synthetic oil cleaning out a high milage engine?

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Hi All! I've heard that running synthetic oil in an older engine can loosen lots of crud to get in the filters.... Here's my little story... I own a '94 Chevy K3500 with a 5.7 in it with just over 200K miles on it. Last year I had the engine out to fix a cracked frame, and while the engine was out, on the stand I opened it up and washed it as well as I could by filling it with diesel, sloshing it around and draining it out, twice. I installed a new melling high volume oil pump and then did a filter relocation to the upper left corner of the engine compartment, and upped the filtration from the small stock spin on to a pair of Wix 51515 filters, connected to the block by three foot braided 1/2" lines..... After a lot of reading, here, I decided to switch to a full synthetic oil, last fall, to avoid pushing thickened oil through those filters during a cold Montana winter.
Everything was working just fine. I had no leaks and good oil pressure, and the system wintered well. Then, just a couple of weeks ago, after less than three thousand miles, I started the truck one morning and watch the oil pressure dump! Nothing on the dip stick (out of 7 total quarts in the system) and probably less than a quart in the engine when I drained the sump. It seems that the filters had plugged up and caused a pressure spike that was puking oil out from around the "O" ring in the adapter on the block. (this is after several months of driving daily with no sign of leaks or oil loss). Thankfully, I caught the problem in time and suffered no damage. I changed the filters (but didn't think to cut the old ones open before I tossed them) and the oil and the problem has not recurred in a month of daily use. I installed two sending units on the filter inlet and outlets, and ran them to a switch and a (Dakota) digital oil gauge. The gauge off the back of the block, and the filter inlet show the same pressure, within one pound. The apparent difference at this time, between the engine pressure and the OUTLET of the filters is about two pounds on the new filters. So, I'm looking for two things: Weather or not it is a true fact that putting synthetic oil in an older engine can and does loosen enough gunk to clog filters, and secondly, does anyone have any info on what might be a "normal" spread between filter inlet and outlet pressures as a filter loads up? I would like to go back to synthetic before winter, this fall, and would surely like to avoid a repeat of my problem.... Great site, and thanks, in advance, for any input!
 
Did you do any sort of chemical engine flush? i know somebody who did an engine flush on a really high mileage motor that had been run on Dino with not very frequent oil changes and the result was the gunk blocked the oil pickup screen, the engine lost oil pressure, and it required a full rebuild...
 
It might be worth running a good HDEO with a seal conditioner (do you get Forte products in the US?) for a few OCI to make sure everything is squeaky clean before moving over to a PCMO Group 3/4 synthetic.
It's my plan with the Land Rover Defender I have. 20 years old with 77k on the clock that has always been run on dino oil.
 
WHAT? On a 350?!?!

The little aluminum thing that mounts on the block with two bolts and has threads for your oil filter (or oil filter adapter) is the filter relief. If the is ANY excessive pressure in your remote system..... the oil just goes through the hole in the relief.

What you are describing as the "fault" in 100% inaccurate:

"It seems that the filters had plugged up and caused a pressure spike" = total baloney.

The most likely problem is the cheap and poorly machined adapter from Perma-cool (or whoever) that threads on where your original oil filter was. It's probably not machined flat.

The other possibility is some chowder-headed donkey added extra washers to the oil pressure relief spring in your new melling HV oil pump. Drop the oil pan and put it back like it was.
 
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Originally Posted By: MontanaAndy
secondly, does anyone have any info on what might be a "normal" spread between filter inlet and outlet pressures as a filter loads up?


Unless you like a lot of throttle when the oil is cold, there's not much spread.
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3197094/Differential_Pressure_Data,_Pu#Post3197094

With dual 51515's, they should NEVER go "into bypass" (7-9 psi).

1-2 psi will be normal 99.99% of the time
 
I've been using synthetic oil for 17 years or so. The engines are clean, don't move off the full mark and don't leak. My DD is 17 years old, has 288k miles and is fine. Your engine has some other issues.
 
The GM 5.7L 350 engine was put in many cars and trucks and by Mercruiser in many boats. Rock solid engine if maintained decently.

Why would you add what you what you did to a 1994 engine? You did not even add a bypass filter which might benefit your engine. Might!
 
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That's one heck of a story!

I've never seen a synthetic act as a detergent so great as to plug filters with pre-existing
junk.

I know that kerosene as an engine oil flush in old oil in a dirty engine idled for 30 minutes
has pulled out lots of dirt and drained straight into a pan then change the filter and oil
and you're good to go with no worries.

As posted there's gotta be other problems that got overlooked, like eyeballing every new part
added to see if a manufacturing defect is the root cause.
 
OK, I get extra filtration. I'm a big fan of oversized filters when they can be physically fit in place. And that would have been my move - a single oversized on the stock mount ...

But I got issues with your diagnosis. I get using a HV pump at 200K. The clearances have opened up enough that the extra flow is good. But I don't get the dual filter set-up. Is this two filters in parallel so each sees a portion of the incoming flow? Or is this a series arrangement so you run a coarse filter first and fine filter second?

O Ring failures can happen anytime. They happen on tractors when you are at the bottom of a pit and can't get at them, usually. But I can't see a new one just blowing out. Unless your block by-pass is plugged?

So describe your filter arrangement a bit better and we can take a shot at the differential pressures you should see ...
 
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Originally Posted By: MontanaAndy
I changed the filters (but didn't think to cut the old ones open before I tossed them) and the oil and the problem has not recurred in a month of daily use. I installed two sending units on the filter inlet and outlets, and ran them to a switch and a (Dakota) digital oil gauge. The gauge off the back of the block, and the filter inlet show the same pressure, within one pound. The apparent difference at this time, between the engine pressure and the OUTLET of the filters is about two pounds on the new filters.


Under what conditions did you see the 2 lbs delta-p (ie, hot oil, cold oil? ... idle, high RPM?) The delta-p across the filter is dependent on the oil viscosity (temperature) and flow rate (engine RPM) ... like this:

5W-30 @ 200 deg F.



Originally Posted By: MontanaAndy
... does anyone have any info on what might be a "normal" spread between filter inlet and outlet pressures as a filter loads up?


The graph above is on a new filter, so as it loads up the whole curve will shift upward giving a higher delta-p for each flow rate.
 
Thanks for the replies, guys. I bought this old truck for a work rig around my place. About a year ago, I found a study (on-line) that the state of California did in small, medium and larger trucks, using oil analysis and different filters, there were able to successfully go to 15,000 miles between oil changes using filters that removed smaller particles. Now, I'm kind of an old iron guy. The '94 is the newest truck I've owned. Trucks are projects to me. This engine has just over 208K on it, and ran well. I did not like the small stock filter. I decided to change to more filtration by using two series run filters (but hadn't thought of using two different levels of filtration.) I used a Canton adapter plate, and put the filters in an easy accessible place, as I'm getting near 70, and don't seem to bend as easily as I used to. I spent nearly 30 years as a licensed engineer on sea-going tugs, and I'm the "chowder headed" gent that did all the work.....Properly... No, I did use no additives. I used no engine flush other than washing the engine out with diesel while it was on the engine stand. Twice. I then ran a Castrol synthetic blend through for a 3000 mile cycle, as I have been doing with all of my vehicles for the last three or four decades. At today's prices, I was attracted to the idea of only having to do one oil change a year, instead of two or three. My other goals were to increase the amount of filtration by something like 60% and add 2 more quarts of oil to the system., I used a high pressure spring in the pump because my hot idling oil pressure was lower than I liked. Probably a bias of mine from many years working on engines like EMD's, big Cats and such, where the oil systems are much different and run more pressure. I ran the truck with this system for half a year with no oil leakage, and had to add no oil between changes. As it sits, now, I have a cold oil pressure, at 1500 rpm (the truck idles fast until it begins to warm up) of 68-70 psi. At 218°F oil temp (Yes, I also run an oil temp gauge), I'm running about 40 psi at idle, and 64 psi at 22-2300 rpm. I decided to go with full synthetic, last fall because it doesn't thicken at cold temps (and Montana winters tend to get cold), and I figured that would more beneficial(didn't want the filters to become the weak link) than pushing cold oil through filters and plumbing. I typically am pretty careful about warming the engine water temp to above 100° before moving the vehicle, and then idling down my 3/8 of a mile driveway while the oil begins to get warm. By the time I reach the road, the oil temp has usually hit that 100° mark.
Again, all winter the truck ran without leaks or other oil loss. This problem seemed to happen suddenly, as I have not seen any oil on the ground where I park in front of my house. When I found the problem, the only evidence of leakage was around the Canton adapter plate. Once I changed the filters and oil (back to a 5-30 Castrol mineral based oil), the problem went away and I have found no evidence of further leakage, and have had no oil level change on the dipstick, after, oh, a couple of hundred miles of driving. Logic seemed to point to clogged filters, especially since fresh filters made the problem disappear. I spoke with reps from Melling and Wix, and am sure the higher volume of flow is within specs for for the pair of filters. I'll have to add, here, that this was the first time I have used a full synthetic oil(ever) and the Wix 51515xp filter. Which made me ask the question about the possibility of the synthetic loosening up enough gunk to actually be a cause for the problem after about six months of driving. I know the filters, when I removed them, seemed to be heavier than I had expected, too. Though I felt that the diesel flush I did while the engine was out removed a LOT of crud, I can't discount the possibility there was more left in there... But SOMETHING happened to push oil past that O-ring without blowing it out. For now, I'm just monitoring the system and keeping a good eye on the actual pressure differential across the filters... Again, thanks for the input, all.....
 
If you want to have really extended oil changes, go back to one regular filter and add in a bypass filter. This will seriously extend your OCI. There is a complete subforum here that covers more detail than I can type on a phone.

I will let others chime in on the failure, but I would think a block bypass would keep the engine running even if the filters got fully plugged. If they are the same specification filter run in series, the first filter would plug first and the second would be relatively new or at least useable.
 
Originally Posted By: MontanaAndy
I used a high pressure spring in the pump


AH HA!! I knew it!! That is where you futzed up!

TAKE IT OUT - - the spring was *NEVER* intended to be married to a high volume oil pump.

I hope you didn't throw away the spring that came with the HV Melling oil pump - - that is the one the BELONGS in there.
 
Gee! the high pressure spring came WITH the oil pump FROM MELLING... In the same box! I woulda thought that the company that designed and built the pump might have known what their product should run.... They even mentioned it in their little installation pamphlet......
The bypass filter idea is new to me, and I'm checking into that! Thanks for that!
Andy
 
Originally Posted By: MontanaAndy
I used a high pressure spring in the pump because my hot idling oil pressure was lower than I liked.


I see this a lot and I still don't understand it.

The relief valve and associated spring is there to prevent *excess* oil pressure. So it *limits* the maximum pressure the pump can develop by relieving at a high pressure. How on earth is that going to *increase* low oil pressure? If the pressure is low, the valve will be closed anyway. Put a heavier spring behind it all you like, it's still closed.

Am I missing something obvious?
 
Originally Posted By: MontanaAndy
the high pressure spring came WITH the oil pump FROM MELLING... In the same box!


I will not believe this.

I have bought well over 100 HV oil pumps from Melling over the years,
and there has never, ever, ever, ever, been any "extra spring in the box".

Ever.
 
Originally Posted By: Linctex
Originally Posted By: MontanaAndy
the high pressure spring came WITH the oil pump FROM MELLING... In the same box!


I will not believe this.

I have bought well over 100 HV oil pumps from Melling over the years,
and there has never, ever, ever, ever, been any "extra spring in the box".

Ever.


^^ tell us how you really feel, Linc---don't hold back j/k
Excellent diagnosis I will add
Steve
 
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