| Re: [GMCnet] Tid Bits: Oil consumption. It's all in how/where it's consumed. [message #336505 is a reply to message #336504] |
Wed, 29 August 2018 13:22   |
James Hupy
Messages: 6806
Registered: May 2010
Karma:
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Senior Member |
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My 403 when I first got it, had 87,000+ miles on the clock. P.O. had been
using 10w - 30 dino oil in the engine. Consumption was 800 or so miles per
quart, which I thought was a bit high. My mechanical fuel pump gasket was
leaking a bit of oil, so I fixed that and cleaned up all the surplus stuff
on the outside of the block. Ran long enough to tell that oil consumption
didn't change much. Darn. So, I decided to change to Valvoline 20w - 50.
Oil consumption changed to a quart every 1200 to 1500 miles. That is where
it is today with over 125,000 miles on the engine. Compression is
consistent at 150 psi across the board. So, the old girl is going to be
driven like she is, until something changes dramatically. Factory says that
a qt per 500 miles is acceptable. I think that borders on excessive
consumption, while the factory is covering their butt on warranty claims.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Wed, Aug 29, 2018, 10:41 AM Bob Dunahugh wrote:
> Sully. Don't know when most of the oil consumption would occur. Never even
> saw a hint of oil smoke ever. Thought that the 50 might help some. It did.
> Bob Dunahugh
>
>
> ________________________________
> From: Bob Dunahugh
> Sent: Monday, August 27, 2018 9:53 PM
> To: gmclist@list.gmcnet.org
> Subject: Tid Bits: Oil consumption. It's all in how/where it's consumed.
>
>
> 6 years ago. I knew someone that got very upset that their engine
> consumed one qt every 300 miles. So we looked at the spark plugs. All the
> spark plugs showed about the same as to discoloration/deposits. The
> compression test came in at reasonable numbers. At 115 to 123 psi. Not
> great. But not bad. Inspection camera showed oil washing around the edges
> of the pistons. All washing on all pistons was about the same width. Again.
> Not a great sign. But not bad. Just expected. Put a dial indicating
> micromotor to the top of each rocker arm. Just looking for consistency
> between all the intake. Then all the exhaust. Looked good. But that test
> doesn't show how much the lifters are dished. Or how much of the cam lobes
> are gone. Again used the inspection camera to check the cam gear/chain. Had
> been changed at some past point. Warm oil pressures were13psi at idle.
> 21psi at speed. This is a candidate for a high volume oil pump. But the
> pump could over load the piston oil control rings. That are already over
> loaded. Thus it could up oil consumption. I suggested running it as is. And
> run a heavier oil. He's been using 20W50 oil. Still running well. Oil
> consumption has been at about 400 miles per qt. If the engine had all the
> oil consumption issues in just one or two cylinders. That's time for a
> rebuild. As for what's best for you. Not my monkeys. Not my circus. Bob
> Dunahugh
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