| [GMCnet] What Oil Is Being Used [message #321809] |
Tue, 08 August 2017 16:00  |
Arthur Mansfield
Messages: 290
Registered: April 2010
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I have always used 20/50 oil in my GMC. Cold the old pressure reads just under 50 psi. Warm it reads a little over 35 on hot days. If the out side temperature is not hot the oil pressure gets close to 40 psi. I have been afraid to go to lower viscosity oil. Today I had to go to three stores to find 20/50 oil. I was thinking of going to synthetic oil 15/40 in the future.
I add Liquid Moly to the oil. I have used the Moly since the late 50’s.
Art
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| Re: [GMCnet] What Oil Is Being Used [message #321829 is a reply to message #321809] |
Wed, 09 August 2017 06:44  |
DetroitDan
Messages: 51
Registered: March 2017
Location: Taylor, MI
Karma: 0
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Mobil 1 10W-30
Drops the pressure a bit, but the volume is great for cooling bearings, etc.
Dan Wallace
Detroit Metro
1974 Canyon Lands 260
Headers, 3.55, 16"
Floor plan 26-9
Honda 6010
Harrison 4-bag
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| Re: [GMCnet] What Oil Is Being Used [message #321833 is a reply to message #321809] |
Wed, 09 August 2017 08:40 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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I'm using Valvoline VR-1 20W50. I was going to switch to Rotella-T 15W40, but O'Reilly's put the Valvoline on sale so I stocked up. Plus, I read a report that said the Valvoline had better friction fighting properties than the Rotella.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] What Oil Is Being Used [message #321848 is a reply to message #321809] |
Wed, 09 August 2017 10:09 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I've said this before but racing oils are the last thing I would use in a GMC MH
1) High in anti foam agents not needed in mid RPM range engines. We don't run 7000 RPM
2) Low in detergent. Racing oils are made to be raced and drained to remove contamination.
3) Low in ph stabilizers. These are needed in MH with long sitting and drain intervals. Again racing oils are meant to race then drain and dispose so not needed as it won't become acidic when removed and replaced
4) Low in additives to keep deposits in suspension. Again race/drain so not needed as it won't redeposit.
5) I don't go over 40 weight. Viscosity is the resistance to flow, and flow is what cools bearings. Also higher viscosity has poorer slinging and splash ability for cam, lifters and cyl walls and rings as well as flow to upper valvetrain.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] What Oil Is Being Used [message #321854 is a reply to message #321809] |
Wed, 09 August 2017 12:02 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Go back a week or two and look for a post by Fred Hudspeth on this topic.
He included a link to a blog that is chock full of tedious language, but
that describes actual friction protection at failure (of the oil). Based on
that, viscosity didn't have any real effect on the friction pressure the
oil would withstand, but oil is the primary coolant and needs to circulate.
Also, thinner oil drains back faster.
On my old engine, I used Mobil One High Mileage 15W50, and it made the
pressure gauge happy. But was it the best for the engine? The best oils in
that test were the latest 5W30 and 10W30's, and though they all overlapped
considerably, the best synthetics were better than the best dino oils. I'll
be switching to Mobil One 10W30 with my new engine starting with the next
change
Rick "recalling Dick P. saying that NSCAR runs at 8000 RPM all day at 30
psi, but oil pressure is NOT a problem with my new engine" Denney
On Tue, Aug 8, 2017 at 4:01 PM 1104agm wrote:
> I have always used 20/50 oil in my GMC. Cold the old pressure reads just
> under 50 psi. Warm it reads a little over 35 on hot days. If the out side
> temperature is not hot the oil pressure gets close to 40 psi. I have been
> afraid to go to lower viscosity oil. Today I had to go to three stores to
> find 20/50 oil. I was thinking of going to synthetic oil 15/40 in the
> future.
>
> I add Liquid Moly to the oil. I have used the Moly since the late 50’s.
>
> Art
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
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| Re: [GMCnet] What Oil Is Being Used [message #321856 is a reply to message #321854] |
Wed, 09 August 2017 12:45 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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New engines are a different animal than 40 year old cast iron monsters
designed in the 50's or 40's for use into the 60's or 70's. Dino oils were
all that was available, and your choice was detergent or non detergent, and
multiviscosity wasn't even a word back then. There was 20 wt. or 30 wt, and
10 wt for extreme cold weather. Engines lasted 80,000 to 100,000 miles.
Tuneups every 10,000 miles for engines equipped with points type
distributors.
Now? Overhead cams with roller cam followers, fuel injection, very tight
operating clearances, different metallurgy, synthetic oils, the game has
changed so much, it has all turned into guess work. Even the poorest oils
today are superior to the best oils of yesteryear. Use you favorite brand
in the correct viscosity for your area of the country and you should be
fine. Even the best oil won't make you any richer, or better looking or
more popular amongst the crowd you run with. Change it often enough to keep
contaminates from collecting in your pan, and the filter along with it.
That's what I think, your opinion WILL vary.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Aug 9, 2017 10:03 AM, "Richard Denney" wrote:
> Go back a week or two and look for a post by Fred Hudspeth on this topic.
> He included a link to a blog that is chock full of tedious language, but
> that describes actual friction protection at failure (of the oil). Based on
> that, viscosity didn't have any real effect on the friction pressure the
> oil would withstand, but oil is the primary coolant and needs to circulate.
> Also, thinner oil drains back faster.
>
> On my old engine, I used Mobil One High Mileage 15W50, and it made the
> pressure gauge happy. But was it the best for the engine? The best oils in
> that test were the latest 5W30 and 10W30's, and though they all overlapped
> considerably, the best synthetics were better than the best dino oils. I'll
> be switching to Mobil One 10W30 with my new engine starting with the next
> change
>
> Rick "recalling Dick P. saying that NSCAR runs at 8000 RPM all day at 30
> psi, but oil pressure is NOT a problem with my new engine" Denney
>
> On Tue, Aug 8, 2017 at 4:01 PM 1104agm wrote:
>
>> I have always used 20/50 oil in my GMC. Cold the old pressure reads just
>> under 50 psi. Warm it reads a little over 35 on hot days. If the out
> side
>> temperature is not hot the oil pressure gets close to 40 psi. I have
> been
>> afraid to go to lower viscosity oil. Today I had to go to three stores
> to
>> find 20/50 oil. I was thinking of going to synthetic oil 15/40 in the
>> future.
>>
>> I add Liquid Moly to the oil. I have used the Moly since the late 50’s.
>>
>> Art
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Rick Denney
> 73 x-Glacier 230 "Jaws"
> Off-list email to rick at rickdenney dot com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
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| Re: [GMCnet] What Oil Is Being Used [message #321859 is a reply to message #321857] |
Wed, 09 August 2017 14:22 |
Arthur Mansfield
Messages: 290
Registered: April 2010
Karma: 0
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Senior Member |
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Thanks everybody. I found the Castrol 20/50. Most of the local stores do not carry Castrol 20/50. Next time I will switch to 14/40 synthetic oil and see what the pressure drops to.
I add liquid Moly to the oil. It is a very good dry lube and I use it to protect the lifters along with the rest of the motor. It is more expensive but has worked for me if I wanted long life of a motor. My engine has only 25k miles since I rebuilt it. My motor needs to have the rings changed but I am to old to do a rebuild unless I have no choice.
Art
> On Aug 9, 2017, at 1:01 PM, Ken Burton wrote:
>
> Rotella 15W40
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
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