Auto-Rx lost some oil pressure

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Jan 14, 2009
I am now 1,000 miles into my initial clean faze with Auto-Rx. My vehicle is a 1990 Ford F150 w/straight 6- 300 engine with 52,000 miles total on it. Yesterday I noticed a small drop in oil pressure. I can't tell you what the exact pressure is because the cheap oil pressure guage isn't very accurate. All I can say is that I noticed it drop some. I am currently using some P.O.S. Fram filters for the Rx runs and have a couple Motorcraft FL1's on hand when the rinse faze is over. I'm hoping the Fram's cardboard endcaps aren't the cause. What do ya think? Should I be concerned? Should I change out the old Fram to a new one or trash them both and put on the Motorcraft? Or do nothing and not worry about it?
I would probably go with the Motorcraft Oil Filter instead.

I would just keep an eye on the oil level and not worry about this oil pressure gauge thing during the Clean and Rinse Phases.

Auto-rx is probably just loosening some junk up and that may be why you are seeing the oil pressure drop.

What brand of motor oil are you using for the Clean and Rinse Phases.

Fram Oil Filters do not have the best reputation on this board.
It is common for oil pressure to drop as oil shears out of grade in the first part of an OCI. That could be playing a part as well since I'm assuming you're using a garden variety dino oil as directed by ARX.
Yah, I'm aware of the Fram's rep here, but that's what I had on hand and that was before I climbed aboard BITOG. I am running 10W-30 Supertech oil for both Rx fazes.
Originally Posted By: ridgerunner
Yah, I'm aware of the Fram's rep here, but that's what I had on hand and that was before I climbed aboard BITOG. I am running 10W-30 Supertech oil for both Rx fazes.

Keep driving, and Good Luck.
Sometimes the oil sending units gets some false reads, when a lot of contaminants are dissolved and are on their way to filtration, resulting in somewhat false reads on the oil pressure telemetry. Where do you see the lower oil pressure, during idle or at cruising rpm ranges? That is a pretty low mileage unit for a 1990, should have many more years of service life.

If the motor sounds smooth, no abnormal sounds, I would say that the oil sending unit may have picked up some liquified crud, giving you a false read.

You could spin on a new filter if you think this filter may have collapsed and is in the bypass mode. There really should be no issue with oil pressure due to ARX in the oil, oil analysis shows that it does not affect viscocity of any 5 or 10 W 30 motor oils.
I noticed an oil pressure drop about 1200 miles into a Auto RX cleaning on a Nissan pick up engine that had a manual oil pressure gauge. I changed the filter and it went back to normal. I figured maybe the filter was getting clogged with with junk.
I kinda was thinking that the filter may be the cause, not too worried though. I'm going to change the old Fram filter out tonight and add a new Fram that I have lying around. I only need to run it another 1,200 miles (as of today) before I start my rinse faze. The rinse cycle I will use the Motorcrafts I have and call it good. I'll cut open all the filters to see what the Rx removed and see how the Frams held up. Thanks guys!
Is this an aftermarket gauge? Otherwise ..I think you've got an idiot light with a needle. Wasn't this one of Ford's better ideas?

If it is an aftermarket gauge ..just change the filter and see if it improves. Normally you should never see a filter alter the indicated pressure. If the sender is downstream of the filter ..the engine is what the engine is. The filter would have little impact on it assuming the oil pump is still pumping the same volume. If the pump is leaking (more than the normal, marginal, leakage) ..then a filter being clogged or loaded can alter the realized output to the engine ..and therefore can alter the reading (assuming all other things are equal- visc/temp/etc).

If the pressure sender is upstream from the filter, then it cannot be the filter as the cause. If anything, it would result in an increase in indicated pressure at the same volume.

Now a varnished or scored relief valve in the pump may be getting freed and you may see some intermediate alterations until it's done getting cleaned up.
Quick update. I replaced the old Fram with a new one and refilled w/ST 10W30. Oil pressure went down slighly more than before and remains there. Still within the "Normal" range on the needle guage. Truck's running great, no problems that I can see or feel. I cut open the old Fram and it looked pretty clean. Nothing out of the ordinary, cheap filter w/ few pleats and pleats that aren't uniform. Other than that, I think I'm good to go!
Ridgerunner, What did the drained oil look like? Likely fairly blackened. Let us know what the new oil, rinse phase, looks like after 1000-15500 miles of service life. Many times the rinse phase appears to remove more contaminants than in the "cleaning phase".
Yes, I added another 1/2 bottle of Rx with about 2 Qts of ST oil. The old oil on the dipstick looked real clean, med. brown. But when I drained out 2 qts. it was a dark brown, not black. Ya, I can't wait to get to the rinse phase, I'm driving this truck everyday now just to tally up the mileage! I've came to find out recently that I really love this old truck! My 07 Nissan X-terra looks a little ticked off at me for neglecting it this year.
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