1999 GMC Sonoma Uses Oil

oil

#1

My 1999 Sonoma, manual 2.2 liter 4 cyl with 130,000 miles, uses (or loses) up to a quart of oil in two weeks. The oil pressure maintains a steady 60 PSI and the exhaust is clear, even when starting. That would seem to indicate that ring wear is not the problem. I put a big piece of cardboard under the truck over the weekend, no drips. The oil pan is dry, and I see no sign of leaks. After doing a number of googles, I read suggestions about replacing the valve guide seals (seems like major surgery) and switching from 5W-30 to 10W-40 or 20W-30. The truck is driven 300-400 miles a week on the Interstate in a moderate climate (Seattle area). Any suggestions?

Many thanks!


#2

Oil pressure would have nothing to do with oil consumption past the rings or valve seals. There may be little or no smoke because the converter is catching it.

After checking the PCV valve, the first step should be a dry and wet compression test and/or a leakdown test.
There is no test for valve seals and odds are the problem is related to the oil control rings, or wiper rings as they’re referred to.

If related to wiper rings even a compression or leakdown test may not be 100% accurate.


#3

The engine is burning the oil. The reason there’s no smoke out the tail pipe is because the oil isn’t burning at a fast enough rate the overwhelm the catalytic converter.

Did you know that some vehicle manufacturers consider a quart of oil burning per 1000 miles is normal for their brand new vehicles?

Tester


#4

With a vehicle that age, I would just add oil as needed. Years ago this level of consumption was considered normal.

Just make sure the PCV system is operational.


#5

On a truck this age, I agree with Doc.
Know that burning oil does not kill an engine. Running out of oil does. As long as you keep the level up you’ll probably keep putting down the road for some years to come. But start saving for a replacement.


#6

My 2000 Blazer started using oil after it hit 100k miles, but it was 1qt/3000 miles. Have you checked/replaced the PCV valve. A bad PCV in my 1993 cause a big increase in oil usage until it was replaced.

Ed B.


#7

1qt/2 weeks might do the cat in over time


#8

You don’t look at oil used/time, you look at oil used/miles.

1qt/600-800 miles? I wouldn’t worry about the cat.

Tester


#9

Actually, I consider 1qt/600 miles to be pretty high oil consumption

This is not a car from the 1940s that gulped as much oil as gasoline

I stand by what I said . . . I think it’s possible the cat will suffer from this oil consumption


#10

A quart per 600 miles is horrible in my opinion. Like all of my other cars, this high oil consumption issue being considered as “normal” kind of baffles me a bit and the only place for that burnt, and unburnt, oil to go is onto the leading edge of the converter substrate.

Knock the guts out of a converter removed from an oil burner and see how much of that honeycomb is plugged up.


#11

A quart per 1000 miles sucks in my opinion no matter if it’s referred to as normal or not.


#12

I had a 1986 Tempo that burned oil at 800 mi/qt from new until traded at 130K. I just changed the oil filter every 5K and kept throwing dino oil in and never had an engine problem (other than the thirst for oil).


#13

If it were my truck I would replace the valve seals, unless you don’t plan to keep the truck long.

I am used to a quart every 1500 miles but a quart of oil every 600-800 miles is too much for me. For a push rod engine this should be an easy task, perhaps three hours of labor.

I have had to remove engines on Toyota products to remove all four cam shafts to replace the valve seals (under warranty) and an S10/Sonoma repair just sounds like fun.


#14

A 99 GM with 130,000 miles on it using oil?

I’m shocked!

Tester


#15

All that oil will also reduce the cat efficiency, perhaps to the point that you are failing the smog


#16

Deposits can also build up on the leading edge of the substrate in the converter and decrease engine performance along with fuel mileage to varying degrees; depending upon how much of that honeycomb is clogged.

Sometimes that engine thought to be running well and at its optimum is not quite as optimal as it should be.

That aside, if this is all about clean air then how is dumping countless millions of quarts of oil into the atmosphere on a daily basis helping at all… :frowning:


#17

@Blacksmith, if you experiment with heavier viscosity oils I would be interested in your results. But keep us posted whatever you try.


#18

Check the deposits on the inside of the tailpipe (when cold) with a tissue if you don’t want to soil your finger.
Lots of black and oily? If so it’s burning oil.
+1 to first checking the PCV system (valve, hoses and vacuum port).
My 2006 Matrix has the cleanest running engine I’ve ever had or seen.
The inside of the pipe is still bright stainless with a few rusty streaks.


#19

Many thanks to all for your comments, I am gratified for the quick response.
I’ve learned that GMC/Chevy eliminated the PCV valve in the 2.2 engine from 1998 forward.
I did the cold tailpipe test just now, considerable quantity of black soot. I will start reading up on replacing the valve seals. I’m well set up with tools, but I wish I was doing the job on my old Chevy inline 6.
Anyone know offhand what the compression on the 2.2 engine should be?
I replaced the cat converter a couple months back and still have the old one, perhaps would be interesting to cut the intake end off and look for oil residue, unless there are toxic substances inside.


#20

“I replaced the cat converter a couple months back”

Why did you replace the cat?