Amsoil pressure drop after 3,500 miles

Circuit Rider

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I was going to suggest changing out the filter but too late for that. I see this a lot where someone purchases a used vehicle with unknown service history especially when going to a synthetic oil that it cleans a lot of the crud out of there and it all has to end up somewhere and luckily for you it was the oil filter and caught it in time before it could really do any damage.

Typically when I purchase a used vehicle and don't know the history I'll check the oil to see if it's been changed recently or not but when I do change it I mostly use Chevron Delo xle 10w30 which is a great oil and cheap too but if needs 0w20 or 5w20 then I'd use a good quality synthetic blend and monitor the oil consumption and change it out between 3k-5k miles. I'm usually not picky about filters but do tend to stay away from those orange cans but will use their other ones but I usually go with the oem filters such as AC Delco, Motorcraft, & Honda but also use Napa/Wix & Purolator.

Yeah. I checked the oil when I bought it but it was fresh. Bought it from a dealership; and they had changed the oil as part of their “pre sale service”. (I’m reasonably sure that’s the only thing they did, it was due for a lot of other stuff which I took care of when I got it home. Trans fluid, diffs, transfer case, brake fluid, etc.)

If I’m not mistaken, these had synthetic from the factory. If it was serviced at a dealer, it would’ve been serviced with an ACDelco branded synthetic. According to my brother in law who is a GM dealership tech.

AMSOIL said that they see this and it’s usually carbon, not sludge, that clogs up the filter. These engines just apparently produce a lot, according to them.
 
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Yeah. I checked the oil when I bought it but it was fresh. Bought it from a dealership; and they had changed the oil as part of their “pre sale service”. (I’m reasonably sure that’s the only thing they did, it was due for a lot of other stuff which I took care of when I got it home. Trans fluid, diffs, transfer case, brake fluid, etc.)

If I’m not mistaken, these had synthetic from the factory. If it was serviced at a dealer, it would’ve been serviced with an ACDelco branded synthetic. According to my brother in law who is a GM dealership tech.

AMSOIL said that they see this and it’s usually carbon, not sludge, that clogs up the filter. These engines just apparently produce a lot, according to them.
I guess right now is to try a different filter. I don't have any experience with the newer ones but I have an '04 GMC Sierra w/ 5.3 and a friend that also has basically the same truck but his is '08. I'm lucky mine is before they added all the afm stuff onto it, my friend has his disabled electronically but nothing has been done internally.
 
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Jan 16, 2021
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Hey folks!

Bought a used Chevrolet Tahoe (2014). Changed all the fluids when I got it, all with Amsoil. Amsoil Signature 10W-30 in the engine, Amsoil filter.

After about 3,500 miles (including a 1,200 mile towing trip) my oil pressure has dropped pretty significantly. From around 28psi at idle and 42psi under acceleration, to 19psi at idle and 35 under acceleration.

While that's still within spec for the engine; I'm curious the cause.

As an experiment I used a vacuum pump to remove a quart of oil and then added a fresh quart of Amsoil. The oil pressure returned to exactly where it was before. However within just a couple hundred miles, it was back to the 19 at idle / 35 under acceleration (28-30ish cruising) from before.

Is this a fuel dilution issue? I'm running E85 almost exclusively, I'm not sure if that has an impact. It's mostly two-lane 55mph road driving (I live in a rural area), and I rarely drive for less than 30 minutes. Just yesterday I drove 90 minutes each way. Wouldn't that get the oil warm enough to cause any fuel in the oil to evaporate? It is the max trailering model so it does have an oil cooler.

Other thoughts? Is this acceptable/normal behavior? Should I change now?

Thanks!
That's the filter loading issue, they are telling you to avoid extended drains. The filter should still be fine for more typical drain intervals. This is what I was alluding to with the mention of filter loading earlier in the thread, but it doesn't explain the return of the pressure when he added a fresh quart.
I would change it at 3000 miles snd just switch to a cheaper synthetic IMO. I have an 06 that if I try and go 5000 miles I loose oil pressure. I suspect it was neglected on maintenance by the previous owner because it has sludge and alot of it. I just use napa 5w30 synthetic and change it at 3000 miles even though I know the oil itself can go further.
 
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Don't worry, I wasn't implying you were in fact doing extended drains, I'm simply pointing out that the premise of extended drains hinges on an engine being in perfect health, and the oil and filter you are using are both designed for extended drains. That TSB from AMSOIL on the EaO was in reference to avoiding extended drain intervals with that filter in those applications because of premature loading to the point of bypass.

An oil with strong detergent chemistry and a filthy engine can of course lead to premature filter loading, which is my suspicion with respect to your situation.

You will need to cut and inspect your next few oil filters (I'd suggest posting pictures on here for the rest of us to look at) to monitor the loading if the first C&P confirms that this is what is going on. It should taper off once sufficient cleanliness has been achieved.
I been going back reading some of you guys "think tank, troubleshooting" escapades and your solutions. Gotta say for a while I had forgotten what brought me here. I am humbled by several of you. You guys simply hit it out of the park when someone comes here with a challenge or asking for help. I have to say I applaud many of you. Some of you should be teaching at vocational tech schools!!!:)🤙 Thanks cause I learn something new every time I read current and especially some older posts / discussions you guys have had.
 
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