Thicker Oil and Variable Valve Timing

J

JosephH1

Joined
Aug 2, 2007
Messages
119
Location
Lewiston, NY
Hi, I have an oil burning 2017 Subaru Forester (2.5i, 82k miles, non turbo, on it's second short block, STILL burning 1 qt every 1,000 miles). I have tried a thicker oil (0w-40) and cut oil consumption by 50%. My question is what impact a thicker than spec oil may have on the variable valve timing components? I do not want ease one problem and cause a 2nd problem. Should I be worried about a heavier oil and VVT? I am considering switching to a High Mileage oil at this point. TIA!
 
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You are going to get answers all over the map for this one. My personal experience is it is very engine dependent. People say with Fords for example that you have to use 5W20 in the Coyote engines, but mine specs 5W50 with no internal differences including the part numbers for the TI-VCT components.
 
Originally Posted by bdcardinal
You are going to get answers all over the map for this one. My personal experience is it is very engine dependent. People say with Fords for example that you have to use 5W20 in the Coyote engines, but mine specs 5W50 with no internal differences including the part numbers for the TI-VCT components.


My 2013 GT500 also specs 5-50 but Shelby America techs told me that was only because people track and race the cars....its a bored out mod motor. I run 0-40 M1 Euro in it and have run 5-30 in the past as I don't race her.
 
Originally Posted by JosephH1
Hi, I have an oil burning 2017 Subaru Forester (2.5i, 82k miles, non turbo, on it's second short block, STILL burning 1 qt every 1,000 miles). I have tried a thicker oil (0w-40) and cut oil consumption by 50%. My question is what impact a thicker than spec oil may have on the variable valve timing components? I do not want ease one problem and cause a 2nd problem. Should I be worried about a heavier oil and VVT? I am considering switching to a High Mileage oil at this point. TIA!



I may or may not have ran a 0w-40 through my 2018 with the same engine. Not because I'm having oil consumption, but because I got a bunch of it for $1 a quart. I did notice once the temperature started to cool off last fall, I started having some weird "chugging" at part throttle until the oil temp came up. As soon as I changed out to the recommended 0w-20 , it was fine again.

Of course, this is all hypothetical, because I always stick to the MFR recommendation while under warranty
wink.gif
Also, because mine is a manual transmission, there may be different tuning to make it meet emissions.
 
I'm sure there are engine models that care, and maybe a specific engine or two, but, motor viscosity changes quite a bit, from -40C up to 100C. [I realize oil gets hotter than that in the rings and such, but that oil gets a chance to cool before it gets to the valvetrain.] I suspect that your engine won't care--if anything, in some markets it may be listed as an acceptable oil in the owner's manual.
 
Subaru says that you can run a 5w30 or 5w40 conventional if 0w20 synthetic is not available but you're supposed to use a 0w20 the next oil change, to me that translates to the engine will operate just fine with thicker oil but due to the fuel economy and emissions information we submitted to the government we can't tell you that you're allowed to use them all the time. Plus euro 0w40 runs on the very thin side, usually just over the minimum viscosity necessary to qualify as a 40, so it's more like a thick 30.
 
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Tossing warranty aside, you can also look up the oil recommendations for your same engine in a different country, say Australia, and see what that shows.
 
Originally Posted by Miller88
Originally Posted by JosephH1
Hi, I have an oil burning 2017 Subaru Forester (2.5i, 82k miles, non turbo, on it's second short block, STILL burning 1 qt every 1,000 miles). A friend tried a thicker oil (0w-40) and cut oil consumption by 50%. My question is what impact a thicker than spec oil may have on the variable valve timing components? I do not want ease one problem and cause a 2nd problem. Should I be worried about a heavier oil and VVT? I am considering switching to a High Mileage oil at this point. TIA!



I may or may not have ran a 0w-40 through my 2018 with the same engine. Not because I'm having oil consumption, but because I got a bunch of it for $1 a quart. I did notice once the temperature started to cool off last fall, I started having some weird "chugging" at part throttle until the oil temp came up. As soon as I changed out to the recommended 0w-20 , it was fine again.

Of course, this is all hypothetical, because I always stick to the MFR recommendation while under warranty
wink.gif
Also, because mine is a manual transmission, there may be different tuning to make it meet emissions.


I have the manual transmission as well. Of course this is hypothetical, as we all follow MFR recommendations during the warranty. Of course, I am not planning to eventually run anything radical, likely a high mileage oil in xw-30 or xw-40, maximum. Or maybe a low SAPS to try and save the converter.
 
I, hypothetically, may be running a high mileage 5w-30 in it now. Trying different things now to eliminate the weird resonance/rattle that it has under light throttle at 2500RPM.
 
I don't have any logs to prove this on this laptop (RIP old lappy), but for my previous '08 STI I would see frequent AVCS fluctuations, even when the engine was only slightly warmed up. I used 5W-40 in that engine, which called for 5W-30. I believe that hydraulic oil is hydraulic oil and it doesn't take much to essentially slide an actuator for VVT operation.

As has been said, there may be some weirdo engine out there with super small orifices that cares about oil viscosity, but I just can't believe it.
 
It won't hurt a thing. The 0W20 is only spec'd to help them meet CAFE standards with no regard to engine longevity. That thin oil is why your on your second motor and now eating oil again.... put something else in it for gosh sakes!!! Subarus hate thin oil! I ran 40Wt in my 08 Legacy GT all the time and never once did I have any AVCS issues. The car was sold with 178k miles on the clock, original engine and barely used any oil.
 
Originally Posted by blufeb95
Subaru says that you can run a 5w30 or 5w40 conventional if 0w20 synthetic is not available but you're supposed to use a 0w20 the next oil change, to me that translates to the engine will operate just fine with thicker oil but due to the fuel economy and emissions information we submitted to the government we can't tell you that you're allowed to use them all the time. Plus euro 0w40 runs on the very thin side, usually just over the minimum viscosity necessary to qualify as a 40, so it's more like a thick 30.


A 40 is not a "thick 30" when it meets viscosity requirements of a 40 and not a 30. A 40 is a 40 and a 30 is a 30.
 
Originally Posted by wemay
Originally Posted by blufeb95
Subaru says that you can run a 5w30 or 5w40 conventional if 0w20 synthetic is not available but you're supposed to use a 0w20 the next oil change, to me that translates to the engine will operate just fine with thicker oil but due to the fuel economy and emissions information we submitted to the government we can't tell you that you're allowed to use them all the time. Plus euro 0w40 runs on the very thin side, usually just over the minimum viscosity necessary to qualify as a 40, so it's more like a thick 30.


A 40 is not a "thick 30" when it meets viscosity requirements of a 40 and not a 30. A 40 is a 40 and a 30 is a 30.

Yeah, but what if it's more of a really super duper thicky 30 and less of a thin 40?
laugh.gif
 
Originally Posted by wemay
Originally Posted by blufeb95
Subaru says that you can run a 5w30 or 5w40 conventional if 0w20 synthetic is not available but you're supposed to use a 0w20 the next oil change, to me that translates to the engine will operate just fine with thicker oil but due to the fuel economy and emissions information we submitted to the government we can't tell you that you're allowed to use them all the time. Plus euro 0w40 runs on the very thin side, usually just over the minimum viscosity necessary to qualify as a 40, so it's more like a thick 30.


A 40 is not a "thick 30" when it meets viscosity requirements of a 40 and not a 30. A 40 is a 40 and a 30 is a 30.

Out of the bottle it's barely a 40 weight, given that it's a 0w40 it'll shear to a 30 pretty quickly, through out most of the OCI it'll be more like a thick 30.
 
I run 0W-40 M1 in the wife's 2018 F350 with the Gasoline engine in it. And in my sons 2006 Toyota P/U with the 2.7 engine.
 
I noticed you said 0W40 reduces oil consumption. Subaru FB25's do use low tension rings. When using a thicker oil with low tension rings, the added thickness can cause the rings to push in the ring valleys (until ring gap is closed) on the piston. Causing actually more oil consumption when compared to using a thinner oil. Ring gap is usually around 0.004" which is the thickness of a piece of paper. It doesn't sound like much to cause oil consumption, but apparently its an issue with low tension rings.
 
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