ross74

I keep reading posts on relatively new DFI cars consuming excessive oil, and I thought I d repeat what I ve posted previously on the subject.

All DFI engines (indepenedent of brand) are more prone to oil consumption than non-DFI engines.
This is because they run higher temperatures in the combustion chamber and higher compression leading to a need for bigger tolerances between piston rings and cylinders to compensate for the expansion/contraction of materials with (bigger) temperature variances. This, together with the recirculation of the fumes within the oil chamber leads to increased oil consumption.

However, the oil consumption in these engines decreases dramatically WHEN the engine is properly run-in. And while the way one decides to run-in his/her car doesnt influence this, running-in the engine with long trips and lots of highway miles accelarates the engine being properly run-in. Lots of short trips in traffic have the opposite effect so a car used mostly in traffic conditions might need even more than 10k miles before it is properly run-in.

Having said that, and while oil consumption is annoying, one should primarily monitor the reduction in the usage of oil after, say, 7-10k miles. If a car continues to use a lot of oil after this period maybe i would be worried.

There will still be some DFI cars with zero oil consumption, as all engines are different between them, but on average the above is a fair representation.

Dr. Z

My 09 997.2 with PDK has used appx 4 quarts in 4800 miles.....so are you saying that highway miles should reduce the consumption.....never really heard that but it does make sense.....

mdrums

I have over 11k miles on my 09 C2S...I probably have more track miles on my car than anyone on this forum. I am noticing less oil comsumption lately. I have have done around 5 oil changes in 11k miles due to track usage. My last oil change was at 10k miles and I am now around 11,300 miles and my oil is only down to the middle bar on the oil level indicator. The last 1,300 miles have been all street miles. For street use I use to use 1qt every 600-800 miles. This seems to be improving. I wil top of the oil for my next track event in 3 weeks. I will continue to monitor the oil usage on my car.

ADias

That seems to go decisively in the right direction. If the meter reads right it's about 1/2 qt in 1300 miles.

alexb76

so do u mean this is technology related and universal across direct injection engines? If so, then why this is not the case for Audi DFI (FSI) engines?

ADias

The answer is no. Haven't you read posts by several members (myself included) stating that their DFI engines use no oil?

I've stated this here several times, but clearly nobody reads. It's not the DFI engine that consumes oil - it is the boxer engine (DFI or not) that statistically may consume some oil.

Fahrer

I see that folks keep ignoring the fact that Porsche made significant change to how the inner surface of the cylinder is formed for the 997.2 engines. This is more likely to be related to the increased oil consumption. My DFI BMW uses little to no oil. It has cast iron cylinder liners but I do expect it to suffer from intake valve carbon/sludge build-up eventually.

Bijan

Many of us have had Porsches and other cars that use no oil, so technology (specially in 2009 and at Porsche) can and should produce precise parts that will be well within tolerance in nearly all their engines.
Just a thought but maybe it is the parts that cannot be precisely controlled and unique to our engines, namely imperfections in the cylinder liner coating. I am not sure if the 997 still uses Nikasil

Nissan uses a thicker process that can be machined/honed to have controll over the process:
http://jalopnik.com/5467038/the-ford...he-nissan-gt+r

Footnote added: Fahrer I had the same thought

mdrums

Oil consumption has NOTHING to do with DFI. There are other brands of DFI engines that use little to no oil.
Like Fahrer said Porsche changed the metal on the cylinder walls. I believe this has a lot to do with the oil consumtion. I also believe and I will probably get flamed for this but I think Porsche's spec tolerences are wider than most other brands. Some engines are just tigher than others.

Is there an issue with all of this? Well I certainly believe so but Porsche does not. I hope I am wrong though and we will only know what all this means many years down the road. Unless you know the engine designers closely and personally at Porsche but even if you did all you would probably get from them is, " I know nothing"!

ross74

Dr. Z: What I am saying is that highway miles (instead of start-stop miles) accelerate the run-in process. When the engine is run-in properly (as in fully) oil consumption should steeply reduce.

ADias: I disagree. I have been working in the car industry for years, and it is common knowledge amongst us that DFI engines MAY consume more oil than non DFI ones. This is true independent of brand. It does not mean that all DFI engines will consume oil (as some posts keep stating that they know of some DFI engines that don't - of course that is true). All it means that the DFI technology inherently increases (because of its combustion characteristics) the tendency/probability to consume oil. Now, as stated, the Boxer architecture, dry sump (or semi dry-sump), high rev engine, materials used ALL are elements that lead to a tendency for oil consumption (again not true of all engines - each one is different).

With DFI in particular as time goes by those of us that use that engine will notice a steep decrease in consumption as the engine is run-in, thats all I am saying.

On whether oil consumption in itself is a bad thing, the answer is, as with all things whether it is an engine design feature (as is with Porsche engines due to all the above) or an abnormality. If a Toyota consumes lots of oil it would be worrying. A Porsche, or a BMW M5 consuming oil is not.

alexb76

So, the Porsche engine design feature is to consume oil? My car hasn't consumed even a quart of oil in the last 8 months, 5K miles, and through 1 track day (albeit non-DFI).

I agree that high performance engines would consume more oil than for instance a Toyota, due to the higher RPM, heat, and typical driving style of high performance cars... but I find it hard to believe the Porsche DFI engine is designed to consume more oil. If so, that's a design flaw IMO.

V.A.G.

alexb76

Well, I was responding to ross, not yours.

I got no oil consumption at all, on my boxer engine (997.1), and know of many Audi FSI engine that consume little oil, so found it interesting that ross claims FSI/DFI consume oil by design.

ross74

Didn't say that DFI engines consume oil by design!
I said DFI engines are more prone to oil consumption by design, and this is a different statement.

It simply means an engine which would consume statistically 0 oil before would probably still consume 0 as a DFI but an engine which would consume say for example 250ml/1000 miles before might consume more as a DFI because of the different piston rings and materials. So if before the 997.2 generation came out, consumptions of more than 1qt of oil per 1000 miles were rare and potentially worrying, with DFI I would wait until the engine has been run in, piston rings and seals settled and then see what the consumption is, as simple as that.

ADias

I do not buy your argument. I would bet that the oil consumption statistics of port injection and DFI in PAG's boxer engines are probably similar.