That's what I do with my mower, it gets the widow and orphan oils. The power washer, snowblower, and generator all get Mobil 1 0W40 now, my Mobil 1 Turbo Diesel Truck 5w40 supply has been depleted.
Don't mix oils! Oil pressure dropped ---
- Thread starter 70GS455
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Does a difference of 4 or 5 psi really even matter when it's already in the 60s?
OVERKILL
$100 Site Donor 2021
Air bubbles in bearings can do bad things, so yes, I think if what we see is aeration, that it does matter.
This looks like aeration to me. At higher RPM the oil is getting whipped around creating bubbles. Pressure is reduced because the air bubbles compress. Aerated oil heats up faster too.
In a performance engine this is usually mitigated by a crank scraper and an oil pan designed to get the oil out of the way to prevent the rotating assembly from slinging it everywhere and trying to whip it into mayonnaise. Internal panels, kickouts and screens usually help.
On the dyno this is a unique problem that may or may not show up in real life. In real life under full straight-line acceleration the oil is going to be in the back of the pan. Depending on the make/model/engine that may be good, totally submerging the pickup but if the pickup is up front that can pose a different set of problems. Road racing requires a different type of pan to help keep the oil from going everywhere and to keep the pickup submerged.
On the dyno a simple way to test if it is an aeration problem is to reduce the oil level by 0.5qt or so and run again. I'll bet you the pressure drop goes away at some point. Now you have to ask yourself if you want to run your car with 4 quarts in a 6 quart sump? The answer is usually no....the solution is a better oil pan/scraper setup.
What engine are you dyno'ing? Anything special about the oil pan/pump?
In a performance engine this is usually mitigated by a crank scraper and an oil pan designed to get the oil out of the way to prevent the rotating assembly from slinging it everywhere and trying to whip it into mayonnaise. Internal panels, kickouts and screens usually help.
On the dyno this is a unique problem that may or may not show up in real life. In real life under full straight-line acceleration the oil is going to be in the back of the pan. Depending on the make/model/engine that may be good, totally submerging the pickup but if the pickup is up front that can pose a different set of problems. Road racing requires a different type of pan to help keep the oil from going everywhere and to keep the pickup submerged.
On the dyno a simple way to test if it is an aeration problem is to reduce the oil level by 0.5qt or so and run again. I'll bet you the pressure drop goes away at some point. Now you have to ask yourself if you want to run your car with 4 quarts in a 6 quart sump? The answer is usually no....the solution is a better oil pan/scraper setup.
What engine are you dyno'ing? Anything special about the oil pan/pump?
Air bubbles don't lubricate well. And even when the bubbles compress under pressure you now have "less oil" which can lead to inconsistent oiling on bearing surfaces.
Probably not a big deal on grandma's car that only goes full throttle once a year (if ever), but it a high performance engine that spends lots of time at RPM it can lead to wear.
I'll take my chances.
You may be correct about it aerating due to crank churning the oil. We are still testing so I can try to lower the level (we noticed later in tests that the 100% Mobil 1 0W40 still dropped about 2 psi only when the oil was like 240F). The engine is a Buick 482, makes 610 ft lb/ 600 hp. The pan is an extra qt pan, had a louvered close-fitting full-length tray, no scraper, no kick outs and the front part is closer to the crank than I would like (on par with stock pan or slightly less). Here is a video of a dyno session
@70GS455 Nice engine! Even if you do find the magic oil volume / viscocity combo... that only proves that you fixed it on the dyno. You'll probably never completely solve this once the car is in motion and oil is being forced one place or another.
Do the BBC parts swap over to BBB's? Maybe a crank scraper and oil pan upgrade is in order. $$$
Moroso Drag Race Pan
Do the BBC parts swap over to BBB's? Maybe a crank scraper and oil pan upgrade is in order. $$$
Moroso Drag Race Pan
Thanks. Unfortunately no, those things would have to be modified to fit.
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Lol at thinking every drop of oil is removed from the system with one or even a few oil changes. I probably have remnants of 20 different oils left in my engine.
I wonder how Quaker State All Mileage 5W-30 would've behaved on its own (this particular oil -or even batch - may have been the contributor to the supposed aeration of OP's mix).
I generally avoid mixing but I have many times and would not be worried if I needed to do it again (engine oils).
I generally avoid mixing but I have many times and would not be worried if I needed to do it again (engine oils).
wemay
Site Donor 2023
I think we're all jumping the gun blaming this on mixing oils.
Especially when those hot bubbles POP in the bearing!
Agreed. The whole thread is like that.
I agree, I think mixing is getting a bad rap. I also think air bubbles is the culprit here. Having said that the only ICE engine I own that gets mixed oil is my lawn mower, and that isn't that often.
Very non-scientific. Did the OP cut the original filter apart?
I did but nothing stuck out as unusual
So I noticed the issue only appears at elevated oil temperatures. From room temp to 230f oil expands about 7% or in my case almost half a quart. We are testing again soon so I will take out a half a quart to start with and see how it goes. That may be the real issue (windage and aeration from the crank)
dnewton3
Staff member
There is no credible position to blame the oil, or the filter. This is an anecdotal experience story.
No baselines or controls were established, and when multiple variables (oils; filters) are changed simultaneously, any ability to assign causation flies out the window. Shannin RedX root cause analysis could be applied, but the reportedly offending products ( the actual same oil and filter) would need multiple trials back-to-back, in a designated DOE matrix.
No baselines or controls were established, and when multiple variables (oils; filters) are changed simultaneously, any ability to assign causation flies out the window. Shannin RedX root cause analysis could be applied, but the reportedly offending products ( the actual same oil and filter) would need multiple trials back-to-back, in a designated DOE matrix.
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