Where could the oil be going?

[gavinl]

I'm looking at a 97 Mercury Cougar 4.6 SOHC V8. Owner says the engine consumes about a qt every 2000miles.

The car's 150miles away and the local mech found no leaks, no smoke or any obvious signs of oil leaks in places like the valve cover, head gasket or rear main seal.

My Q is where could the oil be going??

 

[kreigle]

If you can rule out the possibility of leaks, then it is probably burning it.

My car burns 1qt every 500-600 miles and shows no obvious smoke in the rear-view when I drive (except for extended periods of idling). Even the plugs look normal with no excessive soot or oil residue.

 

[robbobster]

Check the PCV lines. These Ford modular engines are known to suck a bit up via the PCV system. Perfectly normal. I'd consider that much consumption slightly on the high side, but certainly not a deal breaker.

I've consistently burned about a half-quart over 3K miles on my Expedition since it was new, this is about average for many mod motors. But some folks note almost no oil consumption, so it varies a bit.

 

[gavinl]

Thanks guys, now I can put my mind to rest and arrange to see the cougar. It's a sweet looking car with no rust (for a midwest car!) and a Sport package.

Can the PCV system be improved by rigging a oil catch can in series?

 

[fuel tanker man]

If you get the car you may want to do an Auto RX treatment, or at least do a couple of quick OCI's with Delo or equivalent HDEO.

I believe I cured my old Ford Escort from buring oil by running some Delo through it last summer. Prior to the 2K mile Delo run, the car would use a quart of oil every 800 to 1000 miles.

After the Delo apparently cleaned her up a bit, the car is back to using no oil between 3K changes. It is commonly believed that sludge caked in and around the piston rings prevents a good seal, and results in oil getting past them. If you can clean up the sludgy rings, you may improve things at least some...

If you're wondering about whether an engine is burning some oil, take the car out on the highway at night and gas on it when another vehicle comes up behind you. If there is oil being burned (or raw gas shooting out the pipes) you'll see the fog much more easily in the glare of the headlights behind you.

For what it's worth...

Dan

 

[robbobster]

quote:

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Originally posted by gavinl:
Can the PCV system be improved by rigging a oil catch can in series?

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Not really. Most forced-induction guys have a problem with this and nothing seems to work all that well for them. My guess is that you may reduce it but you likely won't eliminate it.

There are lots of catch cans and such available but I wouldn't worry too much about it.

Just make sure that's where the oil is going, and not out the tailpipe or leaking out somewhere.

 

[gavinl]

Ok! Time to stock up Auto-RX once I get the Cougar.

 

[Fuelrod]

If your 4.6L Ford only burns one quart in 2000 miles, be happy! It probably really burns a quart every 1000 miles, but be happy anyway because most of them do that. A little "Top Oil" doesn't hurt a thing!

 

[mechtech]

Who knows what weight oil, or driving conditions, this car sees. A lot of urban driving has the engine running, but no miles accumulating.
Anyway, 1 qt. in 2,000 mi.for a 4.6L V8 is roughly comparable to an engine that is a 4 cyl. 1.8L and use a qt. every 5,000 or so.
Not so bad in that light.

 

[Mike_dup1]

fyi-The oil use may be attributed to the oil and not the engine. Read this, every oil functions differnenty in the engine. Look at the last line, that says its ok for 22% of the oil to burn off, about 1/4 of qt which probably = the 1qt/2000 miles in that car. All oils are not = in this spec. Many synthetics are very low while many dino oils reach the 22% and beyond.

quote:

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volatility - Volatility is a measurement of the amount of oil which is lost during engine operation because of burn-off.

There are several concerns associated with oil volatility. First, engine oil is lost and must be replaced. Additionally, the viscosity of the remaining oil increases. Moreover, oil loss could change the effectiveness of the oil as a lubricant. The chemical properties and additive package ratio of the oil may also change as the volatile components are burned off. Finally, there is also evidence that the volatilized oil may damage the exhaust catalyst as it passes through.


The volatility of an engine oil is measured using ASTM test method D5800. A known weight of oil is heated to 250°C in a special chamber and held at that temperature for one hour. Air is introduced into the chamber and maintained at a constant flow rate under slight vacuum. After one hour, the amount of oil remaining in the chamber is weighed again. The percentage of oil lost is determined by comparing the remaining weight of oil with the original weight of oil.

Specifications set by ILSAC determine that the amount of engine oil lost through volatilization at 250°C for one hour should not exceed 22%.

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[ March 13, 2005, 09:01 AM: Message edited by: Mike ]

 

[punisher]

The valve seals on 4.6s have a propensity for geting hard and letting excess oil into the chamber. Sometimes you will notice a blue puff on startup after the car sits at least 1/2 hour. The oil that does burn during driving doesn't really smoke a lot due to the action/heat of the cat converters. Seemed to be a bigger problem in hot climates(like trans converter shudders). Ford as well as aftermarket gasket/seal makers have released several valve seal upgrades over the years.

 

[1maniac]

quote:

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Can the PCV system be improved by rigging a oil catch can in series

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Somebody here had a post about PCV oil blowby getting sucked into the air filter. They also rigged up a small filter to stop this and it seemed to work well.

 

[Fuelrod]

There already is an oil trap in the valve cover, the PCV is located in a pretty dry area. A little oil consumption is a GOOD thing, not a BAD thing. That top compression ring will last a lot longer if it sees a little oil!

 

[Huhwhye]

It's oil vapor that makes it's way through PCV and breather systems. Oil vapor has no problem making its way around valve cover baffles being pushed by crankcase pressures.

It's such a small amount of oil I doubt it has any effect on anything, lubrication or smoking, whatever. Divide 1 quart by 8 cyl x how many thounsands of revolutions of the motor in 2000 miles of driving. I bet you can't even measure how much oil is burned by 1 cylinder each time it fires. That oil will have no effect on the anything. If that's what is causing the consumption I woulded worry about it.

 

[Huhwhye]

Sorry for the double post