Loosing Oil Pressure

[66Sprint6]

Well, when I first start the car my oil pressure gauge (autometer) reads 35-40psi. Once I drive around a bit, it goes down to 15psi!!!!! Whats that all about? Im not sure what to think about that. Im goin to go check it out in a few, today has been a rough day. Just got it back from gettin the T5 installed and now the heater hose has sprung a leak and the oil pressure is dropping
Oh well, hopefully I can work all the bugs out soon
Matt

 

[Anonymous]

If the oil pressure droppe suddenly, like yesterday it had like 50 psi, I would worry. My brother's 400M has no oil pressure, I mean zero whenever its warm, and it runs like champ.

 

[MustangSix]

Oil pressure that starts high and drops as it warms is indicative of worn bearings with too much clearance.

 

[66Sprint6]

Dang, how big of a deal is this? How hard or expensive would it be to fix, and should I worry about driving it like this? I really cant afford to mess with this right now dangit, but its just starting to happen. I had pretty steady oil pressure, then I got the 5 speed put in and it was a little low, 25-30psi. The mechanic then resealed the oil pan (had a nasty leak) and put in new oil and now my pressure starts out at 35-40 and drops from there.
Matt

 

[66Sprint6]

Just drove it...
Started out at about 40psi, then once it got a little warm, it started dropping. After a good 30-45 minute drive, it was at 15psi, but when I would get the RPMs up, it would hover around 25-30 psi. Dern it, its one thing after another!
Matt

 

[pedal2themetal45]

HI
When you run a multi grade oil when the motor warms up the oil thins out thus lowering the oil prusher as the thinner oil well exit clearances quicker thus lowering prusher. Say if your running a 10-40 oil go and don't like the prusher at idle go with like a 20-40 or 20-50 and the idle pursher well go up..
OH as long as it runs about 15 - 20 lbs I wouldn't worry about it. My new 466 well run 75 cold the drop to 30 warm.
Tim

 

[66Sprint6]

That sounds promising, and one thing I didnt think of is...the motor runs perfectly fine, no knocking or ticking at all when the oil pressure drops. Also, when I checked the oil, it seemed really really thin, if that makes any sense at all, so maybe thats whats doin it.
Matt

 

[strat1960s]

When I had my motor rebuilt, the owner of the machine shop told me to run straight 30 wt during the winter and straight 40 wt during the summer. He also said he prefered using Valvoline racing motor oil because it had anti-foaming agents in it. My oil pressure has been at or around the 30 to 40 PSI mark. When I get to an intersection and I have to stop the oil pressure does drop a little, but the car is supposed to have a minimum of 20 psi. Maybe, by going with a thincker single grade motor oil you would get more consistent PSI readings on your guage.

 

[66Sprint6]

I added some Lucas oil additive and got a 5psi higher pressure when it drops, but who knows. I do know that whatever oil the shop put in, it is THIN on the dipstick, so maybe that has to do with it.
Matt

 

[Lazy JW]

Heavier oil will probably help. Air-cooled Volkswagens are famous for low oil pressure when they get worn. My 68 Bug has over 100,000 miles on this engine (pretty high miles for a Bug) and in the summer I run 20w-50 oil to keep the idiot light from coming on at idle after it has warmed up. Those idiot lights don't turn on until the pressure drops to about 3 psi With the 10w-30 oil I have to keep it idling above 1000 rpm to keep the idiot light from winking at me. This engine runs fine, has good compression, no knocks, just low oil pressure. The proper cure is to rebuild it and tighten up the loose bearing clearances, but it will have to develop some other problem first as long as heavy oil will keep it going. The 300 in my truck has never shown as much oil pressure as the worn out 360 that was originally in it, but the 360 used lots of oil and the 300 doesn't. The same (factory) guage was used on both engines, but different sending units. The factory guage has no numbers on it, but the 360 operated at about 2/3 scale and the 300 runs at about 1/3 on the scale. I use 20w-50 in the 300, the 10w-30 only showed about 1/4 scale on the guage. Unless you are revving pretty hard (racing?) I wouldn't worry about the readings you are getting, it should run a long time like that.
Joe