Home » Public Forums » GMCnet » Oil Pressure Poll
| Oil Pressure Poll [message #366554] |
Tue, 07 September 2021 19:54  |
Greg C.
Messages: 224
Registered: October 2019
Location: Knoxville, TN
Karma: 0
|
Senior Member |
|
|
So today I got my Autometer oil pressure gauge hooked up. I also have the factory gauge, with a NOS Made In USA Echlin OP6636 sender. I'm currently running 10-30 synthetic oil. Today's temperature was about 82. I started up the engine so I could run my new Viair compressor and evaluate its performance.
On start up, my stock gauge showed a little bit above halfway, and the Autometer gauge showed about (no exact corresponding lines) 30-32 PSI at about 900 RPM. After running a bit and kicking off the fast idle, the Autometer showed 25 PSI @ 650 RPM and 180 degrees water temp.
I went back and messed around with the compressor and checked for leaks for a few minutes. Going back into the cockpit showed 195-200 degrees and about 12-13 PSI of oil pressure at 650 RPM. Revving up to 1500 RPM netted about 30 PSI.
Those of you who have aftermarket gauges, how does this compare to yours?
Greg Crawford
KM4ZCR
Knoxville, TN
"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
|
|
|
|
| Re: Oil Pressure Poll [message #366555 is a reply to message #366554] |
Tue, 07 September 2021 19:58  |
Greg C.
Messages: 224
Registered: October 2019
Location: Knoxville, TN
Karma: 0
|
Senior Member |
|
|
Another interesting fact. I have never heard my (new) clutch fan kick in other than at the first crank of the day.
Today, while watching the gauges at idle, the temp climbed to 205 degrees.
I have a new core in the stock radiator, a heavy duty fan clutch, and a Robert Shaw 195 degree thermostat, tested on the stove before install.
While I watched the gauge, the fan kicked in at 205 degrees indicated, and ran until the temp gauge dropped to 180 degrees. I was impressed. And relieved that the fan seems to be working correctly.
Greg Crawford
KM4ZCR
Knoxville, TN
"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
|
|
|
|
| [GMCnet] Re: Oil Pressure Poll [message #366556 is a reply to message #366554] |
Tue, 07 September 2021 19:58 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
|
Greg,
How many miles are on the engine.
On Tue, Sep 7, 2021 at 5:54 PM Greg Crawford
wrote:
> So today I got my Autometer oil pressure gauge hooked up. I also have the
> factory gauge, with a NOS Made In USA Echlin OP6636 sender. I'm currently
> running 10-30 synthetic oil. Today's temperature was about 82. I started
> up the engine so I could run my new Viair compressor and evaluate its
> performance.
>
> On start up, my stock gauge showed a little bit above halfway, and the
> Autometer gauge showed about (no exact corresponding lines) 30-32 PSI at
> about
> 900 RPM. After running a bit and kicking off the fast idle, the Autometer
> showed 25 PSI @ 650 RPM and 180 degrees water temp.
>
> I went back and messed around with the compressor and checked for leaks
> for a few minutes. Going back into the cockpit showed 195-200 degrees and
> about 12-13 PSI of oil pressure at 650 RPM. Revving up to 1500 RPM netted
> about 30 PSI.
>
> Those of you who have aftermarket gauges, how does this compare to yours?
> --
> Greg Crawford
> KM4ZCR
> Knoxville, TN
>
> "Ruby Sue"
> 1977 Royale
> Rear Bath
> 403 Engine
> American Eagle Wheels
> Early Version Alex Sirum Quad bags
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
|
|
|
|
| Re: [GMCnet] Re: Oil Pressure Poll [message #366559 is a reply to message #366556] |
Tue, 07 September 2021 20:15 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
The machine work on my engine was done at Larry's Engine and Marine here in Tucson. Larry has extensive experience with Olds 455 engines, having built literally hundreds of them over the years for jet boat and hot rod applications. He understood the motorhome application and provided machine shop and parts services accordingly. The bearing clearances were set up specifically for 20W50 oil due mostly to the giant size of the main journals on the crankshaft of a 455. This was Larry's recommendation. I had already been running 20W50 oil, at Jim Bounds' suggestion before the rebuild.
Last year, about this time, we embarked on a 3500 mile trip to The Grand Tetons, Yellowstone, Devil's Tower, Rapid City, and back through several Wyoming and Utah national parks and monuments. Right before that trip, I had decided to experiment with 15W40 Rotella oil instead of the Valvoline 20W50 I had been using. I noticed my oil pressure running lower than usual as a result and stressed about it for most of the trip. I changed back to the 20W50 and the oil pressure (on the stock gauge)returned to what it had been before. I won't run anything in it but 20W50 again.
Maybe you need to run a heavier oil in it, at least 15W40, if not 20W50.
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
|
|
|
|
| Re: Oil Pressure Poll [message #366561 is a reply to message #366554] |
Tue, 07 September 2021 20:34 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
Heavy oil makes gauge read higher because there is less flow. Flow is what cools bearings, pistons and valvetrain. As long as you are over 10 PSI per 1000 rpm you should be ok. Above 60 PSI the bypass starts to open anyway. The vented oil goes back to pump inlet instead of to parts where it can lube and clean and cool them. Paraphrasing Dick Patterson’s Olds oiling presentation.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
| Re: Oil Pressure Poll [message #366565 is a reply to message #366554] |
Tue, 07 September 2021 22:26 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
|
Senior Member |
|
|
The one thing I have learned is that with today’s oils, thicker is not better. IMO, it is best to use as thin of an oil as possible, that gives you acceptable hot oil pressure. The thinner it is, the more oil you have going to bearings, reducing wear. The thinner it is the more oil is carrying heat away from moving parts. The thinner it is at cold temps, the quicker oil gets to the bearing surfaces reducing wear. The thinner it is at cold temps, the more oil you have actually going to those cold surfaces quicker, reducing wear. I use the 0W40 mainly because the “0” flows for my Wisconsin cold winter starts, (sometimes we leave for the south in -15*) while giving me the “40” for acceptable oil pressure on hot running. On cold starts, I have oil pressure immediately with the "0", and 45-48lbs hot running down the road, and 30lbs and a hot idle. I think it is Matt C. that once said, the only down side is the “0” also has a run-off factor when sitting for long periods, meaning because of the low viscosity, it runs off easier than the 5w to 15w weights when sitting for long periods. If my coach has been sitting for more than a couple of months, I get by that by pulling the ignition wire and turning the engine over until I see the needle move on the oil pressure gauge….then hook up the wire and start. A minor inconvenience but IMO worth the effort.
I think it was Matt that said that it is hard to find a "bad" oil out there, so to my way of thinking, if you have engineering and scientific testing that shows certain oils are better than others in reducing wear, why not go with it.
Oils have improved immensely over the years. Todays knowledge of chemistry and engineering have created oil blends that give us oils that far exceed the wear characteristics of yesterday’s blends. Todays blends have chemical replacement elements that duplicate the elements of ZDDP, so there may be only traces or no ZDDP in the oil, yet have extremely high wear characteristics. These oils have been formulated to assist todays engines in meeting EPA standards. Since most of us are not experts in the wear characteristics of oil, we act on what we know from our past knowledge and experiences. The past is behind us and while relevant, we need to look at present engineering going into the future. I’ve done as much as my pea brain will tolerate in researching the best oil for my Cad 500. So far the best I have found is a blog by a guy that calls himself 540Rat. He has taken the time using engineering techniques to test over 240 different oil blends, and ranked them by their ability to resist wear.
https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/
This is a tough read filled with testing, engineering data, a lot of self praise/bluster, and a lot of information that we don’t need, but is the best I have found to help me in my decisions relative to the oils that I am using in my vehicles. While it would be best to read most of the beginning info, for the meat of the blog, grab the scroll button and scroll about 1/10 of the way down to “WEAR PROTECTION RANKING LIST”. This lists oil in their ability to resist wear by measuring in psi their ability to keep metals from making contact. It should be noted that while he has tested an number of them ranked very high on this list that have an aftermarket oil additive, he does NOT endorse the use of oil additives claiming that you really don’t know what you are doing to the carefully engineered chemical blend when you pour in these additives. So he claims it is best to choose an oil that ranks high on the list straight out of the bottle.
The Wear Protection reference categories are:
* Over 150,000 psi = SPECTACULAR wear protection
* 135,000 psi to 150,000 psi = AMAZING wear protection
* 120,000 psi to 135,000 psi = FANTASTIC wear protection
* 105,000 to 120,000 psi = INCREDIBLE wear protection
* 90,000 to 105,000 psi = OUTSTANDING wear protection
* 75,000 to 90,000 psi = GOOD wear protection
* 60,000 to 75,000 psi = MODERATE wear protection
* 50,000 to 60,000 psi = UNDESIRABLE LOW wear protection
* Below 50,000 psi = CAUTION – EXTREMELY LOW wear protection
The HIGHER the psi value, the BETTER the Wear Protection.
I personally use # 1 5W30 Quaker State “Full Synthetic” = 152,674 psi. in my automobiles and #15. 0W40 Mobil 1 “FS” European Car Formula, synthetic = 127,221 psi, in my motorhome.
If you want to see where the oil you have been using ranks, do a command F or Control F, type in the brand of oil, and hit CR to advance through the article until you find it. Some of the oils that have been the staple of the GMC community for years are surprisingly low on the wear protection list.
Sooooo….judge for yourself. Choose wisely by making informed choices.
JMHO
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
[Updated on: Wed, 08 September 2021 06:34] Report message to a moderator |
|
|
|
| Re: Oil Pressure Poll [message #366572 is a reply to message #366554] |
Wed, 08 September 2021 06:20 |
Greg C.
Messages: 224
Registered: October 2019
Location: Knoxville, TN
Karma: 0
|
Senior Member |
|
|
Jim, the engine has 67,000 miles.
Greg Crawford
KM4ZCR
Knoxville, TN
"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
|
|
|
|
| Re: Oil Pressure Poll [message #366577 is a reply to message #366554] |
Wed, 08 September 2021 08:45 |
Greg C.
Messages: 224
Registered: October 2019
Location: Knoxville, TN
Karma: 0
|
Senior Member |
|
|
Larry, I have read the 540 Rat blog a few times. I'm running Quaker State Ultimate Durability after reading his blog. Maybe I need to change to 10W40.
Thank you for taking the time to respond with all that information.
Greg Crawford
KM4ZCR
Knoxville, TN
"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
|
|
|
|
| [GMCnet] Re: Oil Pressure Poll [message #366578 is a reply to message #366565] |
Wed, 08 September 2021 08:55 |
|
|
Thanks very much for this, Larry. Very interesting and changed my thinking
on oil pressure.
I'll try it. I'm due an oil change on two other of my high
mileage vehicles AND the GMC.
:-)
bdub
On Tue, Sep 7, 2021 at 10:26 PM Larry wrote:
> The one thing I have learned is that with today’s oils, thicker is not
> better. IMO, it is best to use as thin of an oil as possible, that gives
> you acceptable hot oil pressure.
> ... snip ...
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
bdub
bdub.net
|
|
|
|
| [GMCnet] Re: Oil Pressure Poll [message #366581 is a reply to message #366578] |
Wed, 08 September 2021 11:44 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
|
My experience is that the pressure can decrease after the engine reaches
over 50.000 miles and also how long the engine sat around.
On Wed, Sep 8, 2021 at 6:55 AM Billy Massey wrote:
> Thanks very much for this, Larry. Very interesting and changed my thinking
> on oil pressure.
>
> I'll try it. I'm due an oil change on two other of my high
> mileage vehicles AND the GMC.
>
> :-)
> bdub
>
>
> On Tue, Sep 7, 2021 at 10:26 PM Larry wrote:
>
>> The one thing I have learned is that with today’s oils, thicker is not
>> better. IMO, it is best to use as thin of an oil as possible, that gives
>> you acceptable hot oil pressure.
>> ... snip ...
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
|
|
|
|
| Re: [GMCnet] Re: Oil Pressure Poll [message #366602 is a reply to message #366581] |
Wed, 08 September 2021 17:28 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
I knew I'd get flamed for my choice of 20W50 oil, but that is the weight my particular engine was machined and clearanced for. If you feel confident that your main and rod bearings are set up tight enough (like most modern engines are) then maybe a light oil is a good choice for you. If not, you might want to err on the side of caution and use a somewhat heavier oil, especially in a higher mileage engine or one in unknown condition. My personal opinion.
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
|
|
|
|
| Re: [GMCnet] Re: Oil Pressure Poll [message #366614 is a reply to message #366578] |
Wed, 08 September 2021 21:05 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
|
Senior Member |
|
|
Billy Massey wrote on Wed, 08 September 2021 08:55Thanks very much for this, Larry. Very interesting and changed my thinking
on oil pressure.
I'll try it. I'm due an oil change on two other of my high
mileage vehicles AND the GMC.
bdub
On Tue, Sep 7, 2021 at 10:26 PM Larry wrote:
> The one thing I have learned is that with today’s oils, thicker is not
> better. IMO, it is best to use as thin of an oil as possible, that gives
> you acceptable hot oil pressure.
> ... snip ...
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
Keep in mind that if you go from a... say...15w40 to a 5w30 that your oil pressure will likely drop. That is not a bad thing as long as pressure is at the 10 lbs per 1000 rpm. If you are not comfortable with that kind of drop go for the 0w40 or 5w40 as long as it is high on the wear protection list. JWID. Thick oil does not give you protection from wear. JWIT
Larry
78 Royale w/500 Caddy
Menomonie, WI.
|
|
|
|
| Re: Oil Pressure Poll [message #366625 is a reply to message #366554] |
Thu, 09 September 2021 08:49 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
I have run only Shell T6 (Blue jug) full synthetic since my Cinnabar engine was installed. This is a 5W-40 oil that was branded as for both Diesel/Gasoline engines. Recently Shell marketed Rotella Gas Truck full synthetic (Red Jug) oil and removed the gasoline icon from T6 . Did they make it not for gasoline or just want to sell the new Gas Truck Rotella syn? Can only guess. I asked Dick Patterson about my oil choice and he highly praised the T6. Fall camping we have woken to teens F and have effortless starts, whereas earlier in trip we were in the 90s. This wide range as Larry suggests is good at outsmarting Mother Nature. Now the wider the viscosity spread, the more viscosity modifiers they have to use to accomplish this. That’s not desirable as the viscosity modifiers can break down before other oil components. Example: My 80s Buick manual recommends 10W-30, but 5W-30 when temps expected below zero. Why not just run 5W-30 year round as both are 30 hot? Because of the viscosity modifiers noted above, less spread is better in summer. However— with synthetics the wide spreads are rated without excessive viscosity modifiers being necessary so a win win. Since I only carry one oil type on board, I run only T6 in the Onan as well. Some claim of ‘glassy deposits’ in air cooled engines from synthetics, but my Onan has never let me down so that’s my benchmark.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
Goto Forum:
Current Time: Thu Jun 20 07:11:10 CDT 2024
Total time taken to generate the page: 0.01864 seconds
|
GMCforum
Search
Help
Register
Login
Home
