Simplest way to lower viscosity? Mobil 15w50

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The big block in my Chevy truck is enjoying Mobil 1 15W50. The oil has maybe 2000 miles on it. These 496/8.1L engines are known for oil consumption. This oil with a lower temp thermostat stopped consumption totally. I thought I would have still lost a quart or so by now and I could have topped off with a 0W20 to help thin it out for winter, but no.

Kind of seems like a waste to drain out the oil. At what temp is 15w50 going to be too thick? I'd guess cold starts under 30 degrees aren't ideal.

Any acceptable ways to thin it down some? Use the remote start more? Ha.
 
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it's fine for those temps. I wouldn't worry until it gets to below 10f. And i didn't know remote start was a thing during the 8.1's existence. Is it an aftermarket system or something. I thought that was an option beginning with the generation after that.
 
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The current flavor of 15W-50 becomes too viscous to be useful at about -10F. Above that, it flows reasonably well. In years past, it would flow reasonably well to about -30F.

In PA, it will probably be OK all winter, as long as you let the engine warm up a bit before driving off.
 
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The big block in my Chevy truck is enjoying Mobil 1 15W50. The oil has maybe 2000 miles on it. These 496/8.1L engines are known for oil consumption. This oil with a lower temp thermostat stopped consumption totally. I thought I would have still lost a quart or so by now and I could have topped off with a 0W20 to help thin it out for winter, but no.

Kind of seems like a waste to drain out the oil. At what temp is 15w50 going to be too thick? I'd guess cold starts under 30 degrees aren't ideal.

Any acceptable ways to thin it down some? Use the remote start more? Ha.
why bother?

just keep using it, the pour point is -39C, how cold does it get where you live?

 

Gasbuggy

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Your Manual should tell you how low you can go with a 15W

Unfortunately I don't have one to look at but I've read complaints GM just slapped the same specs as the LS in the book.
it's fine for those temps. I wouldn't worry until it gets to below 10f. And i didn't know remote start was a thing during the 8.1's existence. Is it an aftermarket system or something. I thought that was an option beginning with the generation after that.

It has an Avital remote start and I'm impressed with it. It replaces the stock key fob for the doorlocks and works from an incredibly far distance.



Good to know I can run this oil at lower temps than I figured.
 
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The current flavor of 15W-50 becomes too viscous to be useful at about -10F. Above that, it flows reasonably well. In years past, it would flow reasonably well to about -30F.

In PA, it will probably be OK all winter, as long as you let the engine warm up a bit before driving off.
Exactly. Mixing a 15wXX with something less than that may “thin” out the operating temp viscosity, but the parts of the Mobil that are 15wXX do not “blend down” to say a 7.5wXX or 12wXX.

If you want better cold weather performance than a 15w50 offers, you’d need to drain it and fill with a 10wXX oil.
 
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You can usually find a pdf manual online for your vehicle.
Screenshot 2022-11-13 at 23-20-17 oil grade owners manual - Google Search.jpg
 

ZeeOSix

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Which does not necessarily relate to nor result in a particular winter rating.
Yep ... an SAE 15W rating/grade is specified as a max CCS dynamic viscosity of 7000 cP at -20C, a long way warmer than that -39C pour point which has nothing to do with dynamic viscosity. The dynamic viscosity at -39C would be way more than 7000 cP in the CCS.
 

Shel_B

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The current flavor of 15W-50 becomes too viscous to be useful at about -10F. Above that, it flows reasonably well. In years past, it would flow reasonably well to about -30F.

In PA, it will probably be OK all winter, as long as you let the engine warm up a bit before driving off.
@Cujet, would you be kind enough to explain why that is? I'd have thought newer oils would have better flow characteristics.
 
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Exactly. Mixing a 15wXX with something less than that may “thin” out the operating temp viscosity, but the parts of the Mobil that are 15wXX do not “blend down” to say a 7.5wXX or 12wXX.

If you want better cold weather performance than a 15w50 offers, you’d need to drain it and fill with a 10wXX oil.

You won't know where you end up with the winter rating, but it does reduce the cold viscosity as it does hot.
 

dnewton3

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He lives in PA; it can get fairly cold there in short bursts ...
I'd say run a 10w-40 in winter. Or even a 10w-30.

I'd rather suffer a bit of oil consumption rather than poor lubrication at start up and the possilbe permanent side effects thereof ...
 

ZeeOSix

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The lowest temp 15W should possibly be used is -4F (-20C) per SAE J300, but many car makers back that off some to be safe. If I was running a 15W I'd say 20F (-7C) would be a safe low temp use limit.
 
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The big block in my Chevy truck is enjoying Mobil 1 15W50. The oil has maybe 2000 miles on it. These 496/8.1L engines are known for oil consumption. This oil with a lower temp thermostat stopped consumption totally. I thought I would have still lost a quart or so by now and I could have topped off with a 0W20 to help thin it out for winter, but no.

Kind of seems like a waste to drain out the oil. At what temp is 15w50 going to be too thick? I'd guess cold starts under 30 degrees aren't ideal.

Any acceptable ways to thin it down some? Use the remote start more? Ha.
I started 10W40 at -42c.
 
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