Need Viscosity recommendation in t his situation:

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Hi All!
Want a viscosity recommendation for this particular vehicle/situation:
1995 GMC 2500 with 454/4L80E; 200K mi, runs like new.
My daily commute is 7 miles, noticed last oil change and the most recent (15-40 Delo LE) (this is a flat tappet engine after all!)
Observations:
1. Oil pressure at start up goes to 65psi. Doesn't matter if in gear at 800rpm or neutral at 1200.
A. Is this at the bypass pressure, allowing oil to bypass the filter? This condition remains constant for 4-6 miles, at which time idle oil pressure drops to 40psi in gear.
2. After approximately 7 miles (in 90 degree plus heat), idle oil pressure drops to a steady 25psi at 700rpm in gear. Oil pressure above 1400rpm stabilizes at 60psi. These remain constant even after a highway run of 20-30 miles at 60mph, so I conclude the oil temp has stabilized. This vehicle was ordered with an engine oil cooler from the factory, max towing pkg. Towed 1500 lbs MORE than the diesel in 1995! 14 bolt rear, 4.10 gears, etc.
3. Given that 90% of my driving is to and from work, if 65psi is where the bypass opens negating filtering, a goodly portion of my daily drive is with the oil "unfiltered".
4. Would it be reasonable to change to a 0W-30 or 0W-40, given that the 40 is good after warming but the cold 15W seems to be too viscous at start up to NOT bypass the filter?

Opinions appreciated! All considered!

Kyle
 
The bypassed oil returns directly to the pan. None of it is used for lubrication. This bypass determines the oil pressure you see.

All oil used for lubrication has to pass thru the filter. There is another bypass in the filter, so it is possible for oil to be unfiltered if that bypass opens, using a big filter will minimize that. Using 5w40 rotella will pretty well ensure no bypass happens

Rod
 
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Those numbers are similar to the LS4 454 in the 73 vette I owned I built the motor and raised it to ~80 but at warm idle was ~25-30. The oil pump has a bypass to set the maximum working pressure to the engine. The filter bypass is only the pressure drop across the filter media

The 65psi you see is the set pressure of that bypass with cold thick oil. After warm up the 25psi represents the warm thin oil that can leakdown from all bearing journals more easily. Getting back to 60psi @ 1400 sounds great for that beast motor. :)

If you try lighter oils keep an eye on the warm idling pressure 25psi is low enough dont want it to go lower. I would just keep using that 15w-40 delo seemed to work so far. ...Dont the anti wear add packs reduce a lot with 0w -5w "Energy conserving" oils? the flat tappets appreciate having it.
 
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Kawiguy454: I now, right? I wonder if it was rebuilt at some point or is a later crate engine. I'll check the casting # at some point. When I bought it the mileage was 196K and I did the normal tune up, it has the small cap HEI system. Center contact was disintegrated and the plugs/wires were not anywhere near fresh. The oil pressure and super smooth running, along with rock steady 20" vacuum at no load idle seem to indicate very little wear. Can truly lay down a good stripe with single side 14 bolt with 4.10's! Shifts at 4000, feels like a shift kit. No leakage anywhere, doesn't burn any either.
 
You are confusing oil filter bypass with oil pump relief pressure.
The oil pump may have some of the excess oil at higher cold pressure routed back to the sump while the oil filter isn't in bypass. The wall you hit in cold oil pressure doesn't mean that the oil filter is in bypass. It probably isn't.
You probably do have too cold oil for your daily commute.
What if you blank off the oil cooler with some sort of cover for daily use and then remove it for longer drives?
Unless you ever work the truck hard, why not just bypass the oil cooler entirely and permanently? It could always be brought back into the circuit if the truck is ever to be used for hard towing.
Your choice of oil grade is fine for the lowest temperatures you'll ever see in Florida.
If you're concerned, another six bucks or so a gallon will get you Delo 5W-40.
 
You can try a lighter oil and see how the oil consumption is. I think you are wasting effort thinking this out though. What exactly are you trying to gain? Oil 101?
 
The consensus I've found on the 454 is, "Just as long as it's got oil in it." If it's a flat-tappet engine it's very late - is it Vortec injection or throttle body? I thought they went to roller cams at the same time Vortec features were introduced for both the 350 and 454.

I have an '85 1-ton with 454/TH400/4.10's (carbureted) and my BIL's dad has a '98 K2500 Suburban with Vortec 454 - he's run Schaeffer's 7000 10w30 in it for some time and it has somewhere over 270K on it with good vitals. Mine only has 123K - I ran Schaeffer's 7000 15w40 in it for quite a while but switched to 10/30 early this year and am very pleased. 15/40 was overkill in that engine compared to a quality 10/30 like Schaeffer's. Your hot idle oil pressure is something to keep an eye on - I wouldn't want it to drop much further. I'd try stepping down to a 10/30 (preferably syn blend - I saw my '85's hot idle oil pressure drop 10 PSI after less than 3000 mi. on VWB 10/30 and never put conventional in it again), see how your oil pressure behaves, and go from there.
 
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Alex_V: This is a 1995, last year of the flat tappet/Throttle Body before the Vortec. This one off year used a higher fuel pressure than previous years. After working on carbs for 40 years, this is the first TB I've owned or worked on. Airflow restricted to about 650 CFM but surely don't need even that most of the time. This engine rarely sees 3000 rpm. Oil consumption is -0- with a 5K OCI.

CT8: AH, thanks for the clarification. I thought that when the pressure reached a certain level, i.e. cold start, oil bypassed the filter to avoid burst danger (even though the specs on good filters show a minimum of 300psi to rupture). That being the case, I'll just run what I have until next OC, and maybe go a little lighter as an experiment. Since it holds so much, if I need to modify it after that, I can drain off some for the Ford. 2000 exploder with the OHC/chain casette rattle. Sometimes. Occasionally. LOL. Inveterate incorrigible tinkerer.
 
Originally Posted By: 08versa
Alex_V: This is a 1995, last year of the flat tappet/Throttle Body before the Vortec. This one off year used a higher fuel pressure than previous years. After working on carbs for 40 years, this is the first TB I've owned or worked on. Airflow restricted to about 650 CFM but surely don't need even that most of the time. This engine rarely sees 3000 rpm. Oil consumption is -0- with a 5K OCI.


Ah! I was off by a year. Very nice. Mine leaks from so many different places (more every day, it seems) I can't begin to gauge consumption. Schaeffer's keeps it clean, that's for sure! It's getting a full re-seal as soon as I can afford it.
 
Since your trips are short and you never get the engine up to temp , i'd use a lighter oil.( i doubt you are getting the oil to operating temp and viscosity in 7 miles so its always a heavy oil). You want zinc for the flat tappets so how about rotella t5 10w 30? If you want to spend more, you could use amsoil HDD ( heavy duty diesel) which is in a 5w 30.
 
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I'd use Shell Rotella T5 Syn blend 10W-30 , maybe even Valvoline VR1 10W-30 but you'd have to change it at around 5000 miles with VR1.
Mobil 1 0W-40 Or Shell Rotella 5W-40 would be ok too
 
Originally Posted By: 08versa
2. After approximately 7 miles (in 90 degree plus heat), idle oil pressure drops to a steady 25psi at 700rpm in gear. Oil pressure above 1400rpm stabilizes at 60psi.


My Buick never drops below 38 psi at idle with the oil fully hot. Off idle motoring down the road it goes up to 67 psi and that's with 10W-30. I think you need a 40 weight. Most GM truck engines run better with a 40 weight anyway.
 
It's the Delo LE 15W-40 now. Ahhh... experimentation! Not drilling/tapping idle bleeds on a Holley, but should satisfy my need to tinkerate!
 
Originally Posted By: Merkava_4
Originally Posted By: 08versa
2. After approximately 7 miles (in 90 degree plus heat), idle oil pressure drops to a steady 25psi at 700rpm in gear. Oil pressure above 1400rpm stabilizes at 60psi.


My Buick never drops below 38 psi at idle with the oil fully hot. Off idle motoring down the road it goes up to 67 psi and that's with 10W-30. I think you need a 40 weight. Most GM truck engines run better with a 40 weight anyway.


Buick? What Buick? Been a fan since forever, had a 64 skylark 225 V6 auto; 64 skylark 225 V6 three on the tree; 68 wagon with 350 4 barrel and powerslide; 70 coupe, my personal favorite, 315hp 350 GS engine in an unmarked, column automatic bench seat brown metallic love machine; 71 GS455 rebuilt in mama's tarazo (concrete) floored living room, painted it Cadillac blue firemist with flat black skunk stripes. Wished I'd known about Kenne-Bell. [censored] not having internet back then.
 
Originally Posted By: 08versa
Buick? What Buick?


2000 Buick LeSabre with the infamous 3800 Series II V6 . It puts out 205 horses with its roller lifters and roller rockers. It's got 65 psi at cold start and usually hovers around 40 psi when the oil's hot.
 
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