Vortec 5.7l oil consumption.

[thegawd]

PCV valve ordered... haha cuz no I haven't checked it lately but it was fine in the passed. but its old and time for a new one.

Al

 

[jjester6000]

All that comes off the tail pipes on cold start is a smell of LPG (propane) as it goes rich before the O2 sensors are hot enough to rein it in.



Twice that on a motor that has done a fifth of that mileage definitely has something amiss.




Brand new a few months back.

Valve seals usually fail due to age, not mileage. My 89 K2500 had only 119k on it and only 30k on the motor yet it still had bad valve seals since they cracked with age (About every car I've ever owned has had bad valve seals)

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Valve seals are a very common issue on most old engines.

 

[jjester6000]

Valve seals usually fail due to age, not mileage. My 89 K2500 had only 119k on it and only 30k on the motor yet it still had bad valve seals since they cracked with age (About every car I've ever owned has had bad valve seals)

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Valve seals are a very common issue on most old engines.

Anyways I'm saying that bad valve seals are more likely on lower mileage engines since they sit around and the rubber dries up.

 

[Pinger]

Anyways I'm saying that bad valve seals are more likely on lower mileage engines since they sit around and the rubber dries up.

I hadn't thought of the valve seals before you mentioned them.
At an average mileage of 2000/year they may have dried up a bit. Wondering also if LPG offers them less protection?

 

[Schurkey]

Thousands of years ago, when I was a Service Advisor in a GM dealership, GMs official policy was that a quart to 800 was NOT bad enough to repair under warranty. I think they had to burn a quart to 700 for warranty coverage.

Of course this was crazy. Everyone knew it was crazy. People were ANGRY that they'd bought an oil-burning pig and GM wouldn't fix it...but a quart to 800 was, officially, "OK". NOW you know why they had to take the ZDDP out of the engine oil--at a quart to 800, they were poisoning the catalytic converter. If the major manufacturers had set realistic oil consumption limits, they could have kept the ZDDP. But that would have cost GM--Ford--Chrysler money. Better to screw the new-car customer with oil burning, and then screw the used-car customers by making the oil less able to handle high pressure of flat-tappets.

(Truth to be told, the bigger problem with failing cam/lifter sets was the soft metal of cheap Communist Chinese cams and lifters.)

Realistically, a quart in 2000 doesn't bother me much. My Trailblazer used to go 4000--5000 to a quart, but that's down a little now--perhaps a quart to 3000. 'Course, it does have a quarter-million miles on it.

 

[PlayingWithTBI]

Here's some pics showing evidence of detonation, fuel additives, tan staining from fuel facing intake valve, running in open loop/closed loop, and sucking oil throught the PCV valve. HTH.

https://www.dynamicefi.com/SparkPlug.php

 

[jjester6000]

I hadn't thought of the valve seals before you mentioned them.
At an average mileage of 2000/year they may have dried up a bit. Wondering also if LPG offers them less protection?

Yes LPG definitely offers less protection. I'd even go as far to say that you're valve guides might be a bit worn as well.

It's like not running a lead additive in an older engine that needs lead, but to a lesser extent. The gas does lubricate the guides a slight amount, and stops them from wearing (like leaded gas did before hardened valve seats/guides).

Whether it is the guides or seals I can't tell you, but it's probably a bit of both (Worst case, you're rebuilding the heads which is not a massive deal).

If I were you, I would put in a quart of lucas oil stabilizer in next oil change.

It will help rejuvenate the seal and probably significantly reduce consumption.

 

[Pinger]

Here's some pics showing evidence of detonation, fuel additives, tan staining from fuel facing intake valve, running in open loop/closed loop, and sucking oil throught the PCV valve. HTH.

https://www.dynamicefi.com/SparkPlug.php

Here's a photo of one bank's plugs. Not easy to make out the porcelain as the flash has bleached them to pure white but there was a tan longitudinal ridge similar but not quite as heavy as can be seen on the underside of the side electrodes.
I was expecting one or two heavily oiled plugs (compatible with ring or inlet manifold gasket failure) and saw the colouring I did as merely being from fuel.
I have an AFR gauge now and from a recent 100 miler plus short local runs it seems to be running very slightly rich Lambda = 0.88 to 0.99, an average of 0.94. It's probably done the last 400 miles on that mixture set-up.

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[Pinger]

Yes LPG definitely offers less protection. I'd even go as far to say that you're valve guides might be a bit worn as well.

It's like not running a lead additive in an older engine that needs lead, but to a lesser extent. The gas does lubricate the guides a slight amount, and stops them from wearing (like leaded gas did before hardened valve seats/guides).

Thing is I don't know the extent of LPG running it's done. Previous owners used gasoline a lot as there wan't an LPG pump nearby. I still think the bulk of its running (since 2002) was on LPG though so possibly there's top end wear.

Whether it is the guides or seals I can't tell you, but it's probably a bit of both (Worst case, you're rebuilding the heads which is not a massive deal).

But for the time it takes....

If I were you, I would put in a quart of lucas oil stabilizer in next oil change.

It will help rejuvenate the seal and probably significantly reduce consumption.

The oil I'm using is 'kind on seals and hoses' so there's some hope it may re-supple a hardened seal. (I've seen it happen with the same base oil in a water pump gearbox).

Don't suppose inlet backfires do much for valve seal longevity....

 

[Maurice Evans]

I'm seeing oil consumption higher than expected for a low mileage 1999 Vortec 5.7l running with 10W/30.
On another thread there's one poster who says changing to a xxW/40 cuts consumption - eventually ( a gradual process, why not immediate?).
Trying to figure if I have an internal problem or is this just what these engines do. I've pulled the plugs and the worst I'm seeing is a very light brown/tan on the porcelain of some of them (and only on one side of a plug).

So I'm throwing out the following questions to try and find out what's 'normal' for these engines.

A. What consumption do you have in miles/quart?
B. What grade of oil do you run?
C. What mileage has your engine covered?
D. What colour shows on your spark plugs?
TIA.

I have 180K on my 5.7 running 5w/30 and it does not use any oil. It does however have a rear main seal leak. I swithed from 10w/40 to 5w/30 because of an engine knock when cold.