synthetic?

[20inchaurora]

been running synthetic in my car for the past 2 oil changes....about 50k on it now, been changing the oil every 3000. only using about 3/4 of a quart over the course of the 3000. anybody else using synthetic? and if so, are you experiencing similar oil loss? i've been told that oil loss is common on the 4.0s and 4.6s....my buddy with an 01 STS experiences the same thing

[mission008]

I haven't noticed the loss in mine yet but I too have heard about that oil loss in the 4.0's and 4.6's

[Aurora40]

Well, 3/4 of a quart over 3,000 miles, and you are changing the oil at 3,000 miles, means you don't ever have to add oil. I'd say that's quite normal for just about any car.

As an aside, I'd suggest using the oil life monitor. I bet at 3,000 miles the monitor may not even be down to 50%. It will save you money on oil, the time to change it, and of course it is better for the environment.

[kobalt]

I second that. Get your money's worth from synthetic and follow the oli life display.

[kobalt]

The oil consumption you are experiencing is quite normal and no cause for concern. Check out this link:

www.cadillacforums.com/cadillac-tech.html#noil

[20inchaurora]

aurora40, i check the oil fanatically, at least once a week. and i added about 3/4 over the 3000 miles. and as to saving the environment, at our shop we have a waste oil heater...burns used oil as clean as a new furnace burns heating oil i've always been a strong believer of changing the oil at 3k...any harm to letting the oil moniter tell me when? i know these auroras are smart...but are they that smart?

[mission008]

20inchaurora said:

i've always been a strong believer of changing the oil at 3k...any harm to letting the oil moniter tell me when? i know these auroras are smart...but are they that smart?

thats what i'm saying....i'm a little skeptical about changing the oil when it tells me to

[Aurora40]

From GM:

How often should engine oil be changed?

- 3,000 miles (5000 km)
- 5,000 miles (8000 km)
- 7,500 miles (12000 km)
- 10,000 miles (16000 km)

Actually, all of these are correct, depending on operating conditions. Oil life is affected by many factors other than just miles driven. The type of driving, temperature, and engine load all play a part.

That’s why GM has developed the GM Oil Life System, an electronic watchdog that keeps track of all these variables and notifies the driver when it’s time to change oil. (fig. 1) We first told you about the GM Oil Life System in the March 2000 TechLink. Since then, the system has become standard equipment on nearly all GM products.

Briefly, the Oil Life System is programmed with a certain number of engine revolutions. As the engine runs, this number is reduced until it reaches zero, and the Oil Life light or message comes on. But there’s more. Operating the engine under low or high temperatures, and under high load conditions subtracts (penalizes) extra revolutions, so the light comes on sooner.

Changing engine oil according to actual need rather than an inflexible schedule provides several benefits.

First is simpified determination about when to change oil. No more decisions about “normal” conditions vs. “severe” conditions. Second is reduced operating costs for GM’s customers, who now have to change oil only when it’s needed. Third is minimizing the amount of used oil that must be disposed of. And fourth, engines will always be running with sufficiently fresh oil, for long life.

These benefits will be realized only if engine oil is actually changed as indicated by the GM Oil Life System.

Some customers “get it” when it’s explained to them. Others may be reluctant to deviate from traditional oil change interval charts. So, part of the responsibility falls on retail service people to help get the message out.

TIP: To help you do this, an IDL broadcast is being prepared. Consult the GM Training Program Guide and Schedule for “Understanding the GM Oil Life System” (PPS03.P1D).

There’s More
Traditionally, the vehicle maintenance schedule has been based on miles or time, while the oil change interval is now based on the GM Oil Life System. This could result in customers having to bring their vehicles in for an oil change when the light comes on, only to find that the vehicle is due in a month for scheduled maintenance.

That’s all changing. In the accompanying article “Simplified Maintenance Schedules”, you’ll learn how maintenance intervals are now being tied into the oil change intervals indicated by the Oil Life System.

- Thanks to Jerry Garfield and Chuck Burns

[Aurora40]

and

Oil Life Monitor --
How Does It Know?
How long will oil last in an engine? What
reduces the oil’s effectiveness? When should
it be changed?
Lubrication engineers perform a number
of tests to answer these kinds of questions.
Vehicles are operated under prescribed conditions,
and periodically a sample of the oil is
taken into the laboratory for analysis. When
the condition of the oil is no longer satisfactory,
the mileage is noted.
From controlled testing like this, engineers
in the past have determined two sets
of mileage numbers, one number for normal
driving and the other for severe conditions.
Severe conditions can mean that the vehicle
is driven hot (for example, pulling a trailer up
a mountain) or is driven such that the oil
never warms completely (for example, trips
less than 5 or 10 miles in a winter climate). It
is then up to the owner to decide whether
their own driving is normal or severe and to
change the oil accordingly.
Now, science and technology have found
a way of taking the guesswork out of the picture.
GM is installing an oil life monitor in an
increasing number of new vehicles. Using a
simple indicator lamp or readout on the
instrument panel, this system notifies the driver
when to change the oil.
The February and March 2000 issues of
TechLinkexplain how to reset these monitors.
Here’s information on how an oil life
monitor works.
Additives
Straight oil is not an ideal lubricant in an
engine. A package of additives is needed to
give the oil properties it does not naturally
have or to enhance its natural properties.
Some of the tasks accomplished by additives:
- viscosity modifiers, to keep the oil the
proper thickness over a wide range of
operating temperatures
- anti-oxidant, to keep the oil from
thickening
- corrosion inhibitors, to protect
engine components
- anti-wear
- anti-foam
- detergents, to suspend solid particles.
What Makes Oil "Wear Out?"
If you were to start out with a crankcase
full of fresh, clean oil, and drove the vehicle
for a period of time, eventually the oil would
have to be changed. During this time, what
can change fresh oil into "worn out" oil?
First, dilution. When gasoline is burned in
the combustion chamber, the by-products
include a lot of water. Some of this water can
find its way into the crankcase through piston
ring blow-by. If the engine is cold, and if combustion
is not perfectly complete, a small
amount of acid is formed. It, too, can blow-by
into the oil. You don’t need to be a top-notch
scientist to realize that water and acid aren’t
good things to pump through the lubrication
system of the engine. If an engine is run long
enough for the engine oil to warm, the water
and acids will evaporate and not accumulate.
But, during very short trips in cold weather,
water and acids can enter the engine oil and
cause the oil to "wear out."
Second, the degradation of the oil and its
additives. We mentioned earlier that a number
of additives are put into oil to improve its
performance. If these additives are degraded
or decomposed, the oil is no longer capable
of doing all of its jobs properly. Oil with
degraded additives can become thick and
dark. Additives become degraded by exposure
to extreme heat. There are two places a
lot of heat can reach the oil. One is near the
combustion chamber. Oil at the top piston
ring is exposed to very high temperature.
And some bearing surfaces can also put a lot
of heat into the oil at high operating temperatures.
So, degradation of additives from high
temperature operation is the second factor
that can cause oil to "wear out."
How Can Operating
Conditions be Used to Predict
Oil Life?
Using carefully controlled laboratory
tests, it’s possible for lubrication engineers to
measure how long it takes to dilute engine oil
during cold operation. And it’s possible to
measure how long it takes for high temperature
to degrade the additives.
We usually think of measuring time in
hours and minutes, but for an engine, the
amount of revolutions it has run is also a
good measure. So for the purposes of oil life,
time is measured in engine revolutions.
Engineers like to talk in terms of models.
A model is a way to describe something
mathematically. It’s possible to create an oil
life model that very carefully matches the
results of analyzing the oil in a laboratory.
The oil life monitor, then, is based on a
model. A computer chip in the Powertrain
Control Module is loaded with a certain number
of engine revolution counts. The count
for each engine/vehicle combination is determined
by testing. As the engine runs, each
revolution is subtracted from the remaining
count in the oil life monitor. When the count
reaches zero, the instrument panel light
comes on. But, here’s the clever part. When
the various input sensors detect that the
engine is running under either cold or hot
conditions, it subtracts extra counts (penalties)
for each engine revolution. So, the conditions
that cause the oil to "wear out" make
the counter run down faster.
When the oil is changed, it’s necessary to
reset the oil life monitor (see the February
and March 2000 issues of TechLink) and the
countdown begins again.
NOTE: Synthetic oil resists "wearing out"
better than mineral oil, so the oil life monitor
is set to account for this, but only on vehicles
that are specified for synthetic oil from the
factory -- the Corvette, for instance. Using
synthetic oil in other vehicles is certainly not
harmful, but the oil life monitor will continue
to count down as though the engine contained
mineral oil.
- Shirley Schwartz contributed to this article

[20inchaurora]

thanks aurora40, that was very informative, now i am much less reluctant to let the oil run in the car till it tells me to change it

[Aurora40]

You're welcome. It's a pretty smart system. I usually change oil around the 15-20% mark, though, but it usually works out to about 6,500 miles or so.

I think GM must have been hesitant to use this initially. My 1990 Corvette has an oil-life monitor. The owners manual tells you how to reset it at each change. But the maintenance schedule does not tell you to use it. There are fixed intervals, and I think a note to change it before the interval if the light says to (like if you pick the light-duty interval). Maybe they wanted to put it in the field for a bit before totally trusting it to work.

[20inchaurora]

yea, mine was still at 54% when i changed it, but i suppose i will wait it out till about 20% the next time. 45 bucks an oil change really isnt that cheap, and i wouldnt mind stretching it out to half as often if it wont harm my car at all

[Aurora5000]

I change my mobil 1 around 7k which is around 10-15% left on oil monitor.

[GlennS87]

I also use Mobil 1 but I change it when the monitor says so.

[20inchaurora]

thanks for the input guys i appreciate it...seems as though the verdict is i could go at least double what im goin with the oil now

[scottydl]

And maybe even more... from what I've read, the monitor recommendations are based on the car's usage assuming you're using dino oil. It doesn't know if you're using synthetic, which is obviously much longer-lasting.

[oldsfanatic]

Mine goes to around 6,500 and the monitors ~15-20%. Seems this is fairly consistent with others. Isn't the light driving change 7,500 miles?

[20inchaurora]

guess i'm just old school....was brought up to change oil at 3k religiously. but thanks for the info guys i appreciate it greatly

[rocketman]

I'm sorry, I have to disagree. I change Mobil 1 in my car (formally cars) every 2500 miles. In my opinion it has nothing to do with breakdown of the oil. It has to do with dirt. I want all dirt out of there sooner than the recommended oil change intervals suggest.

[Aurora40]

What kind of dirt is getting into your oil?

[20inchaurora]

im assuming by dirt you mean contaminants? and if so you bring up a good point. synthetic gets contamintaed just as quickly as dino juice...just breaks down much more slowly, which is why i am weary of changing it over 3k. because 3k mile old dino juice is gonna be just as "dirty" as 3k mile old synthetic ya know?

[Aurora40]

Actually, your car has a filtration system built into the oiling system. Dirt shouldn't be a problem unless you drive in really dusty conditions. Also, there are additives in oil that handle the contaminents. This is precisely what the oil-life monitor is monitoring. Synthetics do have higher amounts of additives generally, and the oil itself breaks down less, also consuming less additives.

If you did oil analysis and said that it was too "dirty", then that would make a reasonable argument. To suggest that it didn't occur to oil and lubrication engineers that oil might get "dirty" when they came up with this scheme is a bit unlikely.

[20inchaurora]

i misspoke, when i was saying "dirty" i was referring to contaminants, IE what makes the oil appear dirty, either carbon or microscopic particles that dont get filtered out or so forth. from all the research that i have done, it seems to me that a logical conclusion to come to is that the benefit of synthetic is that it breaks down more slowly than conventional oil.

[PurpleSplat]

I don't know about the oil life monitor... maybe I'm just old fashion, but I'd rather change it myself at 5,000km than let the computer tell me when to change it. Especially when the computer can't even get my average speed or average fuel consumption correct.

It's been telling me that I'm getting 18mpg when I've calculated it to about 22mpg.

Besides, my warranty requires me to change it every 5,000km and the place that I go too gets all their used oil picked up and recycled.

[touringsedan]

I have been using Castrol Synthetic since my 89 Touringsedan (247K miles plus), and now in two Auroras a 96 and 01. I do a lot of road miles and usually go 10K before oil change. My 01 has 87K miles now ans uses about 1 quart per oil change. I am a firm beliver in Synthetic. all of the family cars get it on a regular basis.

[rocketman]

Ever quick to respond................ (sorry, don't visit the board as much as I used to), it is the contaminants I was referring to.

A $40,000 car can get a $45 oil change every 2500 miles. A $20,000 car can get a $20 oil change or longer intervals.

Besides, I have to baby the only one I have left since I still hope to steal it away from the wife. I will tell you the '01 is no where near the car the Final 500 was. Wish I knew why.

[norbi]

In my 2002 4.0 i add about a quart every 1000 miles same as my moms 2001 3.5 Aurora and my friends 2001 3.5 Aurora.

[newtonspcs]

I've used Mobil 1 Synthetic Extended since I've owned my 2001 Aurora (3.5L) in Dec 2011. After 365 days, I changed the oil (11,100 miles) and replace with Mobil 1 5-30 Synthetic Extended and Mobil 1 Oil Filter. I usually have to add 1 quart for every 5,000 miles and this is expected because my car has 262,000 miles on it and I'm sure the valve guides have given a bit. Still runs great

[Randy T.]

How does the oil look when you drain it? 1 qt every 5k is pretty decent, I have been thinking about switching to the Mobil 1 extended myself. They claim you can go up to 15,000 on an oil change, mine holds 8 qts, so it should be able to go 20k or so between oil changes, especially considering the extra fresh quart here and there.