Oil Consumption--Switch to high mileage oil?

[Silver 99 Camaro]

I noticed over the last year my car using more oil than in the past. I use the oil change light for oil change intervals, and it usually comes on about every 4500 miles. Before, the car would use about 1/2 quart during that time. Now, it uses no oil up until 2000 miles, 1/3 quart by 3000 miles, and 1 full quart by 4000 miles (I just added some). I use Castrol GTX and the larger PF52 oil filter...the car has 74,000 miles. Does that seem normal, or too high for that mileage?

My main question is, would high mileage oil, like Valvoline or Castrol, help at all? I've heard good things about those products from a lot of people but haven't tried it myself yet. Otherwise, I'll just add oil between changes, or ignore the light and change my oil every 3-4000 miles before it uses all that oil.

[terminaldegree]

Re: Oil Consumption--Switch to high mileage oil?

First off, I'd change the pcv valve. It's cheap and eliminates that possibility.

Personally, I'd leave it all alone and just change every 3,000 with conventional oil.

If your car isn't leaking oil, just go one grade thicker and see if it helps [10w40 instead of 10w30] consumption. This is more economical than the "high mileage" oils.

If you are leaking, then sure, give the HM oil a shot in the same grade you're running now. Don't expect any miracles.

My car uses about half a quart in 5,000 miles max. Any more than that and it would bother me.

[Silver 99 Camaro]

Re: Oil Consumption--Switch to high mileage oil?

I changed the PCV valve at 55,000 miles...I could do it again. It does not leak at all, at least not on the pavement. The rear main seal is a little moist (seepage) as well as the valve cover gaskets. But that is all really minor seapage as far as I can tell. There is no smoke out of the tail pipe either. The GM spec by the way is that up to 1 quart per 1000 miles is acceptable before they think anything is wrong with it. Crazy...

[terminaldegree]

Re: Oil Consumption--Switch to high mileage oil?

Seeing as the PCV costs all of $2, I'd throw another one in. When it malfunctions, it can cause oil consumption.

[Silver 99 Camaro]

Re: Oil Consumption--Switch to high mileage oil?

Since it hardly uses any oil until after 3000 miles it's probably not the PCV valve or a problem with the rings. It would burn it all the time if that were true. Oil burns off easier as it breaks down. So the easy solution is to change it more often. Still, I like using the oil life monitor since it's supposedly really good, so does anyone have any experiences positive or negative with high mileage oil? It should be more resistant to oil burn off.

[bah]

Re: Oil Consumption--Switch to high mileage oil?

where is this PCV valve and what does it do, something that i can change myself, idk what the previous owner has done so i figure if its a $2 part it wouldnt hurt to change it myself

[terminaldegree]

Re: Oil Consumption--Switch to high mileage oil?

On the 3800, it's the little black cover on top of the intake manifold [right on top of the engine]. Remove the two screws and the pcv valve pops out. Careful not to lose the spring or the o-ring, as you reuse them.

The pcv valve is one of those silly pollution control devices. I think it burns oil vapors instead of letting them out into the atmosphere. When they malfunction, you can sometimes end up burning oil, having a lousy idle, or notice a drop in your mpg. It's the first thing I replace when any of those things starts to happen.

[CDNFB]

Re: Oil Consumption--Switch to high mileage oil?

The Positive Crankcase Ventilation system is designed to route crankcase gasses (produced by blowby and off gassing of lubricants and chemicals) into the engine intake system where they are introduced into the cylinders to be burned off.

The Positive Crankcase Ventilation (PCV) Valve,s function is to isolate pressures that can be higher in the engine intake from the crankcase. In other words, when you go from idle to Wide Open Throttle (WOT) the resulting intake pressure rise (to atmospheric) does not transfer into the crankcase. When the pressure in the crankcase rises to a pressure higher than that in the intake, the PCV vavle opens allowing the crankcase gases to enter the intake system then into the cylinders to be burned off.

In many engines the PCV valve is not a straight check valve (as in full flow one way and no flow the other way) but rather a restrictor check valve (full flow one way, restricted flow in the opposite direction).

Excessive pressures in the crackcase can cause loss of power 2 ways:
1) The pressure is exerted on the backside of the pistons meaning every time the piston moves down the cylinder it has to work against the pressure.
2) The pressure forces crankcase gases past the rings of the piston on the downward intake stock and enters the cylinder (it also carries oil from the piston/cylinder wall with it, thus increased oil consumption) thus reducing the amount of intake air the cylinder is trying to draw in. Because of reduced volumetric efficiency, there is less intake airflow, and less airflow means less fuel, which means less power.

Excessive crankcase pressures can also cause oil leaks and blown out gaskets, seals and dipsticks.

Wow, got carried away with that one didn't I!:rolleyes:

DZ