Oil Sample low Viscosity

[Mango]

Hey All
My 89 burb 350 197898 miles oil samples coming back with lower and lower oil viscosity?
No coolant, fuel in oil sample?
New intake manifold Gaskets about 5600 miles ago
Burns oil only at start up valve seals
Could it be O2 sensor does seem to run rich $
How to check O2 sensor it is the original

Thanks

 

[Ricko1966]

Hey All
My 89 burb 350 197898 miles oil samples coming back with lower and lower oil viscosity?
No coolant, fuel in oil sample?
New intake manifold Gaskets about 5600 miles ago
Burns oil only at start up valve seals
Could it be O2 sensor does seem to run rich $
How to check O2 sensor it is the original

Thanks

I hate to just replace O2 sensors without testing them. But 35+ year O2 sensor,just get new one. While your old one is out put a volt meter on it heat it with a propane torch.watch your meter, voltage should be between .1-.9 volt and vary with heat. Another thing you could do is get the O2 hot,drive around a while. Disconnect the O2 sensor,put a meter on it,let the voltage get stable. Now create a vacuum leak,watch your meter. Spray carb cleaner in the intake,watch your meter. Let things stabilize. It should read .1 full lean .9 full rich .5 just right.

 

[fast 99]

200k is a lot of miles. Could just be leaking by the rings. Perform a leak down.

 

[Mango]

New o2 sensor runs better and mileage is up slightly
A mechanic suggested to check injectors after turning the engine off and see if they are still pushing out fuel
Is this a thing?

 

[Ricko1966]

New o2 sensor runs better and mileage is up slightly
A mechanic suggested to check injectors after turning the engine off and see if they are still pushing out fuel
Is this a thing?

Absolutely,with time injectors can develop leaks just like your kitchen faucet. Turn them off but they still leak a little,sometimes a lot. You should also check your spray pattern.

 

[Sad Sack]

Hey All
My 89 burb 350 197898 miles oil samples coming back with lower and lower oil viscosity?
No coolant, fuel in oil sample?
New intake manifold Gaskets about 5600 miles ago
Burns oil only at start up valve seals
Could it be O2 sensor does seem to run rich $
How to check O2 sensor it is the original

Thanks

Just curious, so if ya pull the oil dipstick out and sniff it on the end, do you smell gas?

 

[gmbellew]

New o2 sensor runs better and mileage is up slightly
A mechanic suggested to check injectors after turning the engine off and see if they are still pushing out fuel
Is this a thing?

easiest way to check for leaky injectors is sometime on a cold engine put some paper towels under them, turn key to ON for 3 sec to let the fuel pump prime, key back to OFF. then check the paper towels for fuel.

 

[Mango]

Hello
Oil does not smell like Gas the guys in the shop could not smell gas!

 

[cadillac_al]

Is this quality oil or economy oil?

 

[Mango]

NAPA 10W-30 made by Valvoline

 

[Mango]

@cadillac_al
Should I do better?

 

[cadillac_al]

I tried some Carquest oil in my Cadillac Deville. It was on sale. The oil light came on at idle on like the 2nd day. I ran it for a week or so and then I drained it and put some name brand oil in it and the oil light didn't come on. I don't really trust the parts store brands. Your low viscosity is probably as simple as that.

 

[Grit dog]

How do you know the viscosity is lower than it should be? What are the actual vs specified values at how many miles/engine hours.
You’ve given no frame of reference.
What was the symptom that prompted you to do an oil sample. That’s an unusual test on a 200k mile 35 year old run of the mill motor.
Old motor runs good, no issues? I’d throw some thicker oil at it if you think the oil pressure is low or the oil is thin….

 

[bucket]

I tried some Carquest oil in my Cadillac Deville. It was on sale. The oil light came on at idle on like the 2nd day. I ran it for a week or so and then I drained it and put some name brand oil in it and the oil light didn't come on. I don't really trust the parts store brands. Your low viscosity is probably as simple as that.

Sounds like your Deville has very borderline OK oil pressure.

 

[cadillac_al]

Sounds like your Deville has very borderline OK oil pressure.

Probably so, it didn't like cheap oil. That was the only time the oil light came on when I owned it.