'20W-40' oil grade - anyone know the history?

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addyguy

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If you look in older owners manuals/oil guides (ie, 1970's), you often see recommendations for '20W-40' oil. I know I've also read here that some members used to use this grade of oil.

Does anyone know what the 'history' of this grade is? It seems it was only around in the 1970's - was it a brief 'flash in the pan' grade? I've also read that it was the predecessor to the modern 15W-40 grade, so was it just a HDEO grade? I know I've seen it in regular gas engine manuals, so was it both a PCMO grade and a HDEO grade?

Any info would be great - just curious!
 
Wow... the only place I see this anymore is for marine engines. I'd use it in place of 15w40, why not? Almost guaranteed to be VII-free
 
Used some Kendall Superb All Seasons 20w40 long long time ago. Can't remember it being rated for diesels. Kendall made a product named DSL for automotive/light truck diesels back then.
 
I used the Quaker State Super Blend in 20W-40 in my SAAB 900 in the mid-late 1980s. This was a standard PCMO formula. A google search returned a MSDS for this oil dated July 1990.

This was a great oil and an answer to the VII issues of the era. I used The Super Blend 20W-40 in the summer and the Super Blend 10W-30 in the winter.

Ed
 
This is just from memory and isn't what you're seeking for "knowing" . It was primarily a fleet oil. When in autoskewl, the brand the school has on hand was Arcofleet 20w-40. It would tend to make sense that a future evolution would be 15w-40.

While it was available for NG applications (low ash) this appears to have evolved to 15w-40... probably due to less tweaking required of better VI in basestocks.

Amsoil markets one SAE (20W)-40 Synthetic Natural Gas Engine Oil (ANG)
 
Don't know the history but for 10 years I used Pennzoil 20W-40 racing oil in my 68 Hemi RoadRunner. Johnny is familiar with this oil. When it became unavailable I switched to Kendall GT-1 racing oil in 20W-50. After it's recent rebuild it was broken in on a 10W-30 HDEO and now enjoys a crankcase of M-1 10W-30. Finally getting it out of the paint shop Sat. This guy is slow but good. He's had the car for 3 1/2 mo's. This is the longest I have been apart from this car in the 40 yrs I have owned her. Will post pics when I get her back.
 
The Firestone Stores in TN carried Kendall 20w40 as their standard bulk oil from at least '77 to '82. I had a company car in those days that had a National Service Contract with Firestone. I parked it outside at night. We had a couple real cold snaps in winter and that oil was like glue. I remember complaing to the Firestone Mgr and his reply was that was the only oil they were carrying. Then they switched over to Kendall 10w40.
 
I made my own 20w40 once by mixing equal parts of 20w50 and straight 20w. It was summer, so of course I didn't have any startup problems.
 
Frequently see around here, as well as 25W-50. One way to reduce the shear problem of lousy base oils. Usually only seen in the cheap brands.
 
I'm going to date myself, but it was the spec' oil for many British motorcycles such as Triumph and BSA in the late 60's early 70's. Castrol 20W-40 was very popular. An idiot friend of mine thought It would be "cooler/better" to run Castrol GP 40 wt instead in his new Triumph Bonneville and on a very cold day he promptly seized the engine.
My '69 Norton Commando still spec'd a straight 50 weight though.
 
We used chevron 20w-40 in our state patrol cars back in the 70's. The mopar vehicles back then called for at least this grade if used in police cars.
 
Interesting info, thanks!

Sounds like it was a VERY common grade used back in the 1970's and 1980's...
 
Like someone else said, Yamaha still makes and recommends it. I had a '85 Yamaha FJ1200 that went 60k miles on inconsistent oil changes with 15w-40. When I took it apart at 60k miles to replace 2nd gear, the bearings still had the original finish on them. They plastigauged within factory spec.
 
The most common grade was 10-40. 20-40 was not real common.
My pure speculation is that 20-40 was a more natural viscosity, and therefore subject to less breakdown.
 
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