Oil weight

[Grumpy Bear]

2 hours ago, seamus2154 said:

0/20 along with the trans, and synth rear fluid are all for fuel mileage.....................I also do not use the thin crap they use in the rear diff.  I have not lost any fuel mileage at all. 

Yes it is. 75W90 conforms to the same SAE specification regardless of the base stock so there isn't any 'thin crap' 75W90 and thus a partial explanation of your fuel mileage.  The other is the Ecotec3 motors are saddled with a 207F thermostat and an oil cooler that is integral to the radiator meaning your oil temperature on a nice warm Floridian day is hovering 250-300F. At those temperatures the cSt viscosity of both 20 and 30 oil is within about 1 unit and both under 3 cSt's. That's the second piece of your fuel mileage puzzle. The third is...well it is Wisconsin in winter there. 

[Z45]

Engines are built to use a certain viscosity of motor oil. Today’s advanced engines, built with much tighter tolerances than their predecessors. The clearances between the crankshaft journals and main bearings are tighter, for one. This is purposely done to allow modern engines to use lower-viscosity motor oil, like 0W-20.

[sdeeter19555]

Yes it is. 75W90 conforms to the same SAE specification regardless of the base stock so there isn't any 'thin crap' 75W90 and thus a partial explanation of your fuel mileage.  The other is the Ecotec3 motors are saddled with a 207F thermostat and an oil cooler that is integral to the radiator meaning your oil temperature on a nice warm Floridian day is hovering 250-300F. At those temperatures the cSt viscosity of both 20 and 30 oil is within about 1 unit and both under 3 cSt's. That's the second piece of your fuel mileage puzzle. The third is...well it is Wisconsin in winter there. 

He was probably referring to the new 75w85 they started using...

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[sdeeter19555]

Engines are built to use a certain viscosity of motor oil. Today’s advanced engines, built with much tighter tolerances than their predecessors. The clearances between the crankshaft journals and main bearings are tighter, for one. This is purposely done to allow modern engines to use lower-viscosity motor oil, like 0W-20.

From what I have read, tolerance has almost nothing to do with oil viscosity, at least in the clearances we are talking about in a gasoline engine.

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[seamus2154]

1 hour ago, sdeeter19555 said:

He was probably referring to the new 75w85 they started using...

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Yes, I was. Although I used it on the the first two trucks at different mileages when I saw what it looked like coming out with less than 20k on it, I swtched to Amsoil which I have used for years on my Corvettes and other cars. After 20-30K of Amsoil it still looks beautiful. Although not scientific,  it is clearly better. 

[diyer2]

10 hours ago, Mike GMC said:

When you say "extended change interval" are you suggesting a specific interval, or just not exceeding the oil life monitor?

I still do 3 k mile changes and have forever.

At 3 k miles my oil is plenty dirty.

In summer when I tow my boat, I do 2500 mile changes.

I say again, I use Quaker State Semi-syn,  5W30 Dexos 1 bought at Walmart. Cheapest price.

Fleet filters bought by the dozen at an auto store. I have used fleet filters on  my vehicles for years.

My oil changes cost $20.

 

I met the west district service manger for Ryder truck rental in an RV campground. Their policy was oil is cheap.

I also used to be a heavy equipment operator, same thing, oil and lube are cheap.

A piece of equipment that's in the shop for repairs isn't making money.

 

I will  also add this,

The Caterpillar trained mechanic where I worked didn't go by mileage for oil changes on his vehicles.

He went by gallons of fuel used.

This was a direct result of his Cat schooling and testing they had performed.

He changed his oil every 200 gallons of fuel.

Let;s use my vehicles for an example.

Truck averages 16 mpg. Living in the mountains this is what it gets.

3  k miles divided by 16 = 187.5 gallons.

Wife's car gets 20 mpg.

3 k miles divided by 20 = 150 gallons.

 

You do what makes you happy.

This makes me happy.

 

 

 

 

 

 

 

 

[sdeeter19555]

I did OLM intervals early on, the oil analyzed as still good for continued use. The oil would drain just a dark brown.

But as the truck got miles on it, you could see the oil turn black sooner, so I have started reducing my intervals...I'm down to 5k mile intervals with Mobil 1 5w30.

I do fairly short intervals in my Equinox because the wife does a lot of idling at the bus stop and does the remote start thing quite often. I don't go past 50% on the OLM, which is typically 3k or less...the oil drains with a heavy fuel odor.

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[Mike GMC]

My wife also has an Equinox, a 13.  I follow the OLM on that one with full syn 5w-30.  It is usually less that 1/2 quart low and not quite black yet.  That one has 92000 miles on it now.  My 15 GMC is new to me, I got in January.  I have not changed the oil yet, but at 2500 miles, it's still hard to see on the stick, full and does not smell like fuel.  Judging by the OLM, it will be 7500 to 8000 miles before it says it wants a change.  As long as it stays full and reasonably clean looking, I may let it go that far.  If it starts to look black or the level drops or I smell fuel, I'll change it sooner. Just not sure what weight I will use when I do.

[ESSGUY]

trucks spec 0-20 because of tight tolerances? Corvettes spec up to 0-40, they must have sloppy loose tolerances by that reasoning then? Or maybe the 6.2l in the trucks isnt that similar to the Corvette.

[MaverickZ71]

21 hours ago, garagerog said:

Back in the days of dino only oil GM specifically recommended against the use of 10-40W oil. I believe their reasoning was that the more viscosity modifiers you had to add to oil, the less actual lubricant you have. Additives have no lubricating property on their own, so the addition of more viscosity modifiers, anti-foaming agents, anti-corrosion agents, detergents, et. al. results in a lower percentage of actual lubricant. Synthetic oil by nature resists viscosity break-down, therefore I assume less of a viscosity package is needed.  Just supposition on my part but that's why I believe you see a wider range of accepted viscosity ratings for synthetic oil.   My brother went to the dark side about 3 years ago and bought a 6.4l Hemi Ram to pull his 35 ft. TT, he's told me that 0-40W synthetic is what's called for it and he has trouble finding it locally and so he buys it on Amazon. 0-40W sounds crazy to me, but what do I know.

The General recommended against 10W-40 oil?  Where??  Guess my Pontiac's owner manual is wrong where it says to only use 10W-40 oil, then.  

[MaverickZ71]

5 hours ago, elcamino said:

Engines are built to use a certain viscosity of motor oil. Today’s advanced engines, built with much tighter tolerances than their predecessors. The clearances between the crankshaft journals and main bearings are tighter, for one. This is purposely done to allow modern engines to use lower-viscosity motor oil, like 0W-20.

Tighter tolerances maybe, but with the certain exception of the piston rings clearance to the cylinder walls, which is ridiculously loose (compared to what it used to be in the old days) in order to try to lessen friction to gain any mpg advantage.  Just like any assembly, some of those end up being excessively loose, which explains the blow-by, oil usage, and dirty oil that many of us (especially with extensive idling) experience.  

[Black02Silverado]

21 hours ago, Mike GMC said:

I would think that as well, but the question is, are sacrificing any long term engine life in the name of a few tenths of a mile per gallon?

No, you get the same protection.  In all the used oil analysis I have done running a 0w-20 and 5w-20, the protection is the same as running a 5w-30.  Even when the vehicle called for a 5w-30 and I ran a 5w-20.  My UOA's came back the same for wear.

 

If you really want to know what is going on in your engine a UOA is the way to go.  So many variables like, temp, driving conditions, location like mountains for flat land, close to the coast  with salt air  or in the heat of Arizona summers. Not to mention the colds of the great white north.

[sdeeter19555]

No, you get the same protection.  In all the used oil analysis I have done running a 0w-20 and 5w-20, the protection is the same as running a 5w-30.  Even when the vehicle called for a 5w-30 and I ran a 5w-20.  My UOA's came back the same for wear.
 
If you really want to know what is going on in your engine a UOA is the way to go.  So many variables like, temp, driving conditions, location like mountains for flat land, close to the coast  with salt air  or in the heat of Arizona summers. Not to mention the colds of the great white north.

My only comment is that, while a used OIL analysis can provide some indirect insight into engine condition, a used OIL analysis only tells you how well or not well the oil held up.

Too many times people claim engine condition using UOA, and that is not correct.

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[KARNUT]

I still do 3 k mile changes and have forever.
At 3 k miles my oil is plenty dirty.
In summer when I tow my boat, I do 2500 mile changes.
I say again, I use Quaker State Semi-syn,  5W30 Dexos 1 bought at Walmart. Cheapest price.
Fleet filters bought by the dozen at an auto store. I have used fleet filters on  my vehicles for years.
My oil changes cost $20.
 
I met the west district service manger for Ryder truck rental in an RV campground. Their policy was oil is cheap.
I also used to be a heavy equipment operator, same thing, oil and lube are cheap.
A piece of equipment that's in the shop for repairs isn't making money.
 
I will  also add this,
The Caterpillar trained mechanic where I worked didn't go by mileage for oil changes on his vehicles.
He went by gallons of fuel used.
This was a direct result of his Cat schooling and testing they had performed.
He changed his oil every 200 gallons of fuel.
Let;s use my vehicles for an example.
Truck averages 16 mpg. Living in the mountains this is what it gets.
3  k miles divided by 16 = 187.5 gallons.
Wife's car gets 20 mpg.
3 k miles divided by 20 = 150 gallons.
 
You do what makes you happy.
This makes me happy.
 
[emoji4]
 
 
 
 
 
 
 

That’s funny. I’m retired from an equipment business. We built, operated attachments for all kinds of prime movers Cat included. We are OEM for several. If we or any of our costumers change their oil every 200 gallons of fuel, that would be every to every other day. It was 200 HRs to 400 HRs depending on dust or synthetic or not. Extreme duty on vehicles rarely call for 3K service anymore. No cat, John deer, or any equipment rep is going to recommend 200 gal fuel burn oil changes. They’d be laughed off the job site.


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[diyer2]

Let me clarify Karnut.

Oil changes at 200 gallons of fuel were not for equipment.

This was his choice from oil samples he seen for his vehicles.

Was he going overboard?

Probably.