NGC - thicker oil or additives for low oil pressure

[brider]

Well, this MIGHT have Guzzi content if you're concerned about your Guzzi's low oil pressure, but my concern is with a high-mile GM-ish V8.

Does anyone have a positive opinion of oil additives to "help" a tired engine's oil pressure (at idle)? I've always poo-pooed them, but never HAD an engine tired enough to consider them.

The owner's manual allows 20W-50 down to 32 deg F, and 10W-(30,40,50) down to -10 or -20 deg F.  Running 10W-40 now.

My first thought would be to change to 20W-50 NOW, and hope to have the presence of mind to switch down to a 10W before the cold days of winter.

V8 has 204k miles on it now, and runs great with no oil burning. HOWEVER, just recently I discovered the oil light flickering on when hot, like after a long highway run and then screeching to a halt because of a typical CT highway backup. Light will flicker at a very low idle (another issue I decided to ignore since it's a FI, ECU-controlled  engine and no real way to adjust idle) until the traffic starts creeping, where the revs can bump up a bit.

I learned quickly to shift to N while stopped to let the revs bump up, which shuts the light off, but still....

This is a '93 Range Rover, engine is a Buick clone 4.2L. Waaaaaay too many irons in the fire now to rebuild or re-power, so my first effort will be to nurse it along and hope to not do damage while at low revs. One thing I WILL do (since it's easy and I already have one) is install a mechanical old-school guage to have a better idea of the pressure-profile.

Thanks in advance for any opinions (personal or otherwise).

[Moparnut72]

Put a gauge on it first thing. Oil pressure switches for idiot lights are known to fail. Low oil pressure at idle is not necessarily a bad thing. If you have at least 10lbs at idle don't worry about it as l long as it goes up at higher rpm. There is a rule of thumb of how much pressure you should have at each 1,000 rpm but I don't remember what it is.
kk

[Stretch]

"Oil pressure switches for idiot lights are known to fail."

This.

Not an expensive part, but can sometimes be a BEAR to get to!

                                                 -Stretch

[bmc5733946]

Some of the electrical connectors at oil pressure senders/switches are sealed to the sender/switch body. If the sender/switch leaks into the sealed cavity provided by the connector applying pressure to the back of the sender, it can activate the sender/switch essentially in reverse. Late model Chrysler built wiring systems are known for this some GMs as well. Remove the seal and the unit reads correctly but leaks, leave the seal and the light or indicator shows low oil pressure. YMMV

Brian

[John A]

I think changing to 20-50w is a good idea. Won’t hurt anything if it doesn’t help and it might do the trick until you can get the idle speed up a little

[krglorioso]

For many years Harley-Davidson dealers would have been happy to sell you Harley-Davidson brand motor oil in SAE 70 weight.  Maybe they still do.

Just sayin'

Ralph

[Old Jock]

General rule is 10psi per 1k RPM

First thing I'd do is put temporary or permanent gauges onto it for both oil pressure and temperature. That way you'd have some idea if you've got an issue or if it's a bad switch.

Oil temp is important as you need to determine if it's a high temp that's causing the low pressure as viscosity and temp isn't linear.

I've got a similar issue with an early HiCam Daytona RS lump, which hates town running and overheats, but that's mainly due to the mad cams installed in the non US RS engine and not installed in any of the other HiCams.

The oil light comes on at idle after low speed and traffic with pressure being as low as 5psi with a low idle. Moving from a 15/50 to 10/60 helped and upping the idle RPMs from 1100 to 1500. When below 1500 RPM the oil pump just isn't turning fast enough to generate enough pressure and oil temp is up at 120C (when that happens I stop and let it cool)

[LowRyter]

I think that's what STP was designed to do.   I know the mere suggestion could start a rage war.  For the record, I've never used the stuff.

[brider]

Thanks, all. I'll install that oil pressure guage I've had laying around and switch up to 20W-50. I wish I could manually bump up the idle speed but there is no standard procedure to do that. Just shifting to neutral bumps the revs up I'd guess 200 rpm, which is enough to shut the light off. Agreed, the light itself is a poor indication, but I still don't like it to be on.

One think I WILL say is that even at low idle or cold start-up, there is no lifter noise or engine rattling/knocking at all. I'll take that as a good sign.

Thanks again, nothing much more to say about this.

[MattP]

A higher viscosity oil will always raise the oil presher always. in your case probubly plenty being cheap we tend to be , Just changed oil? stp ready for a oil change heaver weight oil.

[Kev m]

Why not 10-50?

[Brand X]

Maybe replace the oil ring in the pick up tube.(might as well change the oil pump too)  Also, the line could be somewhat plugged going to the sender.  Common LS Problems f that is the GM you are talking about..

[MattP]

I had 5 of 215 v8s 1 61 buick spechel 3 spares and a mint tr8 convert.  Did a lot of reasurch on these and it was my understanding that these engines ran high volume rather than high presher oil systems . The peramaters i do not recall, and i mabewrong , how ever the tr8 did the same as yours. I sold it,not because of it how ever. It was to nice to sit out in the rain and snow. And if the person i got it from left the stock fuel injection on it i would have found a place to keep it.

[brider]

I had 5 of 215 v8s

I believe my Range Rover engine IS a descendent of this Buick engine. It's an OLD design. If it got to the point where I needed/wanted to drop the oil pan, that's when I'd park it and plan for a re-power, which I've known I'd have to do sooner or later.

10W-50 is a smart choice, thanks.

[pressureangle]

That particular engine is famously weak, but robust. As everyone has said, verify the pressure and sending unit. There aren't really many options if it needs mechanicals, and hot oil pressure changes little between grades. If it was mine, and you don't expect any sub-zero weather, put a straight-weight sae 50 in it and run it until it drops.

[MattP]

I do belive your oil pump is on your timing cover driven by the disturber ,the oil filter housing and pump i seam to rember are one and the same. I think you may be able to replace the pump with out even removing the timing cover. I mean you certinaly can remove the oil filter so I would hope there is enoigh room to pull the pump..butfrom what i do recall the instalation of hi output voluem and or presher will result in wiped out dist, gear. Stock pump. crawl under the bitch. It may take more time to read my pecking than to do the job. hope this helps

[pressureangle]

Everything I never thought to know about Buick/Rover v8's.

https://www.gomog.com/allmorgan/plus8oil.htm

[brider]

Everything I never thought to know about Buick/Rover v8's.

https://www.gomog.com/allmorgan/plus8oil.htm

Great reading and I THINK it applies to my engine, but what the heck is a "Plus 8"?

[Moparnut72]

Referring to a Morgan model???? Interesting article. I know that early small block Chevys were dependent on high volume as opposed to pressure. I once assembled a Studebaker V8 with the help of a friend who did a lot of this kind of thing. Clearances were all within Chevy specs. I had to do it all over again, Studebaker engine's are much more precise and clearances are much tighter so it needed to maintain a higher pressure to be happy.
kk