Oil Cooler?

[Chevy305]

Ok so coming up in the fall I will be using the truck a lot more on the highway. And since I have no OD my truck spins at around 3000rpm which isn't the best for a long distances because my engine is getting tired.

Ok so yesterday I drove about an hour down the highway and the truck oil pressure was totally normal for it running between 20-25 while cruising and then when i get off the highway and hit a stop light I take note of my oil pressure around 9psi while idling. But on the return trip a few hours later after the truck sat, the cruising psi is the exact same but after I got home after the hour or so of 3000rpm cruising the oil pressure dropped quite a bit more so it was at 4psi or so. Its got me worried that it went that low. So I checked the oil and it was slightly low but that shouldn't have created a drop in the pressure. My thought was that maybe the oil was getting too hot because with normal use around town where 90% of my driving in done I have never seen the oil pressure go below 12psi. So maybe an oil cooler is what I will need to keep my oil cool for these long drives?

I run high milage 10-40 oil. Also I will need an oil change coming up soon if that helps...

 

[4X4HIGH]

Switch to 20-50 oil and your pressure will come up. An oil cooler will definately help a little as well. FWIW my rig has 235k on it and it still has 60+ psi of oil cold at idle and 55-60 hot and doesn't change much with RPM's

 

[Chevy305]

Maybe replacing my oil pump would help?

 

[dyeager535]

It *probably* won't. Low pressure is indicative of increasing clearances in the engine, and while the oil pump obviously is tied into pressure, more often on a high mileage engine, the pump is doing it's job, but no matter what, those clearances aren't getting smaller.

As mentioned, try 20-50. I've got an oil cooler setup on mine, and run 10-30, but it's a new motor. I'd really like to put a temp sender in the oil drain plug location to see how effective the cooler really is.

I'm not 100% certain, but it sounds to me like the oil coolers have a check valve/ball in them, they seem to hold oil for much longer than if they didn't have something like that.

 

[ntsqd]

None of the oil coolers I have feature anything like a check valve. What usually happens is capillary action won't let the oil drain very fast. Sort of like pushing the straw all the way into this lunch's drink, then putting your thumb over the end & pulling it out. You can control how fast the straw drains by how much air you let in at the top. The thicker the fluid the more air flow you need. The engine's oil galleys don't allow in much air.

 

[dyeager535]

My experience has been with them removed from the vehicle...Eventually at some point they seem to just drain all at once. Will hold oil for days, weeks, whatever, then come back and notice a huge puddle of oil.

I've noticed a rattling sound in a couple of ones that are "dry", assumed there was something like that in there since it wasn't just one that made the noise, coupled with the big puddles.

 

[Thunder]

Switch oil. 10-40 is about the worst oil to use IMO. It thins out too much and does not lube well at high rpm and temps. It is not recomended for most cars anymore. Use 20-50 as said, or 10-30. I perferr 10- 30 because it is a far more stable oil than 10 -40. the shorter the viscosity range the more stable the oil.
20- 50 also works well because it starts out with 20 weight oil as its base so it is thicker.

 

[Chevy305]

Wouldn't 10-30 thin out more than 10-40?

 

[Thunder]

Wouldn't 10-30 thin out more than 10-40?

Well not exactly, as long as you change oil regularly. Even tho it uses the same base 10 wt. 10 -30 is better because it does not contain as many polymers. As 10-30 ages it does not break down as fast as 10-40.
10-40 is a thicker oil when new but under hard use will break down faster than 10-30 leaving you with thin 10wt oil.
Polymers are what is added to multi vis oils that make it change viscosity. At room temp polymers are like tight little balls. As they heat up, they uncoil and and take up more space in the oil impeding the flow and causing it to thicken. Problem is with polymers is they do nothing to lubricate your engine.
Heat and shear break the polymers down. When they break down you end up with the base 10 wt oil with a bunch of broken down polymer gunk in it that does not lubricate your engine and aslo can cause the oil to foam.
10-40 has about twice as much polymers as 10 -30. When 10-40 breaks down it has less oil in solution to lubricate your engine.
So
Even tho 10-30 has a lower vis number it has a more oil in solution than 10-40. 10-30 has less polymers to break down and will keep its viscosity longer.

If you like 10-40. Switching to synthetic oil would also help you. Because it is formulated on a molecular level, it does not need polymers to make it a multi vis oil. I have switched from dino oil to syn in older high mileage engines and the switch helped a lot with keeping the oil pressure steady.

Running an oil cooler wouldn't hurt either. I run one in my k5. I like it.

 

[ntsqd]

Basically multi-grade oils violate, or at least severely bend, a law of physics. Sooner or later physics will win. An oil cooler can prolong the 'fight'.

Up until just recently I used straight 30wt. in everything. Maybe not practical for some locations, but here on the Left Coast (& I do mean On) it works fine. When I find an easy to buy source for it in gallon containers I'll go back to it.

 

[Chevy305]

Pretty informative!

I think that I'll jump up to 20-50 and see how that goes.

 

[Chevy305]

A little Update...

Pretty informative!

I think that I'll jump up to 20-50 and see how that goes.

Ok so I switched to the thicker 20-50 oil in my truck. Oil pressure is at a great level for driving around town. However, coming off the highway from cruising around 3000rpm for extended periods of time, the oil pressure still drops down to about 10psi when the engine gets back to idle speed and returns to that pressure whenever the engine idles again.

Would an oil cooler be able to fix this problem?

I'm thinking the oil gets really hot when I roar down the highway for extended periods of time and I am a little worried that when the oil gets too hot it will beak down and won't be able to protect the engine effectively.

 

[loafer]

Are you relying on the dash gage for these measurements?

Ok so I switched to the thicker 20-50 oil in my truck. Oil pressure is at a great level for driving around town. However, coming off the highway from cruising around 3000rpm for extended periods of time, the oil pressure still drops down to about 10psi when the engine gets back to idle speed and returns to that pressure whenever the engine idles again.

Would an oil cooler be able to fix this problem?

I'm thinking the oil gets really hot when I roar down the highway for extended periods of time and I am a little worried that when the oil gets too hot it will beak down and won't be able to protect the engine effectively.

 

[dyeager535]

I know where we're going with this, but...

His gauge shows pressure varying where it should. Likely it's working correct.

If using the stock gauge, you need to verify it against another guage to make sure it's reading right, especially in this situation where your oil pressure is already showing to be quite low.

 

[Chevy305]

Are you relying on the dash gage for these measurements?

I'm using an AutoMeter mechanical oil pressure gauge. And before that I was using an el-cheapo no-name brand mechanical gauge and it read about the same.

Would an oil cooler be able to keep the oil cool enough to give me maybe a few extra psi?

 

[ntsqd]

What's you oil temp now?

 

[Chevy305]

What's you oil temp now?

I don't know, I don't have an oil temp gauge.

Maybe I'll get one and then see if the oil starts getting too hot. But uh, What temp is too hot for oil?

 

[4by4bygod]

Glenn.. did you ever replace the oil pressure switch?

I had to change the one on my 87 K5 that had a 305 ( and over 200,000 miles on it ).. the factory gauge would read just like yours does..normal at cruising speed, and 10 or below when I came off the freeway. when the switch gets fouled, they can give off all kinds of goofy readings.

As far as the oil getting too hot and giving you the low reading, I wouldn't worry about that since the oils too new..I'd say your issue is definitely mechanical of some sort, and not fluid related..

 

[Chevy305]

Glenn.. did you ever replace the oil pressure switch?

I had to change the one on my 87 K5 that had a 305 ( and over 200,000 miles on it ).. the factory gauge would read just like yours does..normal at cruising speed, and 10 or below when I came off the freeway. when the switch gets fouled, they can give off all kinds of goofy readings.

As far as the oil getting too hot and giving you the low reading, I wouldn't worry about that since the oils too new..I'd say your issue is definitely mechanical of some sort, and not fluid related..

I don't have a stock gauge... This is how my dash looks:




You know I would prefer it to be fluid related...

Oh and a little HIJACK in my own thread:
Tom: I just calculated my milage yesterday while I filled up and I hit 10.5!!! Thats about 25% better milage off the ACES IV!!!

 

[ryoken]

You'd be amazed what an oil temp gauge shows you...

Too cool an oil is no good, engine oil actually gives better performance and power at higher temps, up to about 240, 250.. Not uncommon to see a motor under hard load go 10% above water temp.. That being said, it is hard on oil and breaks it down quicker..

Generally with my 195 therm, I run around 200 water temp. while cruising around town, oil temp'll run 180ish.. When beating on it, it'll go upwards of 225.. Which is about as high as I like to see..

My pressures pretty much remains the same, warm or hot...