Excessive Oil consumption, 1995 Bonneville Vin K 3.8

Usually caused by a leaking intake manifold gasket

Dear Sir,
Here is the oil leaking Problem Identifying Technique

Engine oil leaks from the valve cover gasket are common.

The intake manifold plenum gasket may leak and cause increased oil consumption/burning and a spark knock during acceleration; the gasket should be replaced.

External oil leaks from valve cover gaskets, intake gaskets (front or rear), and the rear crankshaft (rear main) seal area are common. The rear main seal is an unlikely source. Normally, the bearing cap mating surfaces (as well as the sealing surface between the oil pan and bearing cap) are the source for the leaks.

Engine oil leaks at the distributor can be misdiagnosed as leaks from theintake manifold seal, oil pan gasket, or rear crankshaft (rear main) seal. A revised distributor is available if oil is found inside the distributor.

If the oil filter casing shows signs of distortion from excessive oil pressure, theoil pump should be replaced.

Often misdiagnosed as a leaking oil filter gasket, the oil filter adapter can seep from between the adapter and engine block.

Carbon buildup on the top of the piston is common. As the buildup increases with mileage and over time, symptoms may vary from light ticking, to ticking/hammering, to hammering/knocking noises. Fuel injector cleaner often solves the problem.

I think it helps to analyse u r Problem

if no puddles or no keaks you can see, then its probably your head gaskets, or the intake gaskets leaking. look all around intake to see if you see any leaks. if you do its your intake gaskets. how does the coolant look! on my car when the intake gasket was leaking, it made the coolant look milky and a chocolate type mixture. so check it out first, the intake gasket. Coolant may flow through the gasket to the inside of the engine and mix with the oil. Pull the oil dipstick out and look at it. Oil mixed with coolant will have a thick consistency. Examine the oil filter cap for any rusty-looking residue. good-luck.

The PCV valve does not control the oil situation, it just keeps the pans and valve covers from blowing off during a backfire. Excessive Oil in the breather is a result of excessive crankcase pressures, usually due to a worn engine, specifically rings.
SOME oil is normal, especially if you are loaded heavily and hard on the throttle.
There is a tester that measures crankcase pressures, but usually some other manifestation shows, like excessive oil consumption.

the PCV system draws crankcase fumes into the intake at idle and lower throttle situations. air going into the crankcase is filtered by the small PCV filter, where the oil shows up....

At highter throttle and lower intake manifold pressures, the system reverses, the PCV valve closes, and the fumes exit the crankcase VIA the breather filter. All of this is normal.

It costs tons less to periodically clean or replace the PCV filter.

excessive oil consumption and smoking is usually due to worn rings and/or valve guides in the engine. If you observe blue smoke coming out of the tailpipe, it signals a worn out engine.

If no external leaks, that's what it is. Maybe try to change the oil with a high mileage oil when changing the oil and filter.

I'm afraid, that these conditions don't get better with time.

A replacement motor, or overhaul of the present one is recommended if you cannot pass emissions tests in your area if required by law.

According to GM 1 quart per 1,500 miles is an acceptable oil consumption tolerance. 1 quart in 3k isn't bad.

I've had several gm 3.1 and 3.4 liters that have had there oil consumption issues remedied after the lower intake gaskets where replaced due to coolant leaking.

There are a couple of common problems that can cause oil consumption. Valve seals, bad rings, and PCV valves.

Valves seals would require a valve job which would requirethe removal of the heads. Rings would require a motor rebuild. Both of these are expensive options and oil is still pretty cheap.

Replacing the PCV valve might help. On the 3.8 it will be under the MAP sensor on the passenger side of the intake plenum.

As for as the intake gaskets, its a possibility but I don't have any hard evidence this could be the problem on a 3.8. Eventually the gaskets will start to leak oil. If you decide to replace them at that point I guess you will find out. I wouldn't do it on a hunch, its not a cheap repair.

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May have gotten the intake manifold gasket wrong/ backwards

Anything over 1 quart in 1000 miles might be considered excessive. It probably is not gaskets unless there is a leak. If there is a leak there might be a puddle of oil on the ground where you park it. If there is a puddle or drips of oil look at valve cover gaskets, oil pan gaskets, crankshaft seals , etc.

It could be burning and you don't notice. Remove air filter box assembly from top of intake manifold. Hold throttle wide open (engine off) and look through throttle body (flashlight may be required) and see if oil is puddled up inside manifold. If so then the intake manifold will need to be removed so the lower pan gasket can be replaced.