Oil pressure below 1/4

[scottm]

At highway speed, 2000 rpm, the oil pressure is just above 1/4. It drops a hair below 1/4 at hot idle. I've not seen it reach 1/2. The dealer just changed the oil. Perhaps the gauge is wrong? Wishful thinking? It's going back to the dealer next week for the torque converter, good chance to get it looked at.

 

[DMX84]

I don’t like to base actual pressure on a factory gauge……it’s just for reference. If our LC runs normally at 1/2 and now it’s running at 1/4 than you can base some concern, otherwise you don’t have anything to go on, because it’s not that accurate. I would get a real gauge even if it just tempary to see what pressure your 1/4 scale reading is.
DMX

 

[scottm]

I mentioned my concern when it was in this week, they didn't say anything about it. I think the dealer should be able to check the pressure, maybe even correct the gage if it's off. If nothing else, it'd document an oil pressure issue when I first bought it, in case something goes wrong before the 100,000-mile warranty expires.

 

[cruiser100]

I don’t like to base actual pressure on a factory gauge……it’s just for reference. If our LC runs normally at 1/2 and now it’s running at 1/4 than you can base some concern, otherwise you don’t have anything to go on, because it’s not that accurate. I would get a real gauge even if it just tempary to see what pressure your 1/4 scale reading is.
DMX

x2. The stock gauge is not very accurate at all. The only thing it tells you, IMHO, is that you 'have' oil pressure. You'll need to get a good mechanical gauge to get a good reading and determine if you have an issue or not.

 

[NMuzj100]

These low readings are normal. If the oil level is correct then there is no reason to worry.

 

[scottm]

These low readings are normal. If the oil level is correct then there is no reason to worry.

My manual says "normal" is above 1/4-scale, so this worries me. Fresh oil has always yielded me higher pressures in other vehicles, so I'm wondering what the pressure will be like in 5k. I'm already seeing it drop in the first few 100 miles. Yes, factory oil pressure gauges are notoriously innacurate and designed to stay centered in the "normal" range while the real pressure fluctuates. But they are reasonably similar from truck to truck, and a significantly lower reading than other similar trucks is something that concerns me.

I've hooked up mechanical gauges on other vehicles, does anyone know if there's a convenient port for this on the 100? The truck goes back to the dealer on Wednesday for a new torque converter, I'll ask them to check the pressure with a mechanical gauge.

 

[NMuzj100]

If you search on the forum you'll find that several others have had the same readings on the dash gauge, checked with a mechanical gauge and found they had pressures within the normal range. At highway speeds it should get to the 1/4 mark.

The mechanical gauge is attached in place of the oil pressure switch right behind the oil filter. The oil pressure is only supposed to be above 4.3 psi at idle per the FSM (LU-1). At 3,000 rpm the range is 43-85 psi. Use locktite when reinstalling the switch.

At 5k your oil will still be new in the UZ engine.

 

[scottm]

Thanks NM, that's the info I was looking for. I thought I searched before posting, now I see a couple old threads on this. I've got a bunch of questions at once about this truck.

I'll have them check the pressure anyway, they should do it for free right now. I'll feel better, and have a good answer to anyone who asks about it, like if I ever sell it.

It'll soon have Rotella T Synthetic in it, once the dealer is done repairing stuff.

 

[Boston Mangler]

For what its worth:

Just bought a 99

When purchased, needle was at about 1/8 at idle and about 3/8 around 2500rpm

Just got done swapping over to Mobil 1 and its 3/8 at idle and between 1/2 and 3/4 around 2500rpm

My .02

 

[scottm]

Wow, what weight?

 

[Boston Mangler]

Wow, what weight?

Mobil 1 5w-30

 

[BOGH]

My gauge was 1/4 idle cold start and a little bit when was hot and at 200-2500 RPM a little bit bellow 1/2 measureted at -35C(-31F) + wind chill and now i have around 3mm more at 0C (32F).

I use only Mobil 1 5W 30 and in the cold time Mobil 1 0W30 on my cars.

Bog

 

[vak01]

Have a 99 also. VERY similar results on the OEM dash gauge. Also using Mobil 1 5W30

For what its worth:

Just bought a 99

When purchased, needle was at about 1/8 at idle and about 3/8 around 2500rpm

Just got done swapping over to Mobil 1 and its 3/8 at idle and between 1/2 and 3/4 around 2500rpm

My .02

 

[Nottajeep]

The mechanical gauge is attached in place of the oil pressure switch right behind the oil filter. The oil pressure is only supposed to be above 4.3 psi at idle per the FSM (LU-1). At 3,000 rpm the range is 43-85 psi. Use locktite when reinstalling the switch.

Has anyone ever tested this spec with various oil grades 0w, 5w, etc...?

 

[bamachem]

The dealer probably put 0W30 in it instead of 5W30. A lot of newer cars are designed to use 0W30 since it's viscosity is lower and *can* yeild a slightly better fuel efficiency.

I use Mobil1 5W30 Extended Drain with a 2X larger Mobil1 filter (for a Ford V6, believe it or not).

My oil pressure is ~1/4 or just above at hot idle and around 1/2 or just above at 2200 RPM. If I get on the skinny and get high RPM, it will shoot up to 3/4 and higher.

 

[NMuzj100]

0w-30 is the same viscosity as 5w-30 at operating temp.

And on a cold start still thicker than SAE 30 at temp. Different grades will have little effect on indicated pressure.

 

[OzKroozer]

Hi, I had a similar problem about a year ago and changed oil types etc and found marginal change in the guage. My UZJ100 has 210,000k on the clock and I tow a 2.5t caravan through rough country and usually when the ambient temperature is between 30-40c (86-104F). Then the guage strated fluctuating from 1/8 to 1/2 to 1/4 etc. I replaced the oil pressure sender and hey presto....all better. I realise that the factory guage is not precise but after testing etc the oil pressure was found to be good and that the sender was the problem. On recommendation from my mechanic I use Conoco Silver 20w-50. Because I live in drive in a fairly warm climate this seems to suit the LC well.

 

[NMuzj100]

On recommendation from my mechanic I use Conoco Silver 20w-50. Because I live in drive in a fairly warm climate this seems to suit the LC well.

The internal temp of the engine will be pretty much constant regardless of outside conditions.

Running a 50 weight oil has an effect similar to the oil never getting up to temperature. It will never be the viscosity the engine and oil pump were designed to operate at. A thicker oil means less flow, less flow means the oil can't cool the engine's internals as effectively.

From SAE J300, viscosities at 212 F...

20, range - 5.6 to 9.2
30, 9.3 - 12.4
40, 12.5 - 16.2
50, 16.3 - 21.8
60, 21.9 - 26.1
​

 

[NMuzj100]

Interesting PDF from Toyota back spec'ing 5w-20 and 0w-20 oils to many of their vehicles.

Doesn't list the Land Cruiser but the does approve 5w-20 in the 4.7L Tundra and Sequoia.

Note that these recommendations are for Toyota's Xw-20 oils which are more heavily moly-fortified than most on the market.

I won't be running any 20 weight in my 100 but this shows that trend is to take advantage of lower viscosities now that technology allows them to be effective at wear prevention.

Toyota Oil Application Chart PDF

 

[Nottajeep]

I seem to recall seeing oil on the 80-series board 4.5L I-6 spec'd at 20w-50 for the Aussies. Everyone seems to think the USA has lighter viscosity oils due to the fuel economy requirements. However, Toyota recommended the 20w-50 for the Aussies because they spec'd what is best for the engine not the fuel economy.