Can burning some oil be a GOOD thing?

[MavRick]

Can burning oil actually be a good thing? Common sense tells me that if heavier weights don't burn and lighter weights do in a particular vehicle, then the heavier weights might not be getting into the places it needs to to do it's job. Common sense also tells me that burning oil causes deposits and emmissions that can't be good. So should our goal be NO oil consumption, or just a little?

A curious mind wants to know

 

[Ken2]

The pistons and cylinder walls need a very small amount of oil film for lubrication. This oil film will be burned off during the combustion stroke. The proper amount of oil film is so small that the consumption may be hard to see on your dipstick...and it may be replaced with contaminants added to the oil so the engine doesn't appear to burn any oil.

Ken

 

[pedaltothemetal]

Burning oil is normal if you don't see it coming out your exhaust in the form of blue smoke. Then your rings or valve guides may be worn which can be seen on high mileage cars mostly after cold starts, or when you decelerate and the vaccum draws oil past the guides and rings.

 

[Patman]

I have a similar situation where my car uses some oil however it's leaking not burning (for the most part) I haven't fixed it simply because I don't want to tear down the motor just to fix a 1qt per 6000 mile leak. I also feel that by being able to top up the oil so often (I add 100 ml every 1000km) I am safer with my extended intervals than an engine that consumes nothing.

 

[Pablo]

As the others have said, some oil will be burned "naturally" when oil is doing it's job(s) -that said:

Burning oil is not good for so many reasons that it kinda, sorta outweighs any reason for saying that the actual burning is a "good thing"....(the lubing part is good, the burning part not)

1) oil in the combustion chamber rapidly decreases the octane rating of the fuel mix - power output can be noticeably diminished - especially in forced air vehicles, such as turbos that require the ability to have higher pressures without predetonation.

2) As per #1 this predetonation can further harm the engine.

3) As per #1 - all things being equal (and I know they rarely are) cars burning high amounts of oil get worse gas mileage. Take two exact vehicles, driven exactly the same, etc - one burns say a qt in 5000 miles, the other a qt in 1000 miles - dollars to donuts the lower oil consumer gets better MPG.

4) Burning oil in a IC spark vehicle is not good for the environment...costs money too.

5) It poisons the catalytic coverter eventually and speaking of cats - for awhile they do a pretty good job of torching off oil, so the blue smoke is minimized...

I guess it depends on how much "some" is - my Volvo 245Ti with 234K miles - amazingly burns very little oil. I do 10,000 miles oil change intervals - and the make up oil is somewhat dependent on "turbo use

" but I end up typically using less than a quart.....

edit=fixed a phat finger typo

[ December 13, 2002, 07:42 AM: Message edited by: Pablo ]

 

[Patman]

I had heard in the past that Ford specifically designed the 302 engine to burn a little bit of oil in order to increase it's longevity. History suggests that might be true.

 

[Al]

quote:

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Originally posted by Patman:
I had heard in the past that Ford specifically designed the 302 engine to burn a little bit of oil in order to increase it's longevity. History suggests that might be true.

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Ford needs all the longivity it can get

Just kidding. The 302 is a great engine.

 

[Kernel Potter]

I've heard people say that Porsche 911s use quite a bit of oil and the explanation is typically that they are designed that way. Maybe under certain conditions there is something to be said for oil usage and longevity? Or maybe just a brush off to explain oil consumption problems? Does anyone else have any ideas?

 

[Patman]

Take this for what it's worth, as the info came from friend's of mine that I used to hang out with (and race with our 5.0 Mustangs) But what they said specifically was that the Ford 302 was designed to allow a little bit more oil to get past the rings than a normal engine, that way it created a bit less friction, so that the engine would last longer. Most people I knew with 5.0s would burn about a quart every 3000 miles, and in some cases as much as a quart every 1000 miles if they really drove it hard. But Ford said anything around 1qt per 1000 miles or better was normal (in other words if you burn one quart every 1.5k they do nothing about it but if you burn one quart every 800 miles they will fix it)

And I'm sure everyone on here knows about someone with a Ford 302 that has gone 200-300k or more.

 

[dickwells]

Examination of the clearances in a race engine seems to indicate that designing to burn some oil is useful in engines that will see very high RPMs and loads more than occasionally. I don't think its of any value to burn oil in a "road" engine. What part of the 302 is supposed to live longer due to oil consumption?

 

[Dr. T]

My owner's manual: "Some oil consumption will occur and is normal depending on driving style and type of oil used". Some engines are designed to use oil eg. Mazda Rotary.

But, by enlarge I don't think you can make a blanked statement like "it's a good thing". Some consumption can be deemed as normal and we need to diferentiate that about 1qt./1k mi. is acceptable, but more than this may indicate engine wear/damage or internal problems that need to be addressed. I think the ideal would be zero. I remember one person once telling me that his key to changing the oil is "when the level starts going down".

 

[carl97ss]

Some hi-perf engines are designed to burn some oil. My small block, bored and stroked 396, burns oil but it is because the small block stroked engines create quite a bit of sucking on the down stroke forcing oil up past the rings. A new ring package is needed on mine.

the Mazda rotary engines were designed to burn some oil.

 

[MavRick]

quote:

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Originally posted by Ken2:
Those might be the words that dealer's guy told your dad, but the meaning was, "Ford isn't paying to repair that engine...get used to buying oil." A quart per 1000 miles might be normal (and probably wasn't); it certainly wasn't right.

Ken

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For that engine design it might have been normal, but remember this is in the early 70's. I personally woudn't want to be adding 1 quart every 1000 miles and would consider it a big inconvenience if not a flaw for a modern vehicle.

 

[Chris A]

quote:

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Originally posted by Pablo:

1) oil in the combustion chamber rapidly decreases the octane rating of the fuel mix - power output can be noticeably diminished - especially in forced air vehicles, such as turbos that require the ability to have higher pressures without predetonation.

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I don't think that when the engine burns oil, even at the 1 qt/1k miles rage, there is a signifigant amount of oil to effect the octane rating.

If car averages 25 MPG, it is going through 40 gallons of gas over that 1000 miles which it burns 1 quart of oil. This would put your Fuel to oil ratio at 1600:1. I seriously doubt that will effect the octane rating.

 

[Chris A]

Forgot something in my previous post.

Aren't MMO, Lucas UCL, and Schaeffers Neutrea 131 mostly oil?

 

[UncleS2]

40 gal. gas to 1 qt. oil = 160:1 gasil ratio, not 1600!

 

[Chris A]

quote:

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Originally posted by Stuart Hughes:
40 gal. gas to 1 qt. oil = 160:1 gasil ratio, not 1600!

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This is correct

. I was in my 12'th hour of work when I posted that.

I may also be wrong about the UCL's being oil based, but I'm pretty sure I read something to that effect.

 

[MavRick]

quote:

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Originally posted by Chris A:

quote:

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Originally posted by Stuart Hughes:
40 gal. gas to 1 qt. oil = 160:1 gasil ratio, not 1600!

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This is correct

. I was in my 12'th hour of work when I posted that.

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Hope you aren't in charge of running something critical like a Nuclear reactor (at least not in your 12th hour of work)

[ December 13, 2002, 11:48 PM: Message edited by: rgiles ]

 

[eldawg4100]

caddy northstars really burn the oil also!

the hone pattern of the cylinder wall is very agressive...thats why it eats oil. although, it has a problem with getting carbon on the rings and consuming ever MORE oil.

 

[MavRick]

Wow this turned into a good discussion! Lots of good ideas and I've learned a bunch. I got to thinking that burning just a little bit of oil may help in the boundary lubrication areas because you are getting lubricants past the rings (hopefully a small amount). Also I've noticed some people have stated that they need to add a quart every 1000-3000 miles yet get high mileage out of the engine. My dad mentioned to me he had a new '72 Ford Pickup that would drink 1 quart every 1000 since new, and the dealer told him that was normal usage.

I usually never add oil to my cars (except a 302 engine in a 76 mustang) but that could be because I haven't been checking it often enough (until now), and if it's in the cross hatched area I leave it alone (which means I could have been using up to a quart between changes and not noticed). I'm keeping a close eye on my '02 Explorer with a 4.0 SOHC V6 engine and a Toyota with the DOHC V6 both running Mobil 1. Will be interesting to see if they use oil. Since Mobil 1 runs thin at temp, I'm assuming it will use some.

Anyway keep the ideas and knowledge flowing