I hate to ask another oil question, but...
... does anyone know where I can buy CJ-4 in 10-30W in the PA/NJ/DE area. I have been to every auto parts store in my area and have found nothing but 15-40W.
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Re: I hate to ask another oil question, but...
Any of the stores that stock the 15W-40 are capable of special ordering it for you. -
Re: I hate to ask another oil question, but...
Why do you want 10W-30 instead of 15W-40?
DukeComment
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Re: I hate to ask another oil question, but...
Duke,
It's a fresh rebuild and the shop that did the machine work told me to run 10W-30. I'm guessing from your question that 15W-40 is acceptable? As you might imagine, the car will likely never see a cold weather start.Comment
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Re: I hate to ask another oil question, but...
One of my friends special ordered a case of 10-30 last week and we will split it. I switched to CJ-4 15-40 a few months ago and my oil pressure was WAY too high. He has the same complaint/issue with too much oil pressure with 15-40.Comment
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Re: I hate to ask another oil question, but...
There's little difference, especially if you don't normally do cold starts in sub-freezing temperatures.
Before I switched all my cars to 15W-40 C-category oil I used dual rated 20W-50. I never saw a meaningful difference in oil pressure on any of my cars.
DukeComment
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Re: I hate to ask another oil question, but...
Go here for a simple explanation:
The first number is not critical for most of us, as we won't be running our engines in cold weather.
The second number designates the oil's viscosity (shear-rate) at 210 degrees Fahrenheit (this is your engines "ideal" average oil temp when at op temp). You'll notice a significant difference in shear rates @ 210 deg. F. between the "30" and "40" weight oils. This lower film shear strength translates into better mileage and more power delivered to the flywheel (and not converted to heat) during shear of the oil when it is flowing or providing film strength on bearings. Try this simple experiment which demonstrates how shear force is converted to heat: take an ordinary plastic bag, like you get from the supermarket. Tear it in two pieces by stretching it until it tears. Your hands should feel slightly warm after you do this.
Another thing to keep in mind, is that all non synthetic motor oils of a given brand are blended from the same base stock. An additive package is blended in which, among other things, gives it its viscosity characteristics. The wider the viscosity range in a multi-vis oil, the more additive is needed to achieve the range. This means more additive, less oil base stock. Many people prefer "straight weight" oil for this reason. In your case, a "straight" 30 weight CJ oil would be appropriate. Use the 10W-30 or the straight 30 weight. In fact, order a truckload of 10W-30 and start a list for a group purchase at a discount. Put me at the top of the list, because I'll be ordering the 10W-30 from my local parts dealer very shortly.
JoeLast edited by Joe C.; May 12, 2009, 05:51 AM.Comment
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Re: I hate to ask another oil question, but...
As an ironic side to this, I too use the 15w-40 and, as I have reported before, I am plagued by a leaky 80# oil pressure gauge. When I first start up, the gauge is pegged and only relaxes to say about 65#'s when warm or running down the road w/i the posted speed limit. My gauge does not leak when I drive normal (sort of), but if I wind it up to red line a few times, I get a wet E-Brake handle. I've taken to stuffing a rag up by the gauge for short drives until I decide what I will do with it, i.e. pinch off the line or change out the gauge when I feel up to it.
Stu FoxComment
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Re: I hate to ask another oil question, but...
Is there a significant increase in oil pressure with a 15W-40 versus a
10W -30?Comment
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Re: I hate to ask another oil question, but...
The Internet is full of "excessive oil pressure" stories with higher SAE viscosity grades. As I said before, a decade ago I used dual-rated 20W-50 in the mild California coastal climate I live in, and none of my cars ever showed "excessive oil pressure". When I switched to C-category 15W-40 I saw no reduction of oil pressure.
The SAE viscosity grades have considerable overlap, so at 212F the absolute viscosity of an SAE grade 40 may not be much higher than SAE 30 depending on the blend of base stocks.
In the engine oil article I wrote in The Corvette Restorer one of the links I referenced has a chart that shows the full range and overlap of the various SAE viscosity grades for both engine and gear oil, which use different viscosity numbers to differentiate them. Engine oils use zero to 60 and gear oils use 70 to 140.
DukeComment
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Re: I hate to ask another oil question, but...
I've owned/driven this 66 425 HP car for over 25 years and I KNOW exactly what the oil pressure range was for all those years. I also know that when I switched from 10-30 to 15-40 CJ-4, the pressure increased, a lot.
Cold start/idle is now just under #70 and hot (200*) idle is around 45*.
Hot idle with conventional 10-30 was around #25.
I was very surprised that just an increase of that amount in viscosity would produce that kind of pressure increase. I have to wonder if it has something to do with the CJ-4? I don't know near enough about oil to carry on an intelligent conversation about it's makeup but I do know that I don't like or want that kind of oil pressure in my engine. I don't want my distributor bushings and shaft to pay the price for this.Comment
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Re: I hate to ask another oil question, but...
Just think of how much internet ink would have been saved if Chev have not installed an oil pressure, coolant temperature or battery charge gauges in Corvettes.
We'd all live in blissful innocence/ignorance and our engines would live happily in spite of themselves.
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Re: I hate to ask another oil question, but...
That's why a lot of cars just have warning lights, nowadays. Last week I evaluated and test drove a MINI for a friend - no oil pressure gage, temp gage, or voltmeter - just warning lights and a ton of "comfort and convenience" bells and whistles. The "fuel gage" consisted of ten LEDs that progressively go out as fuel is consumed - different that what I am accustomed to, but equally functional.
GM trucks have a better gage suite than my '91 MR2. Back when the car was new I asked some Toyota marketing execs about this, and they told me about all the letters they got about too much to too little oil pressure when Toyotas had oil pressure gages. So they just eliminated the gage, and replaced it it a low pressure warning light on all models.
C-category oils are blended from the same base stocks as S-category but the blend of viscosities and VI improvers varies with the desired final SAE viscosity range.
If you look at owner's manuals from the sixties and seventies, many say straight SAE 30 is okay for cold starts down to 40 F, so I could use it year round in my climate, but the lower cold viscosity of a multi-vis blend does reduce oil flow resistance and probably cold oil pressure.
High cold oil pressure means the bypass circuit can't flow enough oil even when the valve is full open, but most engines will not exceed normal hot oil pressure once the oil reaches normal operating temperature which is something in the range of 180-230 F for normal road driving.
Of course the above assumes that the oil pump and relief spring are OE equivalent, which is often NOT THE CASE since every "engine builder" on the planet seems to want to install a high volume/high pressure oil pump regardless of what was OE, and this usually turns out to be the source of most "high oil pressure" problems.
DukeLast edited by Duke W.; May 12, 2009, 11:25 AM.Comment
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Re: I hate to ask another oil question, but...
Unfortunately those gaugeless cars that are only equipped with "warning" lights won't give you much warning when there is a problem. By the time they read an out of range situation the horse has already left the barn. Maybe that's why they refered to them as idiot lights over the years.Comment
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Re: I hate to ask another oil question, but...
I have to admit I was living in ignorant bliss with my oil pressure gauge disconnected from the mid-70's until last year. I also recall the days before that when I would see hot idle in traffic at around 15# and would consider pulling over. Having found the oil drops on my E-Brake handle that caused me to disconnect it was a god send.
Stu FoxComment
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