Amsoil pressure drop after 3,500 miles

Circuit Rider

Thread starter
Joined
Sep 19, 2021
Messages
25
Hey friends!

My metal snips are AWOL. Looked all over! I recently moved and fear they didn’t move with me.

I’ll order some more. When they arrive, I’ll show you guys the inside of the filter.

I sent Amsoil an email about the discrepancy in their recommendation for 2013 and 2014 models (which are the same thing despite different recommendations on their website).

They confirmed the behavior is consistent with that they tend to see on the 5.3’s and that 2-3k is all they seem to last. He suggested it was actually excessive carbon buildup caused by AFM.

I’ve got two pushbacks on that particulary theory. 1.) I’m using E85 almost exclusively, so carbon buildup should be minimal. 2.) I have AFM disabled and have since I bought the truck.

To my surprise, they also said they were going to refund me the purchase of the filters. That’s super generous. Certainly don’t expect that; the issue isn’t with the filter it’s with my engine.
 

Circuit Rider

Thread starter
Joined
Sep 19, 2021
Messages
25
Why do you use E85?
Fewer emissions, cleaner burning in the engine (less carbon buildup, can actually help remove carbon and other deposits from within the engine), additional horsepower and torque, importing my fuel from Iowa instead of OPEC, etc.
 
Joined
Sep 11, 2021
Messages
234
Fewer emissions, cleaner burning in the engine (less carbon buildup, can actually help remove carbon and other deposits from within the engine), additional horsepower and torque, importing my fuel from Iowa instead of OPEC, etc.
Same amount of emissions when the lower fuel mileage accounted for. Considerably lower power. Engines run on unleaded fuel hardly have any carbon or other deposits. We do not import much OPEC oil these days.
 

Circuit Rider

Thread starter
Joined
Sep 19, 2021
Messages
25
Same amount of emissions when the lower fuel mileage accounted for. Considerably lower power. We do not import much OPEC oil these days.
In what world is 326hp “considerably less” than 320hp? Or is 348 ft/lb “considerably less” than 335?

While it can vary based on platform (I don’t run E85 in my Focus for example), the 5.3 from GM takes advantage of the very high octane rating of E85 and makes more power with it. Power is the most common reason people use E85. While there’s less energy in a quantity of E85 than a quantity of gasoline (hence the poorer fuel economy), the high octane rating, low carbon and low temps allow for an engine to really crank out the power. ESPECIALLY boosted engines.
 
Joined
Sep 11, 2021
Messages
234
In what world is 326hp “considerably less” than 320hp? Or is 348 ft/lb “considerably less” than 335?

While it can vary based on platform (I don’t run E85 in my Focus for example), the 5.3 from GM takes advantage of the very high octane rating of E85 and makes more power with it. Power is the most common reason people use E85. While there’s less energy in a quantity of E85 than a quantity of gasoline (hence the poorer fuel economy), the high octane rating, low carbon and low temps allow for an engine to really crank out the power. ESPECIALLY boosted engines.
What compression ratio we talking about? Where you get those numbers above? E85 should have enough octane to run 15:1. Anything else is wasted octane and lower energy content.
 

Circuit Rider

Thread starter
Joined
Sep 19, 2021
Messages
25
What compression ratio we talking about? Where you get those numbers above? E85 should have enough octane to run 15:1. Anything else is wasted octane and lower energy content.
9.6:1. Those are GM’s advertised numbers for the 5.3 on E85 vs regular gasoline.

There’s more than just compression ratio that affects a modern engines performance. In the 5.3, it’s a combination of the variable valve timing and ignition timing. A sensor detects the alcohol content of the fuel and advances timing which helps it make more power.

Engines have advanced a LOT since the 1960’s. These days, compression ratios are virtually meaningless. My Ford Focus runs at 12.5:1 and runs just fine on 87 octane fuel. That would’ve been unheard of decades ago. (And, ironically, really sucks with E85 despite a higher compression ratio. It does lose power.)

Edmunds did a comparison of the 3rd Gen Tahoe and found a 0-60 time of 9.8 with gasoline and 9.3 with E-85. Neither are exactly… er… fast. But it definitely demonstrates that the 5.3 really does take advantage of the properties of E85.

I did 1,500 miles with gas and 1,500 miles with E85. Kept track of everything and found the cost per mile was virtually the same (25% poorer fuel economy and 25% lower price per gallon, so that certainly makes sense). So the advantages seem worth it. The only real downside is the limited range. I get around 300 miles to a tank before the light comes on, compared to about 360 per tank with gasoline.
 
Joined
Sep 11, 2021
Messages
234
Two final questions. E85 is nada available where I am. What it cost compared to regular unleaded? And can you send a link showing where GM claims higher power with E85.
 

Circuit Rider

Thread starter
Joined
Sep 19, 2021
Messages
25
Two final questions. E85 is nada available where I am. What it cost compared to regular unleaded? And can you send a link showing where GM claims higher power with E85.

I got gas today and E85 was $2.29 and 87 was $2.86. It varies though. Sometimes the prices are closer and sometimes they’re further apart. I use an app called “Road Trip” which keeps track of cost per mile, and right now I’m averaging right around 21 cents per mile regardless of which fuel I use. Edmunds’ piece found that they spent more on E85 than they did on gasoline to go the same distance, so it can certainly vary.

Take a look under “specifications”:


It’s not uncommon at all for flex fuel engines to perform better under E85. Plenty of examples that are to the contrary though, it varies by vehicle.

At the end of the day, it’s gas with an octane rating of 105. Engines with forced induction and engines that can really take advantage of aggressive adjustable timing can really see a benefit.

There’s a whole subset of people who modify flex fuel engines because they can take a LOT of boost. E98, which isn’t really available on the street, is used in a lot of dragsters (and used by NASCAR).
 
Joined
Sep 11, 2021
Messages
234
2014 Tahoe with 9.6:1 compression when new. Yep, peak performance with regular unleaded gasoline. Cannot even tell us what he pays for his glorious E85 fill up fuel?:eek:
 

ZeeOSix

$100 site donor 2022
Joined
Jul 22, 2010
Messages
29,618
Location
PNW
If the pressure is measured after the filter (which it usually is), if the pressure drop across the media is significant, you will see it on the gauge.
Only if the pump is in relief. If the flow volume doesn't change, then the pressure won't change if the oil temp/viscosity is constant.

If the oil pressure sensor was before the filter, then you would see the pressure increase if the filter was clogging and the pump wasn't in relief.
 

ZeeOSix

$100 site donor 2022
Joined
Jul 22, 2010
Messages
29,618
Location
PNW
It's most likely some permanent shearing of the VM/VII additives. As they get chopped up, especially under high load, they're less effective at slowing the decrease in viscosity with increasing temps. Lower viscosity with give lower oil pressure.
That coincides with the draining of a quart and adding a new quart of oil.
 

ZeeOSix

$100 site donor 2022
Joined
Jul 22, 2010
Messages
29,618
Location
PNW
We have a winner!

I pulled out of the garage with 21 psi cold. Swapped the filter. Had 38 psi at idle pulling back into the garage.

Another EA15K50 is what I had on hand so I’ll order a wix and do a full oil change when I hit the 5k mark on the oil.

Fascinating! Thanks everyone!

I would’ve just changed the oil and wouldn’t have even CONSIDERED that the filter (which incidentally would’ve been changed as part of the oil change) was the culprit. I’m really glad I asked.
Does this engine have a variable flow oil pump? Filter must have been clogged enough to put the pump into relief, which would reduce oil flow and therefore oil pressure at the sensor.
 
Last edited:

ZeeOSix

$100 site donor 2022
Joined
Jul 22, 2010
Messages
29,618
Location
PNW
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.
Did you notice what the oil pressure readings were at full hot idle and higher RPM when you first got the truck before your first oil change? Just curious.
 

Circuit Rider

Thread starter
Joined
Sep 19, 2021
Messages
25
2014 Tahoe with 9.6:1 compression when new. Yep, peak performance with regular unleaded gasoline. Cannot even tell us what he pays for his glorious E85 fill up fuel?:eek:
Huh? I answered your question in my last reply with what I paid.

And, no, peak performance isn’t with 87. Compression ratio hasn’t been the end-all be-all for 40 years. 105 octane fuel allows for the ignition to advance far more giving additional power.
 

Circuit Rider

Thread starter
Joined
Sep 19, 2021
Messages
25
Did you notice what the oil pressure readings were at full hot idle and higher RPM when you first got the truck before your first oil change? Just curious.
Yeah roughly what they are now since the filter was changed.
 
Joined
Feb 27, 2009
Messages
6,488
Location
down in the park
What would the oil filter have to with the pressure drop?

Oil pressure is measured after the oil filter, so any pressure loss across the media shows on the gauge. Some big equipment I worked on uses oil pressure to determine when the oil filter needs changing, there's no interval.
 
Joined
Jan 3, 2020
Messages
596
Location
Brittany, France
All the gas cars i've owned over the years were converted to run E85 and it's not unusual to feel a very little bump in torque at mid RPM. Maybe because ethanol contains more oxygen than gas, it acts like a slight increase in displacement, don't know.
 
Joined
Feb 27, 2009
Messages
6,488
Location
down in the park
Nothing wrong with using the EaO, it's an excellent filter, the problem is your engine appears (please confirm with a filter tear-down) to be filling the filter with particulate, likely due to cleaning.

I'd probably use a less expensive filter changed more frequently if the filter dissection confirms my suspicions. You can step back up to the EaO once the loading starts to taper off. AMSOIL advises not using the EaO in these applications (and the HEMI) due to loading issues over extended drains. The filters are extremely efficient and these engines produce enough contamination apparently to be an issue when trying to run the filter that long.

I look forward to your filter C&P pictures!

Or keep using the oil pressure to do filter changes as needed, independant of oil changes...
 
Top