Apparently, the "recipe" for Top Tier gas requires ethanol.

1.3.1.2 Base Fuel. The base fuel shall conform to ASTM D 4814 and shall contain commercial fuel grade ethanol conforming to ASTM D 4806. All gasoline blend stocks used to formulate the base fuel shall be representative of normal U.S. refinery operations and shall be derived from conversion units downstream of distillation. Butanes and pentanes are allowed for vapor pressure adjustment. The use of chemical streams is prohibited. The base fuel shall have the following specific properties after the addition of ethanol:

1. Contain enough denatured ethanol such that the actual ethanol content is no less than 8.0 and no more than 10.0 volume percent.

 

Not all gasoline that enters the combustion chamber burns. We know this cause the engine oil will accumulate gas over time.

The additive has two phases of operation: a liquid phase; a vapor phase.

A portion of the additive is intended to resist turning into a vapor as long as possible to "wash" away the deposists as the air/fuel "cloud" swirls around in the combustion chamber. Even if it does vaporize, eventually, it will resume liquid form when it comes in contact with a cooler surface.

And as with gasoline which is blended with proper vaporization one of the primary goals, upon cold start even a portion of the additive that is intended to vaporize will not completely vaporize for the same reason gasoline will not fully vaporize. Engine cold and some areas will remove heat. In fact the DFI engine's claim to fame, one of them, is by directly injecting fuel into the combustion chamber the evaporation of this fuel lowers the temperature of the air inside the combustion chamber and thus the engine can operate at a higher static compression ratio IIRC 12.5:1 vs. the older design engine's 11.5:1 compression ratio.

By being more efficient at cooling the combustion chamber DFI engines almost assure us a portion of fuel will condense out of the vapor cloud and along with the fuel any additives. This is good, at least if the additive is detergent intended to remove combustion chamber/valve deposits. Not so good cause some of this fluid will add to the fuel/water contamination of the oil this contamination occuring constantly as the engine runs though in varying amounts.

Sincerely,

Macster.

 

We in CA have no choice when it comes to gasoline with ethanol. Some areas of the country have a choice but everywhere will not as mandates to use more ethanol gasoline come down.

I will point out that I've probably driven my 02 Boxster -- with currently just over 228K miles -- more miles on gas with ethanol than many have driven their Boxsters and other Porsches on any gasoline and so far ethanol has not caused my car's fuel system any problems. I've never changed the fuel filter -- it is not a servicable item -- and have only changed the plugs at the scheduled intervals (well, intended to change them, but sometimes have run over by some thousands of miles...). Not only is the engine original so are the injectors.

Let me point out the car gets used regularly though and I have heard/read that ethanol can cause problems if a car allowed to sit long periods of time between uses, and fill ups. Gasoline and ethanol don't like to mix on a good day and given eough time for the additives intended to help keep gas and ethanol mixed to lose their potency and allow the gas and ethanol to separate and stratify into layers of each then problems in the car's fuel delivery/metering system can arise.

Sincerely,

Macster.

 

My rudimentary understanding of DFI is that the fuel burn in more efficient and less is wasted. Therefore can i infer that the fuel seepage into the oil is much less than a non DFI. tks

 

You could but you might be wrong. I too thought DFI would result in less fuel in oil but some who have more close interaction with these engines report fuel contamination still a problem.

Fuel injected at real high pressure. Compression ratio 12.something:1 high compared to older engine's 11.3:1 (IIRC). Then there are other factors that contribute to propensity of raw fuel to remain in combustion chamber long enough to make its way into the oil.

When (if) I ever get a Porsche with a DFI engine I'll probably do at least one oil analysis maybe 2K to 3K miles after an oil/filter service -- to see what kind of water/fuel build up there is just for my own knowledge. However, I'll probably stay with 5K mile oil/filter services unless the oil analysis indicates the water/unburned fuel build up so bad as to require an even shorter oil/filter service interval, which I don't expect I might add.

Sincerely,

Macster.

 

https://rennlist.com/forums/997-foru...-additive.html
Originally Posted by GSIRM3
Apparently, the "recipe" for Top Tier gas requires ethanol
Each state's Pollution Control Agency determines the amount of ethanol, if any, is in the fuel they sell.
Here in Minnesota we have three grades of fuel at most stations, 87,89,and 92. all contain 10% ethanol as stated on a sticker at the pump. However, some stations also sell 91 octane non-oxy fuel. The sticker on that pump says, "Non-oxygenated fuel, for use in outboard motors, lawnmowers, collector vehicles only". The good news is we do not employ fuel police here. Also, the Minnesota Street Rod Association publishs a list on stations that sell the fuel in the state. The state has a very strong street/hot rod community and they lobbied for the fuel. Each summer, the state has the Minnesota Street Rod Association which attracts over 10,000 vehicles over one week. see link here.
The good news about the non-oxy fuel is the better power/economy, tank life, and fewer effects on engine parts.

 

Sorry for the jump.
I did not find what the bottom line is.
Is it recommended to use fuel additives in our 997.2?
(BTW, in the user manual it is specifically written not to use fuel and oil additives...).
If the answer is positive. Should you use additives on a full tank of fuel? How to apply?
Is it recommended to put a fuel additive before changing the oil or does it not matter? (I'm curious because I don't have an oil change soon).
Thanks

 

i can’t give a definitive answer , but I have used Techron for 38 years since I purchased my 1985 911 new, and I have noticed a few things.

At about the time of my purchase, the carbon build up issue was showing up, and the fix then was to blast the valves with crushed walnut shells. Porsche also recommended “spirited driving”, which I interpret to be an “Italian tune up”. About that time, Porsche expressly recommended Techron. This was before the Top Tier rating for gasoline came about, I think. However, there were warnings about the need to change the oil if more than one bottle of Techron was used; these warnings may even have been on the Techron bottle. And , of course, this was before the use of synthetic oil, which may be relevant.

so my practice was , and is , to use a bottle of Techron in my 1985 911 about two tanks prior to my annual oil change, which was about 3000 miles, and with 125,000 miles on the odometer, my 911 runs beautifully.

as I accumulated DFI vehicles, I initially continued the Techron supplement, but the oil change interval was about 5000 miles. but most of what I read indicated that the use of Top Tier gasoline would be sufficient. I also noticed that the label on the Techron bottle stopped mentioning carbon build up, but focused on cleaning the fuel injectors. And , of course, I became await that Porsche no longer advised using additives, but did urge the use of Top Tier gasoline.

i concluded that Porsche was ok with additives in the gasoline as long as the amount was controlled, that is, the concentration included in the Top Teir gasoline, but my belief was that Porsche was concerned that it’s customers couldn’t be trusted to use an additive in moderation, and thus contaminate the oil, thereby causing real damage.

this is just my opinion. Mike

 

2009 C2S 185K miles

I put in Techron every once in a while, usually the last tank before an oil change and many times on a long trip... just running the engine tank after tank on the interstate with Techron.

What did it do? What didn't it do? Performance change? I dunno. So why do I still do it? I dunno.

Peace
Bruce in Philly (now Atlanta)

 

The decision on whether or not to use a fuel additive may depend on how your car is driven. If it's a very low mileage car and spends some extended time at rest in the garage, having an additive would make sense I think.

I use Sta-Bil 360 in my current air-cooled 911, and also used it in my 997.2. It protects the fuel from prematurely going bad. (Stale fuel produces varnish that ends up in the tank and is distributed throughout the fuel system.) Sta-Bil 360 also helps negate the affects of Ethanol in fuel.


I also use Techron Concentrate Plus Complete Fuel System Cleaner (20 oz bottle) once annually. I put one bottle in the tank when it's 1/2 full - and run the heck out of the car, letting the engine get up to full temperature. Then I let the car sit in the garage for a couple of days. The thought is that the concentrated Techron mix will help dissolve / eat away any deposits in the fuel tank / system. After that I fill the tank, run the car on that, and then refill again when that tankful is used up. Then change the oil.


To Bruce's point - does it work? To the extent that I can tell by driving the car and the difference I can feel - before / after the treatment, I think yes, it does help.

 

I've started looking into fuel additives more and more recently, especially those that include higher levels of PEA, a component known for its strong carbon cleaning properties. Whether these additives work or not may depend on the shape your engine is in and what you're trying to accomplish with the use. I have a very specific use case, which is oil consumption due to carbon build up around the oil control rings. This is most likely a result of long oil drain intervals by some of the previous owners earlier in the car's life. Car has new UAOS and bore scoring has been eliminated. I've noticed the following changes after using some fuel additives. Initially, car would consume around 1qt of oil per ~600 miles or 1000km. This is within Porsche spec but seems excessive. By running products such as BG 44k and RedLine SI-1 (both contain highest levels of PEA I was able to find), I saw an improvement of 1qt per 950 miles. My theory is that the rings did not get clogged up in hard carbon over 1 or 2 long drain intervals so it will also take time to fix this chemically, without opening up the motor. So do fuel additives work? I think they do - it just depends what your expectations are and in what shape your car is. Hope people find this data point useful.

 

Thanks friends!

It was very interesting to read everything.

It's hard to sum it up. I think I'll wait it out and consider adding a fuel additive before the next oil change.

The reason I considered putting a fuel additive is because I have an unstable idle (like many 997.2) I replaced all the vacuum tubes, TB and still, no change. By the way, the MAF is original, and there is no fault code, happily.
But the idle is unstable (jumps between ~640-672-704~ RPM). I would also be happy to know how to read the misfire data.

In addition, There are many values ​​that I do not understand the difference between them:
misfire counter = All values ​​are 0
misfire counter 10 trips = All values ​​are 0
misfire control operate counter =
Cylinder 1 - 3
Cylinder 2 - 2
Cylinder 3 - 9
Cylinder 4 - 4
Cylinder 5 - 0
Cylinder 6 - 3
and misfire counter for every ignition = value is 54339

I'm interested if this live data of misfires can shed light on the unstable idle.
I am considering opening a new thread in this regard.