This topic can go on till the cows come home as there is only a small
difference as to slight chang in viscosity.
Just use sun oil and worry about other more important things.
On Sat, Jun 13, 2020 at 5:41 PM James Hupy via Gmclist <
> Shafts and bushings are kept separated from each other by something known
> as "a fluid wedge" created by the shearing away of oils by the unequal
> speed of both surfaces. Viscosity has a bit to do with this, but I am not
> sure just how much. Experts have never, ever agreed on this. I used to run
> 10w-30 H.D. Valvoline Dino oil in my 403 in my Royale, and my low oil
> pressure at idle always bothered me. So I switched to 20w - 50 H.D.
> Valvoline Dino oil. Much higher now at 140,000 miles on the clock.
> Engines in current applications were manufactured with synthetics with
> low viscosity in mind. Their clearances are wayyy tightened up compared to
> our cast iron dinosaurs. They also rev a lot, lot higher. Over 2 1/2 times
> higher than our Oldsmobiles do.
> So, most of the writers for road and track and other similar
> publications tout synthetic oils, because the companies advertise heavily
> in their magazine. If you bite the hand that feeds you, you won't have a
> job very long. Synthetics do a bang up job in engines designed for them. No
> argument from me on that point.
> Like I have always said. Opinions Vary. I appreciate your viewpoint.
> Jim Hupy
> Salem, Oregon
>
> On Sat, Jun 13, 2020, 5:15 PM Larry via Gmclist
>
> > Here is an article entitled "Motor Oil Engineering Test Data". It is a
> > long read with lots of repetition. Tests were run on 239 different oils
> or
> > oils
> > with after market additives. Oils are ranked by their ability to resist
> > wear. An interesting read as most of the higher ranked oils are of
> > relatively
> > low viscosity. 5w30's, 0w20's etc. Here is a copy/paste of a section
> > written about viscosity.
> >
> > SECTION 2 – MOTOR OIL VISCOSITY SELECTION
> >
> > THE BENEFITS OF USING THINNER OIL:
> >
> > • Thinner oil flows quicker at cold start-up to begin lubricating
> critical
> > engine components much more quickly than thicker oil can. Most engine
> > wear takes place during cold start-up before oil flow can reach all the
> > components (the longer an engine has been sitting, the more of a concern
> > this
> > becomes), and during warm-up while the oil is still thicker and not
> > flowing as freely as it does during normal hot operating temperature. So,
> > quicker
> > flowing thinner oil will help reduce start-up and warm-up engine wear,
> > which is actually reducing wear overall.
> >
> > • The more free flowing thinner oil during cold start-up and warm-up, is
> > also much less likely to cause the oil filter bypass to open up, compared
> > to thicker oil. Of course if the bypass opened up, that would allow
> > unfiltered oil to be pumped through the engine. The colder the ambient
> > temperature, and the more rpm used when the engine is cold, the more
> > important this becomes.
> >
> > • Thinner oil also flows more freely when fully warmed-up to normal
> > operating temperatures. And oil FLOW is lubrication, but oil pressure is
> NOT
> > lubrication. Oil pressure is only a measurement of resistance to flow.
> > Running thicker oil just to up the oil pressure is the wrong thing to do,
> > because that only reduces oil flow/lubrication. Oil pressure in and of
> > itself, is NOT what we are after.
> >
> > • The more free flowing thinner oil will also drain back to the oil pan
> > quicker than thicker oil. So, thinner oil can help maintain a higher oil
> > level in the oil pan during operation, which keeps the oil pump pickup
> > from possibly sucking air during braking and cornering.
> >
> > •The old rule of thumb for desired oil pressure, that we should have at
> > least 10 psi for every 1,000 rpm, pertains to, and is highly recommended
> for
> > High Performance and Racing engines. Engine bearing clearances are
> > primarily what determines the oil viscosity required for any given
> engine.
> > (NOTE:
> > Viscosity does NOT determine an oil’s wear protection capability, like
> > many people think. Wear protection capability is determined by an oil’s
> > additive package, which contains the extreme pressure anti-wear
> > components. That is why 5W30 oils can perform so much better than thicker
> > oils in my
> > wear protection capability testing). But, whatever the bearing clearance,
> > for High Performance and Racing engines, it is best to run the thinnest
> oil
> > we can, that will still maintain at least the old rule of thumb oil
> > pressure, even if that means using a high volume oil pump to achieve
> that.
> > A high
> > volume oil pump/thinner oil combo is much preferred over running a
> > standard volume oil pump/thicker oil combo. Because oil “flow” is our
> goal
> > for
> > ideal oiling, NOT simply high oil pressure. So, one of the benefits of
> > running a high volume oil pump, is that it will allow us to enjoy all the
> > benefits of running thinner oil, while still maintaining desirable oil
> > pressure.
> >
> >
> >
> > I have been using two of the higher ranked oils on this list in my
> > personal vehicles including our GMC. I have been very happy with the
> > performance of
> > 0w40 Mobile 1 (ranked #7) used in my Cad 500 powered GMCMH. I am thinking
> > about going to (ranked #4) 5W30 Quaker State Ultimate Durability, dexos
> 1
> > – Gen 2, API SN “Plus”, synthetic (green bottle), because of it's higher
> > wear rating. Both of these oils are available at local Walmarts at very
> > reasonable pricing.
> >
> > So, the above is all Just My Humble Opinion backed by a few facts that I
> > found on the Web. Other opinions will vary.
> > --
> > Larry
> > 78 Royale w/500 Caddy
> > Menomonie, WI.
> >
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
