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

[TallPaul]

Originally Posted By: mechtech2

My pure speculation is that 20-40 was a more natural viscosity, and therefore subject to less breakdown.
Well I wonder how many conventional straight 40 weight oils would pass the 20w criteria and thus could be labeled 20w40 yet be straight weight.

 

[CATERHAM]

I'd say none. You may get some variation in the VI of GP I and GP II oils but not enough to span two viscosity grades without a healthy does of VII.

 

[TallPaul]

Originally Posted By: CATERHAM
I'd say none. You may get some variation in the VI of GP I and GP II oils but not enough to span two viscosity grades without a healthy does of VII.
I don't know about that, since the front number (W number) is classified very differently than the back number, it may be possible. API Chart for Reference

 

[exranger06]

My uncle just bought a brand new power washer. The owner's manual says to use 20w-40 for the pump.

I emailed the company and they said to just use 30 wt non-detergent instead.

 

[H2GURU]

That was a common formula used in racing in the early 70s, and I used it during the summer in a Beetle and it worked well.

 

[lexus114]

Originally Posted By: exranger06
My uncle just bought a brand new power washer. The owner's manual says to use 20w-40 for the pump.

I emailed the company and they said to just use 30 wt non-detergent instead.

I use Briggs & Straton Synthetic pump oil in my Faip one season wonder.And it going on three seasons now.

 

[beanoil]

Originally Posted By: CATERHAM
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.

20w40 was Yamaha's recommendation for oil for many years. I had a mid eighties Seca 750 that the manual specified 20w40 in. At that time, I was only able to find it at Yamaha dealers. The Seca survived quite well on a steady diet of Castrol 20w50. All Yamaha's new stuff is 10w40.

 

[MERWIN]

Recalling from the cob-webby portion or my brain:

Valvoline had a "turbo" formulation 20W-40 that I used in my 1984 Colt Turbo. Rave reviews from Consumer Reports (yeah, yeah, I know) at the time because it supposedly didn't cook down like the 10W-30s of the day and held up well in their shear test and ball bearing wear test. One day, it just dissappeared from the shelves.

 

[Shannow]

Working in a Shell (Oz) servo in 1987, their two oils were Super SF 20W-40, and XMO 15W-30.

If I knew then what I know now, I would have stockpiled the XMO instead of canning it like everyone else...

Then they introduced "XMO-Hi" which was the first time I saw XHVI "giving synthetic performance from a mineral basestock" it was a 40 (5W IIRC)