Question - why am I having slightly increased oil consumption?

I have about 140K miles on this "new"engine (about 187K miles on my 2000S chassis) and am noticing a slight increase in oil consumption. Any ideas as to why?

- This engine used no more than 1 quart of oil between 15k oil changes over its 140K miles - usually just a half quart
- Now it just used up 1.5 quarts at about 8K miles since last oil change and I see no spotting on my floor
- I see no smoke nor experience performance changes
- Seems to use it during long higher-speed highway trips but I am not really sure of this
- I noticed that when I used 0 weight oil, I would get spotting on the floor but using heavier stuff it stops
- Mechanic put in something else other than Mobil 1 last change.... synthetic... but I can't remember the brand .... I trust him, he is a well established Porsche indy for many many years...

If I understand your post correctly, the higher consumption started after your last oil change when a different oil was used for the first time.

If that's the case, that would be my first guess, that it has something to do with the new type of oil being used. I'd get your mechanic to switch back to the oil you were using before and see what happens.

Doesn't sound like anything to worry about aside from keeping a careful eye on your oil level until the next change, unless you start seeing oil drips or notice the car smoking.

Have you checked your coolant? Does it still look clean or is it taking on a muddy look, which would mean the coolant and oil getting mixed.

I just seems like quite a coincidence that that was a sudden change after you last oil change.

it gets cleaned up by the cat once the motor is warm. When cold one can see blow-by.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

could be xw30 vs xw40; or simply a 40 (high) weight that either has a lower cSt at oeprating temp; or used more VIIs that simply break down with age.

Or simply bad luck.

Or car running hotter.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I thought as a car ages, shouldn't you use on 05 vs 00 weight oil? Maybe they used 00.

Quote
db997S
I thought as a car ages, shouldn't you use on 05 vs 00 weight oil? Maybe they used 00.

with now over 250K miles on the engine, the oil consumption is not affected if I run Mobil 1 0w-40 vs. for instance Mobil 1 5w-50.

Sincerely,

MarcW.

First, theoretically, a 0w40 and 5w40 are both 40 weight at 100 deg C, which is operating temp. In practice, the 0w40 will likely be a bit thinner, and *may* require VIIs to achieve the range, which means it will shear down over use. But its vastly more complicated than "use 5w in older cars" and according to ACEA and SAE, dead irrelevant. Their specs say anything-w40 must meet the same viscosity specs when warm.

In fact, there are often bigger differences between brands and formulations than between the same manufacturer's 5w40 and 0w40.

In my experience, as it ages, the only prominent 0w40 (Mobil1) does begin to thin and can then burn.

But that brings us to the other part of what to do with older cars. Many older cars remain tight. I had an Audi with 300k miles that used no more oil than it did new. Of course, even new it used some oil. I have trouble believing that the poster's car suddenly became loose coincident with this oil change. It had to be something related to the change, or to a change in driving conditions. Or i should say its highly likely to be so.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
grant
First, theoretically, a 0w40 and 5w40 are both 40 weight at 100 deg C, which is operating temp. In practice, the 0w40 will likely be a bit thinner, and *may* require VIIs to achieve the range, which means it will shear down over use. But its vastly more complicated than "use 5w in older cars" and according to ACEA and SAE, dead irrelevant. Their specs say anything-w40 must meet the same viscosity specs when warm.

In fact, there are often bigger differences between brands and formulations than between the same manufacturer's 5w40 and 0w40.

In my experience, as it ages, the only prominent 0w40 (Mobil1) does begin to thin and can then burn.

But that brings us to the other part of what to do with older cars. Many older cars remain tight. I had an Audi with 300k miles that used no more oil than it did new. Of course, even new it used some oil. I have trouble believing that the poster's car suddenly became loose coincident with this oil change. It had to be something related to the change, or to a change in driving conditions. Or i should say its highly likely to be so.

Grant

Porsche doesn't give blanket approval to all oils that claim to have the same ACEA and SAE classifications as oils that are on the list.

Since I (apparently the only one in the world) have some confidence in the approved oils list, what I take from this is that the ACEA and SAE classifications are getting so loose that just because an oil meets one/both of these doesn't mean, well, much.

Were my Boxster or Turbo using too much oil I'd try some other oil, maybe. Maybe not.

For one thing the choices are limited as long as one stays on the reservation regarding approved oils so my thinking is one approved oil is pretty much like any other approved oil. Thus it would probably be simply a matter of luck to find an oil, stumble upon a different yet approved oil that benefited oil consumption.

Unless a seal is leaking, or the AOS is under performing and allowing too much oil vapor to pass through into the crankcase (which I think often accounts for higher than normal oil consumption) the real problem is the engine is burning oil, the engine (or parts of it like rings/pistons/cylinders or valve stems/guides or just valve seals) are worn, have developed looser clearances and the natural result is the engine is using oil.

It is hard to imagine two approved oils having such different molecule sizes that one would not as readily flow past areas where another would.

In the case of the OP, I think he ought to return to whatever Mobil 1 oil (the 'heavier stuff') he was using before this last oil change and whatever oil was used after which he noticed the increased oil consumption.

I would suspect this oil is to blame, unless the OP's changed his driving style/habits and this accounts for the increased oil consumption.

Also, in the case of the OP, having to add 1.5 quarts in 8K miles is not bad. That is about what my cars use. The oil level starts out at the max line and then I drive the car and when the oil level drops to say mid-point between the max and min lines I add enough oil to bring the level back to near the max line. Then by the time the oil has dropped a maybe at most another couple of bars the second time the oil is due to be changed (at 5K miles). I might add long road trips can have the car covering nearly 5K miles with little oil consumption. It is those hard acceleration blasts up to near redline through the gears that really see the oil level drop over a short span of time.

To me having to add a half to nearly a quart of oil once every 5K miles between oil changes is not the end of the world oil consumption. I do not think it worth experimenting around with various oils in hopes I might stumble upon an oil that would improve upon this oil consumption, that's for sure.

Sincerely,

MarcW.

means that they want to independently validate claims, and that, like many other manufacturers, they have requirements that go beyond ACEA specs. For example, VWAG in their 505 series have tests for long change interval. What exactly they are, i have not bothered to decipher. Since i don't use long drain intervals, i don't particularly care.

I agree that testing leaves lots of wiggle room. I also agree that confirmation by porsche has some value. But i also understand that manufacturer validation and endorsement often comes via commercial agreement. let's not be naive. It sucks, but it happens all the time.

As noted (oh wait, by me!), some manufacturers have also achieved ACEA A3/B4 approval only after many many retrys. Most of us have used that oil, BTW. A quick scan of its ration of max/min multi-vis rating indicates an oil that probably cant; meet its highest number without augmentation. And like silicone, its not quite the same as the real thing.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Now that the weather's getting "better," (meaning warmer,) are you taking longer, steady highway runs more often? The different oil is a highly plausible explanation, too.

it will be replaced by water, blow-by, and other contaminents - making the sump appear full.

But When you take a long trip, the oil exceeds 212 degF ( and goes vastly above the BP for gasoline) and all those volatiles evaporate, leaving you with the residual - the oil.

However, if your driving changed that drastically, that would be the first thing to consider. Hot oil is thinner than cold oil, so this theory aside, it would be more likely to burn. The OP (Bruce in Philly) made no mention of different driving characteristics. Bruce, please confirm.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

All good feedback and questions. I also stopped into my Porsche indy, who I trust, who did a quick diagnosis. In short he didn't find anything wrong. He hooked up the computer and everything was extremely normal. He thought it may be the oil separator and he checked this by plugging his finger over the dipstick hole to feel vacuum and felt little or according to him, normal.

The only real variable is that he used Valvoline 5W-something synthetic on the last oil change, an oil he never used on my car before. As I noted in my first post, I do notice that my car will drip 0W Mobil 1 but not a higher number. Other than suspecting Valvoline, we have no clue as to what is wrong, if anything.

The consumption appears to be on long, fast highway driving, something that I never really saw as an issue before (except maybe some spotting with Mobil 0W the next morning). There has been no real changes to my driving habits. I noticed the consumption very shortly after the last oil service. Now to be fair, the oil consumption is definitely more than normal but even then it is not by much given that this accelerated consumption can be considered normal for some cars. As I understand it.

So.... I will keep monitoring and will top off with something heavier.

On another note, we were talking about the IMS replacement from LN and he said he has done many of these and it is a very easy procedure. He said all the bearings he pulled out of the cars looked completely normal except the last one he did and said that actually had some shavings on it and was clearly failing ('99 Boxster with 90K miles). He couldn't find it in his shop to show me as the other mechanic who used it for show and tell had left for the day. So when I then asked him what he thought of doing the procedure, he kind of shrugged and was non-committal except that he did save one engine from imminent failure. I kind of laughed and said that I thought I may actually would prefer a failure as we could put a bigger engine in my car.... it is still cheaper than buying a new one and my chassis, paint and interior are in awesome condition.

I may be mistaken, but I'd always understood that oils of different weights (viscosity?) should not be mixed.

unless there's an emergency, then any oil (almost) is preferred to running the engine with a too low of oil leve.

If one wants to switch to another brand of oil, at an oil change interval, there is no need to 'flush' the engine.

Of course the above applies to oils on the Porsche approved oils list. All oils on this list are miscible.

Sincerely,

MarcW.

I have been topping it up now with a heavier Mobil 1 instead of the already present Valvoline. I really can't see how this will hurt the car... if I did, I wouldn't do it. If anyone knows differently, let me know please. But I really can't think of why there would be a problem. I asked my mechanic about this and he said there is no issue.

So why does Porsche have this recommendation?

Quote
Bruce In Philly (175K+)
I have been topping it up now with a heavier Mobil 1 instead of the already present Valvoline. I really can't see how this will hurt the car... if I did, I wouldn't do it. If anyone knows differently, let me know please. But I really can't think of why there would be a problem. I asked my mechanic about this and he said there is no issue.

So why does Porsche have this recommendation?

It's not just Porsche that has this recommendation. I've also seen this recommendation (of not mixing different oils) in my VW and Audi owners manuals. It did state that if you absolutely need to add oil, it's better to add a different oil, rather than running it too low.

I'm not an expert on the matter, but other manufacturers seem to have the same recommendation for some reason.

Different oils do have different formulations. I'm just not sure how they interact when mixed.

Again, it's a CYA thing.
They state that because the unlikely chance that the particular oil you're topping off with may an additive that may not readily mix well with whatever oil is in the vehicle.
But all of the major brands of synthetic motor oils on the (US) market are compatible.
Just as they say that you cannot top off with any other brand than Porsche coolant.
The original coolants were developed for iron-block engines where silicate and phosphate additives were good.
When aluminum-block engines were introduced (Porsche was one of the first) phosphate and silicate additives were a non-no, so a new formula was developed.
But today with aluminum-block engines being so prevalent, all of the major brands of coolant today have a ,safe for all cars - phosphate and silicate free formula which is compatible coolant with Porsche's.
You cannot mix the old style coolant with silicate and phosphate with the silicate free & phosphate free coolants.
Happy Porscheing,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Miscibility: The engine oils approved by Porsche can be mixed with each other. This means that it is not necessary to flush the engine when the oil is changed if another type of oil is used. However, since every brand of oil has a specially adapted unique composition, the same oil should be used for topping up between change intervals, if possible.

Now thankfully many of us do not have to add oil every 700 miles, but I point out that nearly 1l per 1000km is still in the acceptable range of oil consumption.

With the above in mind, consider this: One owner might not never need add oil between change intervals, some owners (and I think this includes the vast majority of us) might have to top up maybe a quart or two between oil changes (both of my cars usually require a quart between their 5K mile oil changes) while another owner might have to add a quart (worst case) nearly every 700 miles.

If this last owner is one adheres to the recommended oil change interval, in the case of say my Boxster which is 15K miles, by the time 15K miles rolls around the owner has 'topped' up the engine with 21 quarts of oil. After a point the oil has become what it was being topped up with. But in the meantime, as soon as the oil is topped up one time, the oil becomes a hybrid. It is not what it was nor has it become what it will eventually if the topping up continues.

I do not see it a hardship at all to keep an unopened quart of oil handy in the car somewhere. And when I buy oil for an oil change I make sure I have an extra bottle or two extra for topping up. I know my cars' oil consumption and budget for this.

Now if one of my car's suddenly developed a thirst for oil and I was caught unawares (hard to imagine since I keep a pretty close eye on the oil consumption) I'd top up with some oil off the approved list, if possible -- it depends upon how low the oil level had gotten to -- but something unless I was prepared to have the car flat bedded to a dealer to have the oil topped up with something approved and therefore deemed suitably miscible.

Sincerely,

MarcW.

that advice is the simplest, least error-prone, way to dumb it down and avoid errors.

there is no technical reason not to mix any API rated oils, at least from the same Sx series. Ditto ACEA.

What can change is the effective viscosity. If you understand how it works, you can make that judgement yourself.

The additive mix could also change, which might make it slightly less suitable in meeting specific needs that Porsche wants.

e.g.: they used to want to support 24 month, 20,000 mile drain intervals. That would take some robust additive packages to fight corrosion, acid, etc for such a long time. Wisely, Porsche acknowledged (implicitly) their error and went back to something that oils can reliably meet.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

And its really simple - its an arithmetic mean. So 30 weight and 40 weight mixed 50/50 yields 35 weight.

So if you have 0W40 and the track season arrives and you want, say 10w45 -- add 50% 20w50.

I mix weights, brands etc all the time.

And my friend who formulat(ed - he changed jobs) on of the biggies does the same.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Did you remember to put the crush ring on the drain plug? I forgot to do this on my last oil change and now I have a slow leak around the plug, I'm guessing about 1/2 quart every 1,000 miles.