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Oil Viscosity - What are people using, and why, after all these years?


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Hello All,

This is my first post to these forums and, sincerely, I am not trying to start any sort of "oil war," but just to see what people are chosing to do and why.

I very recently acquired my first Cadillac, a 1989 Sedan de Ville with 96K, that's in absolutely incredible condition for its age. I have been using it as my daily driver and plan to continue doing so. In these early days of ownership I've been poring over the Owner's Manual and doing all the "baseline fluid changes." I've had the transmission serviced with a new filter and fluid by my local transmission shop. The radiator was changed just a few months before purchase, so I haven't changed coolant yet. The oil (5W30) and filter as well as the air filter were changed yesterday.

The Owner's Manual specifies 10W30 as the "default" motor oil with 5W30 being "allowed" if you anticipate temperatures below 60° F and encouraged if the temperature is supposed to be significantly lower.

However, oil technology has evolved, pretty radically, since 1989. We were at API service SG/CC and have come all the way up to SN now (and SN is wholly backward compatible with all prior API service levels for gasoline engines). The ILSAC was pretty much unknown then and now GF-5 has become "the standard for the world" as far as gasoline motor oils go.

I'm also old enough to remember when the "low end" of multi-viscosity motor oils was 10W and 5W or 0W was nowhere to be seen.

My understanding regarding how engineers determine the appropriate "upper number" for a given car is dependent on physical dimensions and tolerances inside the engine. That weight of oil is the maximum viscosity, at full operating temperature, that allows the ideal flow at all points in the engine where it needs to flow.

The lower number, though, is a different issue. That tends to be determined by flow needs when the engine and/or the ambient temperature is cold. Mind you, cold oil is much thicker than it ever will be when fully hot. The upper number tells you that a multi-viscosity motor oil acts like the stated weight when hot, and hot 30W is "thinner" than cold 5W.

Yeesh, that was a lot of intro in an effort to prevent any sort of "oil war."

What I'm wondering is whether it has become common for people to "go lower" on the "lower number" of their multi-viscosity oil as the years have gone by. In the Rolls-Royce world, the original recommended motor oil for the cars of the 1970s was 20W50, but virtually no one uses that anymore. The preference has trended toward a "lower number" of 10 with many using 5 and some 0. The improvement of flow "when cold" is obvious and since multi-viscosity oils rapidly begin behaving as their "higher number" weight oils would as they warm this appears to be a reasonable way to go.

So, what multi-viscosity weight oil are people using in the 4.1, 4.5, and 4.9 non-Northstar engines?

Brian

Brian

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Bri the Tech Guy   http://britechguy.com
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The 4.1, 4.5, 4.9 engines were spec'd to use 10W-30 That being said, the ZDP (antiwear additive) has been reduced in the last 20 years. the 4.x engines with their distributor gears, need extra antiwear additive. I would use Shell Rotella 10W-30 oil - it is a diesel oil that has more antiwear additives than standard 10W-30. If you can't find Rotella 10W-30, the next best thing is the Rotella 15W-40 oil, the Mobil 15W-40 diesel oil, or Chevron Delo 15W-40 Diesel oil. Do not use 5W-30 oil in your car. You can also buy GM Engine Oil Supplement (EOS) from GM and add a few ounces to standard 10W-30 oil. EOS has a high concentration of ZDP and is used for engine break in. A couple of ounces of EOS added to the standard 10W-30 oil will bring the ZDP back up to the levels where they were 25 years ago.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The 4.1, 4.5, 4.9 engines were spec'd to use 10W-30 That being said, the ZDP (antiwear additive) has been reduced in the last 20 years. the 4.x engines with their distributor gears, need extra antiwear additive. I would use Shell Rotella 10W-30 oil - it is a diesel oil that has more antiwear additives than standard 10W-30. If you can't find Rotella 10W-30, the next best thing is the Rotella 15W-40 oil, the Mobil 15W-40 diesel oil, or Chevron Delo 15W-40 Diesel oil. Do not use 5W-30 oil in your car. You can also buy GM Engine Oil Supplement (EOS) from GM and add a few ounces to standard 10W-30 oil. EOS has a high concentration of ZDP and is used for engine break in. A couple of ounces of EOS added to the standard 10W-30 oil will bring the ZDP back up to the levels where they were 25 years ago.

Kevin,

Thank you for your input. I would suggest you take the time to read the API and ILSAC specs regarding current motor oils. There is nothing to indicate that whatever has replaced ZDDP is not equally effective, and this is borne out by the testing that's necessary to receive the current API and ILSAC specification approvals.

The whole ZDDP concern appears to be as much the "tempest in a teapot" that parallels the proclamations about the death of engines when unleaded gasoline was mandated.

When it comes to what an oil is good at doing, or not doing, I will accept what the certifying bodies tell me above all else. I always suggest that people do their own research so that they can make an informed decision they are comfortable with. That decision need not be the same as mine.

Brian

Brian

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Bri the Tech Guy   http://britechguy.com
britechguy@gmail.com   (540) 324-5032
"If it's got you screaming, I'll help you stop!!"
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The 4.1, 4.5, 4.9 engines were spec'd to use 10W-30 That being said, the ZDP (antiwear additive) has been reduced in the last 20 years. the 4.x engines with their distributor gears, need extra antiwear additive. I would use Shell Rotella 10W-30 oil - it is a diesel oil that has more antiwear additives than standard 10W-30. If you can't find Rotella 10W-30, the next best thing is the Rotella 15W-40 oil, the Mobil 15W-40 diesel oil, or Chevron Delo 15W-40 Diesel oil. Do not use 5W-30 oil in your car. You can also buy GM Engine Oil Supplement (EOS) from GM and add a few ounces to standard 10W-30 oil. EOS has a high concentration of ZDP and is used for engine break in. A couple of ounces of EOS added to the standard 10W-30 oil will bring the ZDP back up to the levels where they were 25 years ago.

Kevin,

Thank you for your input. I would suggest you take the time to read the API and ILSAC specs regarding current motor oils. There is nothing to indicate that whatever has replaced ZDDP is not equally effective, and this is borne out by the testing that's necessary to receive the current API and ILSAC specification approvals.

The whole ZDDP concern appears to be as much the "tempest in a teapot" that parallels the proclamations about the death of engines when unleaded gasoline was mandated.

When it comes to what an oil is good at doing, or not doing, I will accept what the certifying bodies tell me above all else. I always suggest that people do their own research so that they can make an informed decision they are comfortable with. That decision need not be the same as mine.

Brian

The statements I made in my earlier post were from a GM powertrain engineer who used to frequent this board. He had direct expierence with the design and development of the Northstar engine as well as the 4.X engines. Engines today have roller cam followers, and no distributors so they require less antiwear additives. Your post asked what people were using and why so I responded.

This was discussed several years ago and everyone on this board got an education in oils from the GM Powertrain engineer. It's to bad the information is not in the archives anymore.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Kevin,

I am familiar, intimately familiar, with all this from several venues. I have promised that I will not start nor engage in an "oil war" and I won't. At the same time, any one man, regardless of who that one man is, does not get to make definitive statements that conflict with the certifying bodies and then that becomes gospel. I have posted the following elsewhere, but will post it here so that others may do their own reading and come to their own conclusions:

Reading through the API & ILSAC motor oil standards/specifications for current (API SN/ILSAC GF-5)
oils and the preceeding specs should put anyone's mind to rest about the suitability of currently available
motor oils for use in older car engines. On the API website, they explicitly state, "For automotive gasoline
engines, the latest engine oil service category includes the performance properties of each earlier category.
If an automotive owner's manual calls for an API SJ or SL oil, an API SM oil will provide full protection."
[see: http://www.api.org/certification-programs/engine-oil-diesel-exhaust-fluid/service-categories]
For oils for gasoline-powered engines, each and every specification meets or exceeds the performance of all
of its predecessors. This means that there has been a continuous improvement in lubrication performance
and that oils meeting current specifications are far more than "adequate" for older engines.

API Materials:

Motor Oil Matters Guide (2013), "Which Oil is Right for You?" -
http://www.api.org/certification-programs/engine-oil-diesel-exhaust-fluid/~/media/Files/Certification/Engine-Oil-Diesel/Publications/MOM_GUIDE_ENGLISH_2013.pdf

Full API 1509 Spec - 17th Ed - September 2012 (Includes ILSAC GF-5 Spec in Appendix Q)
http://www.api.org/certification-programs/engine-oil-diesel-exhaust-fluid/~/media/Files/Certification/Engine-Oil-Diesel/Publications/150917editionfinal.ashx

Oil Licensing and Certification Technical Bulletin - http://www.api.org/certifications/engineoil/new/upload/1509techbull1complete.pdf


ILSAC Final GF-5 Spec:
http://www.gf-5.com/uploads/File/ILSAC_GF-5_Dec-22-09_final.pdf


and, from the Mobil Oil Q&A Site:

On needing to Mix Oils for ZDDP Levels:
http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/ZDDP_Levels_Classic_Cars.aspx
I find it interesting that even on this "answers" page the statement is made that a
particular one of their oils, "already contains a higher level of ZDDP (1000 ppm) that
could benefit your flat tappet engine." [emphasis on that could is mine]. I have yet
to find a single manufacturer who states either "will" or "does," but instead couches
the statements in ways such that the preconceived notion is addressed.

On Zinc & Phosphorus Levels:
http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Zinc_in_Engine_Oils.aspx

On Purported "Removal" of ZDDP from Motor Oils:
http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Zinc_Motor_Oils.aspx

Mobil Oil Product Table, including Zinc & Phosphorus Levels:
http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf

I'm still very curious to know if the cohort has generally stuck with using 10W30 or if there has been a move toward 5W30. Since the owner's manual states:

"SAE 10W-30 (SAE 5W-30 is all right [sic] if it's going to be colder than 60°F. (16°C) before your next oil change). Whein it's very cold, below 0°F (-18°C.), you should use SAE 5W-30."

In Virginia (and quite a bit of the US) that would mean that 5W-30 would be appropriate for far more of the year than 10W-30, and lubricants have vastly improved since 1989.

Brian

Edited by guyslp

Brian

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Bri the Tech Guy   http://britechguy.com
britechguy@gmail.com   (540) 324-5032
"If it's got you screaming, I'll help you stop!!"
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You use the oil you want to... I use the oil I want to.

No arguments that way.

In the end, that's what we all do.

I'm just glad that the bulk of the cars in the soon-to-be-culled fleet of seven take either 5W30 (4 or 5, Cadillac most of the year included) or 10W40.

Of course, I still have to lay in the supply of full synthetic for the 1999 and later cars and conventional for the older ones.

Brian

Brian

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Bri the Tech Guy   http://britechguy.com
britechguy@gmail.com   (540) 324-5032
"If it's got you screaming, I'll help you stop!!"
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0W-30 100% Synthetic in both my CTS4 and my Sierra Denali AWD 6.2L, been using 0W-30 since if first became available back in 1996.

Been using 100% Synthetic oil )not Mobil 1) since about 1975ish.....Never used anything else. All the lubes in my vehicles are synthetic, I change them out ASAP.

Fyi

The W in 5W-30 motor oil stands for Winter and indicates the oil meets or exceeds certain criteria for good low-temperature performance. Motor oil with SAE viscosity grade 5W-30 behaves like an SAE 43 oil at high temperatures and SAE 5W oil at low temperatures, providing the necessary fluidity for rapid starts and efficient engine operation/protection at low temperatures. So a 0W, 5W and 10W-30 are all 30 wt oils, the difference is in their cold flow properties.

An oils cold-temperature performance refers to its ability to flow when the engine is cold, or below typical operating temperature (212 F / 100 C), and not simply to what feels cold to humans - warm summer days are also cold to an engine. Startup lubrication is directly affected by a lubricants cold-flow ability, and the impact is felt at higher temperatures than most consumers would think.

PS - Been in the lube business for over 30 yrs.......

Edited by Z15
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Kevin,

I am familiar, intimately familiar, with all this from several venues. I have promised that I will not start nor engage in an "oil war" and I won't. At the same time, any one man, regardless of who that one man is, does not get to make definitive statements that conflict with the certifying bodies and then that becomes gospel.

Brian

One man does get to make statements when he is directly involved in the business. Standards are a compromise - he was well aware of the compromises in the standard and made the recommendation to this board that we use the diesel oil in the 4.X engines. That's good enough for me. If you'd rather use 10W-30 or 5W-30 oil in your car - that is your choice.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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