alconk

iTrader: (1)

I have a 94 Z with 150,xxx miles and still runs awsom but I have noticed the oil pressure is starting to drop a little. When warm it used to be about 40 running down the road but now it's under 40 psi by the gauge. And at idle it's only about 20 psi. I don't plan on a rebuild for awhile because of low funds but thought about changing weights of oil. I've been running 5W30 Mobil 1 but thought about 10W40 or even 20W50 but thought that might be too think for the winter. Any thoughts would be appreciated.

1pissedoffliter

Just change your oil for now. I never liked mobil 1 in these cars. But that is just my opinion and you know what they say bout those. But if your pump is going out it will only buy you time. Start with 10-40. Then when that stops workin then 15-50. Then when that stops then go with 15-50 and lucas.........

alconk

iTrader: (1)

So you think the pump is getting weak and not the bearings wearing out? How good is that Lucas oil? I really haven't heard that much about that company. What brand of oil do you use? And in your opinion what brand do you think LT1s run better on??

buffman

iTrader: (9)

Bahh with the lucas oil additive crap. 20psi oil pressure @ hot idle is not low oil pressure by any means. M1 5/10w 30 oils are not the thickest 30 weight oils around. They measure only slightly better than average viscosity than most 30 weight oils. Try some 10w40 if you want, or German Castrol 0w30 (available at most autozones will say made in germany) is a really thick 30 weight.

I would personally pick up a mechanical oil pressure gauge if you'd want to really know what your oil pressure is, if you're that concerned about it.

1pissedoffliter

I have built a lot of engines and played with a lot of different engines. And let me state this is just my opinion of what I have seen. So I dont want to turn this into a huge debate or bashing thread. But it seems to me that on LS and LT engines that they do not like Mobil one. Just from the bearing wear I have seen, and just from when the oil comes out on how thin it gets so quickly. Maybe it is because of the slightly added clearance of the Lts and Ls. Or maybe it is because of the torque these engines produce. Maybe they like the extra cushion of thicker oil. My route I have always stayed with is the use of regular motor oil, not synthetic, and change the oil more often. It breaks even in pricing and has not let me down.

And bearings wearing thin will not cause your oil pressure to drop. Do you have a front or rear main leak? Also, oil pressure will always be lower with synthetic oil, because it is not as thick. However that does not mean you have less oiling, it just flows easier, therefore does not produce as much pressure moving.

1pissedoffliter

Oh yeah, never said I liked lucas. Just saying it will raise your oil pressure when all else fails.

alconk

iTrader: (1)

Oh ok, didn't know that LTs didn't like synthetics. All this time I thought I was doing good for it. My engine does not have any leaks. I've been thinking about a mechanical gauge but I'm not sure where I can tap into it. All I was concerned was that I have noticed a drop in pres. and didn't know if something serious was happening.

alconk

iTrader: (1)

Would you reconmend installing a new pump??

ZEX-Z

iTrader: (4)

I would install a new oil pump. Clean out your oil cooler because it can get plugged with crap......+ does the oil pressure drop real low when you stop or slow down real hard. If it does, with the miles you have........ You've probable have a little bit of clearance in your bearings due to high milage. Nothing last forever. No matter how good you treat it.

aboatguy

Bearing wear will cause oil pressure drop.,

I'd like to see the scientific study showing LT1s don't like Mobil 1?

Since it was the factory fill on the LT1 Corvettes.

Matts94Z28

iTrader: (6)

If the pressure has been going down gradually it could be the oil pressure sensor. Over a period of 6 months i lost about 10-15psi all around and it was just a simple sensor going bad. It should be located on the back of your block unless you have an early 94 then it will be above the oil filter.

But then again i have to agree that the pressure seems normal for a 150k mile motor, Hell i have 45k on my 355 and i run about the same pressure.

seawolf06

iTrader: (8)

If you have an oil cooler, take that POS off first. It's really easy and it's a very common problem that causes low oil pressure.

transam5.7lt1

iTrader: (18)

That oil pressure at idle is normal in a sbc, worry about it when given acceleration and the needle won't climb. Synthetic oils don't work well in high mileage motors, they're factory fill oils because of marketing reasons, not to take any credit from them, they worked well when LT1s used to be fresh motors with little to almost no miles. In high mileage motors synthetic oils don't build the same oil pressure, they can even create oil leaks.

1pissedoffliter

^^^^^^^^^^^^^^^^^^^^^^^^^^^^This is to ABOATGUY, how much more clear can I state this fact. And let me know how bearing wear can drop oil pressure. If it does then it will only be just a smige. Just because more oil can travel through the bearings. But not as much as he stated. I mean a couple thousandths more clearance than factory, ya done spun a bearing.

buffman

iTrader: (9)

That's some big serious BS right there

Now M1 oils in the 5/10w 30 flavors do not like lt1s and ls1s because it's a generally "thin" oil based on where it falls in the 30 weight range refering to viscosity @ 100c. You'll find much better wear #s when doing a used Oil analysis if you switch to a better oil.

I'd have to agree M1 was used in vettes for marketing reasons and the fact that synthetic oils tend to take the abuse of higher oil temps better than convential. Without a factory oil cooler, vette's can see some fairly high oil temps.

That being said, You need to hookup a mechanical gauge and verify oil pressure before worrying. You can tap in the back of the block up by the intake, or above the oil filter in the block, or even in the oil filter adapter itself if it has a plug..

Im not sure when they changed it, but I thought F-car oil coolers, routed actual coolant back to the sandwich adapter between the filter and the block?

Also note that unless the M1 oil is fresh, it shears over time, aka looses viscosity like some other oils. SOme of these guys have you worrying about nothing... I think bare min oil pressure per FSM is 1 psi per 100rpms, or roughly 10-12psi @ idle..

omaha stylee

where do you live? i have noticed in the winter (chicago by the way) my oil pressure is always lower. Guessing maybe the temp for me? just a thought

buffman

iTrader: (9)

I live in southwest Michigan. Oil pressure should be higher when cold..

omaha stylee

that is what i figured because in theory being colder it would be thicker....I dunno why mine is lower in the winter "scratching my head"

buffman

iTrader: (9)

get mechanical oil pressure gauge and check oil pressure. dont trust stock gauge

transam5.7lt1

iTrader: (18)

How dare you call BS on me, I am saying synthetic oils don't work well in high mileage motors from experience. I tried synthetic oils, different brands and all they did was create oil leaks... I am telling you not just from my point of view or expiernce with them, but from the stand point of many friends that had similar symptoms from using synthetic oil. Don't take it personal, but I and many do believe that synthetic creates problems in high mileage engines. By the way, we are in Texas, its always hot down here, maybe in a colder environment, sythetic would work for us......for now... we'll stick to regular oil at 3,000 mile intervals...