Why is oil consumption so common?

[Nick1994]

Reading through BITOG I have noticed a lot of people who are very perticular with using top of the line oil at certain intervals say their car burns a quart over 2k miles or 2 quarts in 5k miles and so on. Why is this so common, especially since it seems these cars are owned by people who take great care of them. I have a 96' Chevy C1500 with a 5.7L and 155k miles, never burned any oil, I fill it to the top line and after 4k miles or so it is still at that same line, regardless if I change with Valvoline ML or GTX HM. Any thoughts?

 

[RamFan]

Some engines are just known to burn for either known (Saturn) or unknown (Chrysler 3.5l) reasons. Doesn't mean they're going to grenade, its just a character trait.

 

[NHGUY]

Oil consumption really isnt that common.Seems some engines (Saturns) have a natural habit of it,and some that didnt break in well,or had rather in-frequent oil changes burn some too.(remember a head gasket failure can dillute the oil and add to the burning issue for the life of the engine).Many however dont burn oil.I have never had an oil burner...just a little leakers..

 

[edwardh1]

non of my hondas (3) or toyotas(3) have ever burned oil, bought new, kept til 150,000 miles

 

[123Saab]

My 2003 Ford Ranger 4.0 never burns oil. 160000+ miles.

Neither does our 08 Liberty 3.7, 69000 miles.

My Turbo Saabs always did (and do) tho.

 

[LazyPrizm]

Sometimes it's flaws in design... 98-02 Corollas and Prizms had insufficient (2) oil return holes in the pistons, which could become clogged if oil changes were improperly extended or neglected. Some folks saw better results if they ran syn from the start.

Toyota added more holes in later 1ZZ-FE engines... problem mostly solved.

 

[J. A. Rizzo]

There are so many factors that can lead to oil consumption. Some designs are more prone than others. The Cadillac Northstar 4.6 V-8 was a common oil burner, and Cadillac service at one time considered a quart every 1000 miles to be the upper limit of consumption allowed, beyond which they would perform a ring and intake cleaning procedure on the engine under warranty. Mine burned about a quart every 1500-2000 miles, and a GM powerplant engineer told me that the reason was the cylinder bore and the aggressive hash pattern that was deliberately ground into the cylinders in order to "hold" oil in the upper parts of the cylinder to keep the rings well lubricated. If the rings got sticky, they would tend to hold even more oil and it burned a lot. One of the recommendations that engineer gave me was the old "Italian Tune-up," whereby you drop the trans into 2nd or 3rd, accelerate with wide-open throttle to the top of 3rd gear (before the trans auto-shifted into 4th to prevent blowing up the engine), then coast it down with closed throttle to about 20-30 MPH. Repeat 4 or 5 times to help blow out the rings on WOT and then pull them under high vacuum as you decelerate from high RPMs. That procedure never changed my consumption, but I have definitely seen Northstars blow black smoke out the tailpipe under WOT before and heard stories about that process reducing oil consumption for others.

So cylinder bore honing patterns affect it, as do ring type, number, and positions, piston shapes, oil fill levels, driving styles, turbo/non-turbo, compression ratios, gas/diesel, oil composition, manufacturing differences... Lots of factors to consider. I don't think oil consumption is a big problem unless the PCV system is getting clogged, the intake valves or rings are getting crudded up, or the catalytic converters are getting poisoned. Northstars run for lots of miles with no problems at all from the oil consumption. Other cars might have stuck ring issues or burn through converters. I do not believe that poor maintenance is usually to blame for oil consumption. There are just too many other factors that can cause it, though lousy maintenance on a car prone to consumption might be a recipe for problems. I haven't heard many stories of Chevy 350's burning oil unless there was some other problem causing it. Your oil choice probably has little to do with it.

 

[shDK]

Taken from a danish engine tech schoolbook.

"The reason oil consumption is more and more normal. Is most off all because engine manufactores has startet to use low tension pistonrings and lower pistonskirts. The reason to do so is that the internal resistance drops in favor of lower fuelconsumption and a increase in output. As well as a longer torque curve (the torque in an engine peaks and drops again when the engine takes more power just to turn then is puts out)"

Another reason might be that when a car have a 30.000 or 40.000 km oci. It is a good thing with some fresh oil now and then.

 

[fdcg27]

The engines I've had over the years that used oil were the exception.
Most of those we've had required no adds between drains.
Now, some engines will burn off the first half quart pretty quickly while that second half between the full and add line on the dipstick will last a lot longer.
This is certainly true of our old BMW.
I think obsessively topping off a few ounces here and there will lead to the impression of an engine using oil where if the owner just left the oil level alone until it got to add on the dipstick, the engine might well reach a normal drain interval with no adds.

 

[Spazdog]

My Duratec 30 (Mazda MZI) just started to consume a little oil

About a half quart in 5000 miles. It is approaching 150,000 miles. Not worried about it. It's been run on whatever is brand name and cheap. QSGB, Mobil 5000, Trop-Arctic...etc...

There is no noticeable consumption in my wife's Turbocharged Chrysler.

My wife's old Saturn SC2 didn't have a serious consumption problem.

It consumed about the same as my 2 year older D16Z6 Civic EX did. Can't explain that one.

All of my VTEC Hondas have consumed oil depending on how much time I spent on the big cam lobes. Drive nice and stay out of VTEC? Virtually no consumption. Rev it up and let it switch over to the high lift/long duration lobes? It'll consume. Especially my GS-R.

 

[edwardh1]

moms buich leaks oil

 

[Cold_Canuk]

New Subaru FB25 engine has oil consumption issues.......sucks to own one........

 

[Hermann]

Both Ford Vulcan V-6 I have owned used a qt every 1500 miles like clockwork. The Vulcan in my mom's 2000 Taurus uses about a qt every 2K. I had a Chevy Vega that used less. Usually could get to the 3K OCI without topping off.

My 2.7L I-4 Tacoma uses none. My Honda K24 used a very small amount. The late GF's Duratech V-6 used none till 70K then used a lot all of a sudden. My Ford 250 I-6 used none. The '68 Olds 350 4-bbl used none, but loved premium leaded gas at 10-12 MPG. The Foci's 2.0L Zetec used a bit but never enough to add. I guess it just depends on the engine in question.

 

[fdcg27]

That differs from my experience with the Vulcan.
We had a Vulcan in our '97 Aerostar and it used very little oil, such that adds were never required between drains, which were always 4-5K.
OTOH, my old Vega could not possibly have gone even a 3K OCI without adds, probably not even a 1K OCI.

 

[Michael_P]

Q: Why is oil consumption so common?

A: Thin oil

Actually my 1997 F150 4.6 uses 1/2qt every 7500 miles and it has 229,000 miles on it. I use M1 0W20 from time to time.

 

[lyondell]

Aluminum pistons expand and contract with temp. changes. Piston ring gaps have to allow for this expansion or contraction.If two or more end gaps align , you will have greater oil consumption.Factory calls for end gaps to be 120 -180 degrees apart.Sometimes this isn't the case.Believe it or not hyperautectic pistons expand less than forged.

 

[demarpaint]

Originally Posted By: Michael_P
Q: Why is oil consumption so common?

A: Thin oil

In many instances thin oil is the cause, in some situations it can be a remedy.

As far as the car makers stating it is normal to consume oil, and no set amount is given it's actually pretty simple. They are just covering their arse, and all bases. The amount varies case by case, and is usually based around how much oil the individual customer says they're using. In other words a customer says: "my car is using a qt. of oil every 600 miles", the tech says, "500 is considered normal." LOL

 

[JOD]

I don't think 2 qts per 5K is common, at all. A quick look through the UOA section shows that's quite unusual. I also don't think consumption has increased. If anything I think on the whole consumption in engines has decreased. It's just more noticeable since factory OCI's are longer. With a 3K OCI, 1 quart every 10K isn't that noticeable; over 10K, it's noticeable.

All cars consume some oil, it's just more noticeable when you extend the OCI. Over the last 30 years I've been driving, it seems that on-average cars consume less oil now than in the past.

 

[Garak]

Originally Posted By: shDK
Another reason might be that when a car have a 30.000 or 40.000 km oci. It is a good thing with some fresh oil now and then.

For sure. Plus, one doesn't notice consumption if the oil change interval is way short.

 

[troyb43]

I went 22,000 miles last year on a 2009 Focus. It used no oil. Blackstone said to try 24,000 next run. My 1973 Chevelle was lucky to make it 3,000 before using a quart of oil.