| Re: [GMCnet] Tid Bits: Oil consumption. It's all in how/where it's consumed. [message #336531 is a reply to message #336528] |
Thu, 30 August 2018 08:58   |
Richard Denney
Messages: 920
Registered: April 2010
Karma:
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Senior Member |
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On my old engine, I was getting about 15 psi at idle, and 30 or so at
speed. The engine had an uncertain history (valve covers were painted
black) and 90k+ miles, and I switched to Mobil1 High Mileage 15W-50.
Pressure was 20 at idle and 35-40 at speed after that. Which is plenty. But
I didn’t make that change to get higher pressure, I did it to get a
stronger oil film in looser bearings.
Dick P once said that NASCAR racers can run all day at 30 psi and 8000
RPMs. Pressure is not what we need—an ever-present film is what we need.
The problem with worn tolerances is not so much that they relieve pressure,
but that they leak a lot of oil. A high-volume pump prevents those leaks
from causing starvation somewhere else.
Do we need it? Certainly not for a tight engine. But I don’t worship at the
altar of GM engineering, either. They did as much cost engineering,
fuel-consumption engineering, and emissions engineering as they did
durability engineering. Their engines were tight not because they made the
parts fit (as we expect to do during a rebuild), but that they selected
parts with the right dimensions for the assembly task at hand. As I
understand it, parts were sorted across their manufacturing tolerance range
and the selected on the line as needed. They were auto workers, not
artists.
Rick “who uses a mechanical oil pressure gauge” Denney
On Thu, Aug 30, 2018 at 12:48 AM John Phillips
wrote:
> What does changing the oil weight do the oil pressure? I feel my oil
> pressure is low. Would like to have a real gauge. Coach has 117k miles. OP
> said it was reabuilt at 100k.
>
> --
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
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