Low oil pressure

[Rapidtrans777]

Idle oil pressure at start up then after a 10 mile drive. It runs about 35psi @ 2000rpm when at operating temp. This is on fresh 10w-40. When I let off the gas it jumps 3-5 psi. It's been gradually getting worse to the point now where it definitely needs addressing. What do ya'll think? Time for a rebuild or could it be as simple as the relief spring in the oil pump? This is in my '70 Gran Coupe, original 383, mileage unknown.

 

[65sporty]

If that gauge is correct you have 66psi cold and 14 psi hot. I assume that's the 2 pic's cold and hot. 14psi at hot idle is ok

 

[Rapidtrans777]

I don't know how to label the individual pics, yes, the top is oil pressure at idle cold, second is idle at operating temp. I can watch it drop from 60 ish to 35 psi as I'm driving (it takes about 5 miles)as the water temp comes up.

 

[65sporty]

If the bottom pic with the 14psi is after the 10 mile drive, your oil pressure is good.

 

[Davea Lux]

14-15psi at idle is an adequate number, what is your idle speed? 35psi warm is about average as these stock relief valves were usually set to run at 35-40psi. You will have higher oil pressure with cold oil as the oil is thicker cold and does not flow as readily. I do not think your engine needs a rebuild. If you get a lot of knocking on cold starts before the oil pressure comes up, that is usually indicative of a loose main bearing set which on a well worn engine will cause low oil pressure as the engine warms up. If you are not hearing any of that you probably do not have a problem as your oil pressure appears normal.

For your own satisfaction, the next time you drain the oil, pour the contents of the oil filter over a dark cloth and look for metal, I bet you will not find any.

The other issue with low oil pressure can be poor quality oil filters. Some of the lower priced ones Fram in particular has lousy quality control and the insides of the filter will sometimes collapse, this will cause a big drop in oil pressure. Buy quality filters such as Wix or Hastings.

Dave

 

[CBODY67]

I have a Chrysler factory service manual for a '51 Plymouth a friend and I had grand plans for getting it running and reliable enough for him to daily-drive. In the section on oil pressure, it states that ANY oil pressure at idle is acceptable. Do the main oil pressure check at the stated rpm with the engine "hot".

When the '84 Corvettes came out, you could watch the oil temp readout as the engine warmed up (or any other desired time). I started it up and watched the oil temp rise from "cold". What I did notice was that the oil temp TRAILED the coolant temp in increasing. Engine was at "operating temp" in a few minutes, as normal, but the oil temp didn't get there until over 10 minutes later.

Perhaps if you want a definitive oil pressure check, you need a straight-weight oil, as SAE 30, as that oil doesn't have the same level of viscosity additives to make the multi-weight oil. "More stable", as they say. BUT with the posted results, you don't have anything to worry about.

CBODY67

 

[FURYGT]

NAPA Gold Filters are made by Wix and are another good choice. Not sure where you really are located, assume the Redneck Riviera is in a Southern state. If you are concerned, why not run a 15W30 or 15W40 oil. With an original engine with some miles on it, I have found that they tend to like the heavier weight oil. Also, make sure you are running a ZDDP additive or using an oil that has ZDDP in it. Personally, I like Brad Penn oil. It's a little pricey but it is a synthetic blend and has ZDDP in it and you can find it on eBay and Amazon and buy it by the case for a better price.

BTW, my street strip 520" with a high volume oil pump runs 65-70lbs cold on start up, 20lbs at idle and mid 30-40's when driving.

 

[Davea Lux]

The other advantage of a 15W40 oil is that configuration is an "all fleet" oil which means it still has the additives for iron valve guides and flat tappet camshafts used in diesel engines. Valvoline and the RPM Delo by Chevron are both excellent oils of this type.

Dave

 

[CBODY67]

The other advantage of a 15W40 oil is that configuration is an "all fleet" oil which means it still has the additives for iron valve guides and flat tappet camshafts used in diesel engines. Valvoline and the RPM Delo by Chevron are both excellent oils of this type.

Dave

As is Shell Rotella T 15W-40.

 

[sprice]

Rotella also has a 10w30 diesel engine oil. According to Shell Tech support, they have 1800 ppm of zinc in the Rotella Oils.

 

[Davea Lux]

Rotella also has a 10w30 diesel engine oil. According to Shell Tech support, they have 1800 ppm of zinc in the Rotella Oils.

Also good for those of you in deep freeze country.

Dave

 

[CBODY67]

Rotella also has a 10w30 diesel engine oil. According to Shell Tech support, they have 1800 ppm of zinc in the Rotella Oils.

There are SEVERAL Rotella T oils now. The dino 15W40, syn 5W40, a 10W30 for the "car" diesels, and semi-syn oils, too. Former model years of Rotella T did have closer to 1500ppm zddp, but with the more current ones, www.bobistheoilguy.com virgin oil analysis reports which have been posted there indicate closer to 1300ppm zddp, which is still above the "SL" level of 1000ppm zddp for "back then normal oils" on "car" diesel oils (think VW and Mercedes).

There have been some claims to not use a "diesel" oil in a gas engine, but I suspect the diesel-rated oils (diesel if the primary application) will have a little more cleaning additives. They all also have "car" oil ratings, too.

The sales network for Brad Penn oils has widened in recent years. I believe that Summit carries it, too?

A whole 'nuther subject for another time . . .

CBODY67

 

[Davea Lux]

1300ppm zddp is more than enough to make a 383 live happily for the foreseeable future. It only takes something like 900ppm zddp-1200ppm zddp, which used to be the formula for quality conventional oils. 1200 would be the better number, but the Phosphorus content which should be close to the zinc content in ppm. Classic motor oils also offers a high phosphorus/zinc oil.

Dave

 

[Rapidtrans777]

If the bottom pic with the 14psi is after the 10 mile drive, your oil pressure is good.

14-15psi at idle is an adequate number, what is your idle speed? 35psi warm is about average

Thanks, that's what I needed to hear. The service manual states 20 minimum at idle, 45-65@ 1000rpm, that's why I was concerned.

BUT with the posted results, you don't have anything to worry about.

Again, thanks for the reassurance.

why not run a 15W30 or 15W40 oil.

We run Mobil Delvac 15w-40 in our semis. I'll make the switch always have 20-30 gallons on hand. Looks like I'll be ordering some wix filters also.

The other advantage of a 15W40 oil is that configuration is an "all fleet" oil which means it still has the additives for iron valve guides and flat tappet camshafts used in diesel engines. Valvoline and the RPM Delo by Chevron are both excellent oils of this type.

Dave

Thanks for all the responses. Looks like a change in oil, better filter, and a new oil pressure gauge are coming up.

 

[FURYGT]

There is someone who sells Wix filters at a really good price by the case on MOPARTS.org.

 

[Rapidtrans777]

There is someone who sells Wix filters at a really good price by the case on MOPARTS.org.

Thanks Bill.

 

[Rapidtrans777]

1300ppm zddp is more than enough to make a 383 live happily for the foreseeable future. It only takes something like 900ppm zddp-1200ppm zddp, which used to be the formula for quality conventional oils. 1200 would be the better number, but the Phosphorus content which should be close to the zinc content in ppm. Classic motor oils also offers a high phosphorus/zinc oil.

Dave

Looks like the Mobil Delvac has 1000 ppm zddp so I should be good. Thanks, you guys are a wealth of information.

 

[BigblueC]

Don't forget about Valvoline VR1 oils. They're somewhere around 1500 ppm zddp and are on the shelf at Oreilly's (at least around here), and are available in straight 30, 40, 50, 60, or 10-30, 10-40, 20-50.

 

[Turboomni]

Don't forget about Valvoline VR1 oils. They're somewhere around 1500 ppm zddp and are on the shelf at Oreilly's (at least around here), and are available in straight 30, 40, 50, 60, or 10-30, 10-40, 20-50.

That's what I have been using and Wix filters. Good to hear the confirmation on the Valvoline VR1 oils.

 

[moper]

Given the age I would say the 14psi with 10wt is fine. Personally I run 15-40 fleet in everything, from the Hyundai to the Stratus to my 70s plow truck. SO go a tad heavier and keep an eye on it. The fact it's dropping slowly over time indicates the clearances are getting bigger. So figure on a convenient time to rebuild. But as it is now I would not consider it a "must do now".