The Case of the disappearing Oil

I have a 99 Silhouette with the 3.8L V6. About 2 1/2 months ago, I had to start adding oil. Approximately one quart every three weeks. There are ZERO symptoms. It idles and accelerates well. The plugs are not fouled. The compression is 175 psi, near perfect. There are no drips, there is no spray on the underbody. There is no smoke. There is no excessive carbon in the tailpipe. Where is the oil going?

Don't know and would like too. My 2001 OLDS Silouette is using a lot of oil too. Would like to have a clue before I talk to a mechanic.

One possibility is the oil is entering the coolant. GM V6 engines have a high failure rate for intake manifold gaskets. This would make the orange Dexcool appear milky. We had the gasket replaced under warranty two years after buying our van.

99 with 3.8L ??

Valve stem seals?
A quart every 3 weeks is possible depending on your driving mileage. The oil gets by the valve end seals, then by the vlave guides into the combustion chamber where it's burned.
How many miles do you have on the engine. I have about 160K and recently had to replace a head gasket, the valves were leaking as were the valve seals, did a valve job and all is well.
Try a heaver weight oil and see if it helps.
Good luck
Let us know what happens.
94

One possibility is the oil is entering the coolant. GM V6 engines have a high failure rate for intake manifold gaskets. This would make the orange Dexcool appear milky. We had the gasket replaced under warranty two years after buying our van.Nearly impossible with the intake manifold gasket. The areas where the intake manifold seal preventing oil from entering the coolant (or vice versa) are not under direct oil pressure. Oil only has the opportunity to spray and splash around. Since it's not under direct pressure, it is very unlikely that oil would enter the coolant this way. It is far more likely that the coolant, which is under direct pressure, to enter the main engine cavity and mix with the oil.

Valve stem seals?
A quart every 3 weeks is possible depending on your driving mileage. The oil gets by the valve end seals, then by the vlave guides into the combustion chamber where it's burned.
How many miles do you have on the engine. I have about 160K and recently had to replace a head gasket, the valves were leaking as were the valve seals, did a valve job and all is well.
Try a heaver weight oil and see if it helps.
Good luck
Let us know what happens.
94


jimmy is right i had the same problem with a 2001 silo that i have and the oil was gettin by the valve seals the dealer put a new motor in for me told me it was shot if i were u sell the piece of crap ive put a new motor and trannyin mine and it only has 134 kms the vans are junk

Nearly impossible with the intake manifold gasket. The areas where the intake manifold seal preventing oil from entering the coolant (or vice versa) are not under direct oil pressure. Oil only has the opportunity to spray and splash around. Since it's not under direct pressure, it is very unlikely that oil would enter the coolant this way. It is far more likely that the coolant, which is under direct pressure, to enter the main engine cavity and mix with the oil.

You're so right CDRU. My son just found the reason that all of the oil in his 2002 Silo entered the cooling system. The oil filter is mounted on a circular oil cooler and the water jacket gave out internally - no leaks visible. The oil pressure, which is higher, then forced the oil into the cooling system. His local dealer wanted $215 for a new cooler but he got it on line from a Chevy dealer for $124. It pays to shop around. That same Chevy dealer saved me $140 when I bought new fog lights for my '99 Silo.

You're so right CDRU. My son just found the reason that all of the oil in his 2002 Silo entered the cooling system. The oil filter is mounted on a circular oil cooler and the water jacket gave out internally - no leaks visible. The oil pressure, which is higher, then forced the oil into the cooling system. His local dealer wanted $215 for a new cooler but he got it on line from a Chevy dealer for $124. It pays to shop around. That same Chevy dealer saved me $140 when I bought new fog lights for my '99 Silo.

What dealership was this that saved you so much money on your fog lights?? I'm interested because my '98 needs new ones too.

What dealership was this that saved you so much money on your fog lights?? I'm interested because my '98 needs new ones too.

That was P&G Chevrolet in Slovan, PA. HTTPS://WWW.Partszoneonline.com e-mail [email protected] . He charged me $71.06 per lamp + S&H. My local Olds dealer wanted over $140 for one and the list price is $102.98.

I just got a new fuel level sending unit from P&G for $86.40 + S&H - list is $150.26. Bill is very pleasant person to deal with.

Al