and change it way too often.
 

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2009 Forester
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223 Posts
AMSOIL is a true Group IV Synthetic, and talking to your friendly Subaru Forester AMSOIL guy will get you better pricing than AMSOIL.com. Switching to synthetics very rarely causes leaks, and only on vehicles in poor condition with cracked or rotted gaskets and seals. I've switched over vehicles that were over 16 years old with 200k+ miles and no leaks.

-Chuck
Twin Port Sales

 

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2002 Forester S
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270 Posts
Bollox. My wife's 02 had 104k on the clock and I put in Valvoline Maxlife Synthetic. Works great and doesn't leak a drop.

Maxlife Syn is their Synpower with extra seal conditioners and detergents in the add pack.

Else, I'd run M1 HM.
 

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2009 Forester
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223 Posts
Comparison data on AMSOIL SSO 0W30 and other competing products.



AMSOIL Signature Series 0W-30 Synthetic Motor Oil (SSO)

Kinematic Viscosity @ 100°C, cSt (ASTM D445)
10.3

Kinematic Viscosity @ 40°C, cSt (ASTM D445)
56.6

Viscosity Index (ASTM D2270)
173

Cold Crank Simulator Apparent Viscosity @ -35°C, cP (ASTM D5293)
5927

Pour Point °C (°F) (ASTM D97)
-51 (-60)

Flash Point °C (°F) (ASTM D92)
230 (446)

Fire Point °C (°F) (ASTM D92)
246 (475)

Four-Ball Wear Test (ASTM D4172: 40kgf, 150°C, 1800 rpm, 1 hr) Scar diameter, mm
0.406

Noack Volatility (ASTM D5800) 250°C for 1 hour, % weight loss
8.7

High Temperature/High Shear Viscosity cP, X°C, X s-1 (ASTM D4683)
3.2

Total Base Number
13.2


Notice the Cold Pour Point. -60 degrees Fahrenheit. That means at temperatures as low as -60, this oil will still flow, meaning that your oil pump (and turbo if equipped) will get oil pressure immediately during cold weather startups.

-Chuck
 
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