I just happened recently to be reading the manuals on-line from a diverse group of GM cars from the 50's and 60's and noticed that 10W-30 was the heaviest oil recommended in any of them. Contrary to the factory recommendations, however, I remember my dad in the 1960's running 10W-40 in virtually all of his cars (a 1955 Buick, a 1957 Oldsmobile, a 1962 Cadillac and a 1967 Cadillac) and that viscosity also seemed to be the most popular at gas stations then based on the display cans I remember seeing. Although we lived in Kansas City, we traveled a lot throughout Missouri, Arkansas and other parts of the South and whichever car we had and whatever state we were in, whenever they would check the oil and it would be a quart low, they would always say something like "you want 10W-40, right?" Also, I used to go with him to change the oil in those cars at a local Mobil gas station in Kansas City and they always brought out 10W-40 without there even being any discussion about it. I also remember seeing cans of oil at the local Cadillac dealer (Roach Cadillac) and the only ones I recall all said 10W-40. So, I was really astounded to see that in the actual 1955 Buick manual, 10W-20 (that's not a typo) was recommended for use in all temperatures over -10 degrees Fahrenheit and for under -10 degrees, 5w-20 was the recommendation. I had been thinking that thicker oil was recommended in the past because engine tolerances were looser back then in comparison to today's engines where 5W-20 and 5W-30 is commonly specified but based on those manuals, thicker oil wasn't recommended back then after all. So, I guess I have 2 questions really. First, am I correct that 10W-40 was the most popular oil viscosity in general use for most cars back in the 1960's? Second, if I am correct about that, how in the world could that be the case when GM (at that time clearly the world's leading car manufacturer) wasn't recommending that viscosity? If I'm right, then a lot of people were using the wrong stuff in an awful lot of cars and it really mystifies me how so many people could have been acting contrary to what was plainly printed in their owner's manuals? Historical delusions and misconceptions are things that have always interested me. All thoughts and perspectives will be appreciated.
why was 10W-40 so popular back in the 1960's?
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my dad ran 10w40 for decades. im my circle of friends 20w50 was the norm
I think that 10w-40 was the first multigrade.
Here in OZ 10w-40's and 20w-40's were the norm through to the 80's for our locally built cars. Naturally there was always/is the standard 15w-40 HDDO.
I think 10w-40 is still the current grade for one locally built turbo l6 engine still in production.
Now with most engines coming into OZ from the USA over the last 8 years or so, the oils being spec'd are getting thinner.
I'm personally running a 10w-30 which was the only specified grade before the change to 5w-30 in my 2006 LS2, and that's the absolute thinnest oil I've ever run in any engine in my life.
Except for straight SAE 30 lawn mower oil.
I think 10w-40 is still the current grade for one locally built turbo l6 engine still in production.
Now with most engines coming into OZ from the USA over the last 8 years or so, the oils being spec'd are getting thinner.
I'm personally running a 10w-30 which was the only specified grade before the change to 5w-30 in my 2006 LS2, and that's the absolute thinnest oil I've ever run in any engine in my life.
Except for straight SAE 30 lawn mower oil.
Then as now, many of us thought that we knew more than the OEMs did about the appropriate grade to use.
Most of us saw the forty as an oil that would provide better high temperature protection and it never occured to us that the greater proportion of VIIs required to make a 10W-40 as opposed to a 10W-30 might be a problem.
It also never occurred to us that a 10W-30 provided all of the high temperature viscosity required.
10W-40 was pretty much the lightest oil I used from the early 'eighties up through 1997.
Back through the 'eighties, 10W-40 was widely recommended for Japanese brands, while European ones often called for 20W-50 as the summer fill.
What was wrong with the American manufacturers?
Why would they recommend something as thin as a 10W-30 for the heat of summer?
In 1997, we bought a new Aerostar for which 5W-30 was recommended.
I guess that I experienced an enlightenment, and began using what I'd always considered this overly thin grade.
Worked just fine for the 175K we put on the thing, just as it worked fine in our 207K '97 Accord and our 175K '99 Accord.
I could never quite bring myself to use a thirty in our old '86 Civic Wagons, both of which were retired after 200K+.
Many of us felt that 10W-30 was too thin.
We were probably mistaken.
Most of us saw the forty as an oil that would provide better high temperature protection and it never occured to us that the greater proportion of VIIs required to make a 10W-40 as opposed to a 10W-30 might be a problem.
It also never occurred to us that a 10W-30 provided all of the high temperature viscosity required.
10W-40 was pretty much the lightest oil I used from the early 'eighties up through 1997.
Back through the 'eighties, 10W-40 was widely recommended for Japanese brands, while European ones often called for 20W-50 as the summer fill.
What was wrong with the American manufacturers?
Why would they recommend something as thin as a 10W-30 for the heat of summer?
In 1997, we bought a new Aerostar for which 5W-30 was recommended.
I guess that I experienced an enlightenment, and began using what I'd always considered this overly thin grade.
Worked just fine for the 175K we put on the thing, just as it worked fine in our 207K '97 Accord and our 175K '99 Accord.
I could never quite bring myself to use a thirty in our old '86 Civic Wagons, both of which were retired after 200K+.
Many of us felt that 10W-30 was too thin.
We were probably mistaken.
SAE30 was recommended in a lot of owners manuals back then and 10W-40 is basically a 30 weight oil.
MolaKule
Staff member
I think the general thinking at the time was that the heavier cuts of Group I used in the then 10W40 had a higher film strength since additive technology didn't have the advantages we have now.
My Dad's '54 Buick with a Big Block, however, recommended 20W20 and he ran this year round to about 150,000+ miles. Never had an engine problem. He did have to have the tranny rebuilt at about 80,000 miles.
He traded it off for a '62 Impala with 283 SB and PowerGlide. We then ran primarily Pennzoil 10W30. I inherited that one when he purchased a 1967 Impala with a 327.
Except for an alternator replacement, I had no problems with the '62 Impala. That 283 in my view was one of GM's better engines with 18 MPG on the highway.
My Dad's '54 Buick with a Big Block, however, recommended 20W20 and he ran this year round to about 150,000+ miles. Never had an engine problem. He did have to have the tranny rebuilt at about 80,000 miles.
He traded it off for a '62 Impala with 283 SB and PowerGlide. We then ran primarily Pennzoil 10W30. I inherited that one when he purchased a 1967 Impala with a 327.
Except for an alternator replacement, I had no problems with the '62 Impala. That 283 in my view was one of GM's better engines with 18 MPG on the highway.
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Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
10W-40 is basically a 30 weight oil.
What?
Both of our 1.6 japanese motors...which run super super tight in the topend...spec 10w40 if the temps go over 86F.
The way I look at it, they were worried about shearing more than anything.
Those old multiweight oils had to shear down pretty fast.
The way I look at it, they were worried about shearing more than anything.
Those old multiweight oils had to shear down pretty fast.
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
For several years in the 60s I used 10-40. It made for very hard starting and clacky engines in the cold temps of Maine. I finally changed to a st 20wt then in 78 I switched to 5-20 M1. That took the lifter clacky out of OHV lifters of that era.
Originally Posted By: Volvohead
. . . because that's what Sears had on sale the most back then.
And as MolaKule hinted, if 10w-30 was good, 10w-40 just had to be "better". That's honestly what a lot of average Joe's thought before oiling up the family Galaxie.
Oh, yeah. 10w-30 was the hot ticket in the '50's. When 10w-40 came out, it was promoted as the "premium" product. They could charge a little more for it and did. Exxon (Enco, back then) sold single weights in a white can, 10w-30 in a silver can and 10w-40 Uniflo in a gold can. Of course it was better. I thought my 1965 Impala ran soooo much better with 10w-40. I hope I've learned something in 45 years.
. . . because that's what Sears had on sale the most back then.
And as MolaKule hinted, if 10w-30 was good, 10w-40 just had to be "better". That's honestly what a lot of average Joe's thought before oiling up the family Galaxie.
Oh, yeah. 10w-30 was the hot ticket in the '50's. When 10w-40 came out, it was promoted as the "premium" product. They could charge a little more for it and did. Exxon (Enco, back then) sold single weights in a white can, 10w-30 in a silver can and 10w-40 Uniflo in a gold can. Of course it was better. I thought my 1965 Impala ran soooo much better with 10w-40. I hope I've learned something in 45 years.
Originally Posted By: Merkava_4
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Who cares what it averages out to? At normal operating temp (100C), 10w-40 is a 40 grade and SAE30 is a 30 grade. And at very cold start up (-25C), 10w-40 pumps better than SAE30.
By the same token you could say that a 30 grade is really a 20 grade or even a 10 grade "in between full cold and full hot," but so what? The SAE grading system (the second number after the W) refers to a viscosity range at 100C, not below it, and not above it.
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Who cares what it averages out to? At normal operating temp (100C), 10w-40 is a 40 grade and SAE30 is a 30 grade. And at very cold start up (-25C), 10w-40 pumps better than SAE30.
By the same token you could say that a 30 grade is really a 20 grade or even a 10 grade "in between full cold and full hot," but so what? The SAE grading system (the second number after the W) refers to a viscosity range at 100C, not below it, and not above it.
Vehicles in those days were neither designed nor manufactured to deliver 300,000 or 400,000 miles.
So at 60,000 miles in your Ford Fairlane 500, you might see some oil use.
100,000 miles was often a good time to think about new rings and maybe an overbore.
So 10W-40 made sense in lessening oil usage until it was time for a rebuild.
So at 60,000 miles in your Ford Fairlane 500, you might see some oil use.
100,000 miles was often a good time to think about new rings and maybe an overbore.
So 10W-40 made sense in lessening oil usage until it was time for a rebuild.
My dad was a Quaker State fan in the 60's-80's. You could tell by the names what the marketing intent was. 10W-30 was called "Super Blend" and 10W-40 was called "DeLuxe." He used 30 in the winter and 40 in the summer. I got the 72 Catalina with about 90,000 miles on it and sold it at 212,000. I used mostly Castrol 10W-40 (I fell for their advertising in the 80's vis-a-vis resistance to thermal breakdown.). The car was not an oil consumer. I did not have to add make up oil in the 3,000 mile OCI's I used to do.
10W-40 for V-8's was common here in the 80's and 15W-50 was often used for four cylinders.
We've learned a lot since then, haven't we?
10W-40 for V-8's was common here in the 80's and 15W-50 was often used for four cylinders.
We've learned a lot since then, haven't we?
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Who cares what it averages out to? At normal operating temp (100C), 10w-40 is a 40 grade and SAE30 is a 30 grade. And at very cold start up (-25C), 10w-40 pumps better than SAE30.
By the same token you could say that a 30 grade is really a 20 grade or even a 10 grade "in between full cold and full hot," but so what? The SAE grading system (the second number after the W) refers to a viscosity range at 100C, not below it, and not above it.
Those are multi-viscosity oils. A 10W-40 is not a 40 weight when cold and after about 2000 miles, it's sheared down to a 30 weight when hot. At some unknown temperature, a 10W-40 and an SAE30 will be at the same viscosity.
Originally Posted By: Merkava_4
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Who cares what it averages out to? At normal operating temp (100C), 10w-40 is a 40 grade and SAE30 is a 30 grade. And at very cold start up (-25C), 10w-40 pumps better than SAE30.
By the same token you could say that a 30 grade is really a 20 grade or even a 10 grade "in between full cold and full hot," but so what? The SAE grading system (the second number after the W) refers to a viscosity range at 100C, not below it, and not above it.
Those are multi-viscosity oils. A 10W-40 is not a 40 weight when cold and after about 2000 miles, it's sheared down to a 30 weight when hot. At some unknown temperature, a 10W-40 and an SAE30 will be at the same viscosity.
Originally Posted By: Merkava_4
Those are multi-viscosity oils. A 10W-40 is not a 40 weight when cold
But the "40" has nothing to do with cold. The "40" is only in reference to viscosity at 100C temperature.
A 10w-40 is a 40 grade when at 100C, just like SAE30 is a 30 grade at 100C.
Those are multi-viscosity oils. A 10W-40 is not a 40 weight when cold
But the "40" has nothing to do with cold. The "40" is only in reference to viscosity at 100C temperature.
A 10w-40 is a 40 grade when at 100C, just like SAE30 is a 30 grade at 100C.
Originally Posted By: Merkava_4
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Merkava
One would think that with the years you've spent here osmosis would have occurred and you'd have learned at least something however by the looks of the above posts your dermis isn't allowing anything thru.
They are good for a laugh though. And for that I thank you.
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Merkava
One would think that with the years you've spent here osmosis would have occurred and you'd have learned at least something however by the looks of the above posts your dermis isn't allowing anything thru.
They are good for a laugh though. And for that I thank you.
Nick1994
$100 site donor 2024
Originally Posted By: Clevy
Originally Posted By: Merkava_4
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Merkava
One would think that with the years you've spent here osmosis would have occurred and you'd have learned at least something however by the looks of the above posts your dermis isn't allowing anything thru.
They are good for a laugh though. And for that I thank you.
I agree. I've seen many posts from Merkava that have made me laugh my butt off at how odd his responses are.
Originally Posted By: Merkava_4
Originally Posted By: Quattro Pete
Originally Posted By: Merkava_4
10W-40 is basically a 30 weight oil.
What?
Yes, a 10W-40 averages out to a 30 weight in between full cold and full hot. It spends most of its time in the 30 weight range. Just like 10W-30 is basically a 20 weight and 20W-50 is basically a 40 weight.
Merkava
One would think that with the years you've spent here osmosis would have occurred and you'd have learned at least something however by the looks of the above posts your dermis isn't allowing anything thru.
They are good for a laugh though. And for that I thank you.
I agree. I've seen many posts from Merkava that have made me laugh my butt off at how odd his responses are.
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