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Discussion Starter #1
Today I switched my 2007 Classic (15K miles) over to Amsoil 15-40 and Wix filter. I immediately noticed a drop in pressure. Before the Amsoil at 1500 RPM the pressure was just barely under the 60 mark, now it is down 2 ticks. also now below 30 at idle. Anybody else experience this?
 

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I have seen a little bit of a drop like you are describing with delvac 1. From the way I have heard it explained....the oil pump on the duramax is a high volume pump, so there is less resistance with the new oil. As long as you don't have the low oil light on, I wouldn't worry about it too much. Your truck is still under warranty, you can talk to the dealer and see if they have any ideas, but mine is the same way.
 

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This common and expected, and also nothing to worry about. The oil actually pumps easier. This is where the mpg rise (I know it's pretty small) comes from, less parasitic (pumping)losses. I have seen this in every application across the board, cars, trucks, boats etc.
 

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Yeah, normal. They way it works is that your pump moves, lets say 20gpm. To move 20gpm, dino oil, with less flowablility, produces 60psi. Now, the oil flows easier, there is only 50 psi, but still 20gpm. Less resistance to flow. Follow?
 

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Discussion Starter #5
thanks guys for the info. i have switched a couple earlier vehicles over to full syn in the past and did not see the pressure drop. i understand the rationale and quit worrying about it. FYI, I experienced an immediate 1.3MPG increase with AMSOIL. at 3.20/gal that is significant!
 

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gotta love amsoil

thats what I noticed to with amsoil been using it for over 100k now and no problems. As a matter of fact I use there syn trans fluid and there syn diff fluid in my van and I can see the increase of fuel mileage. engine and trans also run cooler. :D:D
 
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