What octane to use?

[C J Murray]

The gas in a 356's carbs is exposed to the atmosphere through the air filter.

All carburetors are vented to atmosphere however some vent better than others, some float bowls hold more than others, and therefore the ratio of contaminating air to float bowl contents is different. This is why some engines experience problems more often than others. My mechanics often note that certain model bikes are more prone to needing a carb clean than others.

Some problems with 356s are the slow leaks from the jet holders, sometimes casting flaws, and the boiling off of gas when the car is parked. Maybe we are better off with these problems?

[David Jones]

Just to add a little more possibly worthwhile information on the E10 problem.
As has been stated now we all know the E10 blend is hygroscopic. CJ touched on the jet fouling problem. This is mostly caused by "phase separation" which occurs once the ethanol reaches it's saturation level of water. This is probably in the region of 2 to 4 tablespoonfuls per gallon. Do the math if you like, I believe the ethanol portion of E10 will hold up to 10% of water before phase separation occurs, so the amount of water held will depend on the amount of ethanol in your gas. As ethanol is not mandated on a gallon by gallon basis but by a percentage amount (must be 8% of the gasoline market in 2011) this means that not all gasoline will have 10% ethanol in it. The math then suggests that at the maximum figure of 10% the if ethanol holds 10% of 10 % of a gallon then the amount of water is going to be 37.83 cc's which is about 1.5 ounces of water per gallon or about 1.2 pints in a full tank in a 356. Double that number to add the ethanol in to the equation and you have 2 + pints of worthless liquid in your tank at worst case. I have now said as much as I want to on the problem so do as you wish with it and correct me please if I am in error on anything I have said but if you do please back up you critique with facts not conjecture or rehetoric from a website selling a fuel stabilizer.

[Michael Eker]

Average annual rainfall over 30 years.
West of Scotland 118 inches
California 17.28 inches

US lowest: New Mexico 8.91 inches
US highest: Louisiana 59.74 inches

I win that argument hands down.

The biggest problem with ethanol is with “phase separation.” That’s what happens when the fuel is saturated beyond it’s capacity to hold water in solution. Water/ethanol and gas actually separate, and the gasoline floats on top of the water/ethanol. With E10, ethanol blends more easily with any water. When phase separation occurs in E10, the ethanol is pulled out of the gas and absorbed by water. This results in two solutions, neither of which is good for the engine or fuel system…not to mention the environment. The gasoline left behind is absent of oxygenate. The water left behind now contains a high concentration of ethanol; this solution is highly corrosive and damages any material it may come in contact with in the fuel system. The only solution for phase-separated fuel is to dispose of the entire fuel load, clean the tank, and start over with a fresh tank of E10.

In just 100 days at 70% humidity, E10 can absorb enough water to phase-separate. The shelf life of E10 is only 60-90 days if left without treatment.

Of course this is only half the issue. The other problem is evaporation, ALL the ethanol can evaporate given the right circumstances.
As the manufacturers lowered the petroleum base stock octane of E10 to take advantage of the 129 (RON) 116 (MON) 122 (AKI) rating of neat ethanol, you don't need a PHD in fuel technology to see that due to phase separation, and evaporation, the octane rating of the fuel left in the tank will drop towards that of the base stock. One source puts this at 88 (AKI) against the normal 92-93 (AKI).

88 (AKI) is significantly easier for refineries to make.

They also get a tax credit for adding ethanol. This further reduces their costs.

Although, with E15 just round the corner maybe E10 wasnt so bad after all.

M.

[Chuck Wilson]

Michael
My understanding of the octanes is the ability of the fuel to burn. Low Octane burns easier than high octane. if we run high temps or high compresion engines we would go to a higher octane fuel so the fuel doen not ignite as easy.. It has nothing to do with power. As for Ethanol, whew, opening a can of worms. IT does eat up paint, so wipe after every fill up.

[Brian R Adams]

I have not experienced any problems with "E10" here, and several have so stated in this thread. However, I don't think E10 really has 10% ethanol, it can be "up to" 10%, but I have been told that what we get here in Reno is only 3-5%.

I'm sure that will be going up as the astoundingly idiotic corn ethanol subsidies get extended with $billions as part of the tax and budget compromises, and as long as EPA wields its power of proclamation ("rule making") in order to save the planet.

My point is that we may have a false sense of security about E10. If it ever does really become 10% ethanol, or even 8%, we may get a wakeup call from our engines.

Another gripe I have is that there seems to be no way to find out just what ethanol content is in the gas I am pumping. All I can be sure of is that is <= 10% according to the sticker on the pump. But if I want to know the actual formulation at a particular vendor, there seems to be no way to know. Anyone have a tip?

Brian

[Barry Brisco]

Brian, recently and in the past, David Jones, our resident oil refinery process expert on 356Talk, has posted that there is no way to know and that ethanol content varies depending on a variety of factors that the average motorist is not privy to.

Best regards,

[C J Murray]

There is enough ethanol in our gas to melt the fiberglass gas tank of my '68 Norton Fastback.

[Vic Skirmants]

Bummer. Maybe you could patch it with corn husks.

[Michael Eker]

http://www.fuel-testers.com/order_ethan ... t_kit.html

If you have E10 in your 356 that is over 90 days old it has passed its official shelf life

a test will not tell you very much as the fuel will have started to separate.

From Washington Post yesterday:

http://www.washingtonpost.com/wp-dyn/co ... 03838.html

M.

[C J Murray]

Read this link and click on "blend wall" to learn more...

http://www.thetruthaboutcars.com/2010/1 ... ol-blends/

[David Jones]

This is about the latest news there is on E15. You may notice that the EPA did a really in depth analysis of the effects of E15 on a huge number of cars (19). Unbelievable bullshit in my opinion.
http://detnews.com/article/20101220/AUT ... l-approval.
Consider this one fact and then wonder why we do not call our local politicians in every state of the union and tell them to call for an inquiry.
If you buy 11 gallons of fuel with 10% ethanol for use in a 356 (and millions of other cars)which ware never intended to use it then you will go as far as you would on 10 gallons of normal fuel. Therefore you just bought an extra gallon of fuel just to subsidize someone's brilliant idea of energy conservation and cleaning the air. Somehow does not make sense.
Hopefully the automakers will win this one but remember that the Iowa corn lobby hosts the first priamry and politicians think their primary responsibility is to get re-elected not worrying about sensible government.
Sorry Barry that is a little political but I did mention the 356.

[Ken King]

Regarding David Jones' comment, "If you buy 11 gallons of fuel with 10% ethanol for use in a 356 (and millions of other cars) which were never intended to use it then you will go as far as you would on 10 gallons of normal fuel. "

I can confirm that there is a difference in mileage from E10. Driving my BMW 530i cross country, my analog fuel mileage indicator (as well as the digital one) show hiway mileage of around 30 to 32 mpg, depending on speed when filling up in rural areas not using E 10. In Minnesota, where we vacationed last fall, they even have Shell stations that sell premium gas without alcohol (for antique cars!) and I see the same thing on my mileage. (They had no objection to selling it to me for my '07 BMW).

But as soon as I put in E10, my mileage drops to about 28. Nearly 10% poorer mileage with up to 10% alcohol, which is about what David was saying. I don't know if that is due to a computer generated change in ignition advance or what, but we are burning fuel to grow crops and produce alcohol, which seems to burn up as much gas one would use without it. What a waste of fuel, money and farm land, with an obvious negative impact also on the environment. G-r-r-r-r, thanks, farm lobby!

Let's lobby our congressmen to emulate Minnesota and allow premium gas to be produced without alcohol for use "in antique cars."

[Guest]

Well Gang,
Were now adnauseam on this topic Time to move on!! We understand we need to put some kind of gas in our 356's to make it move forward
But then again what do I know

Back under my rock I go
Cheers,
Bob Lee
356 Registry member 16135
Porsche 356 Club member
912 Registry member
Royal Dutch Shell Stock Holder

[C J Murray]

Well Gang,
Were now adnauseam on this topic Time to move on!! We understand we need to put some kind of gas in our 356's to make it move forward
But then again what do I know

Back under my rock I go
Cheers,
Bob Lee
356 Registry member 16135
Porsche 356 Club member
912 Registry member
Royal Dutch Shell Stock Holder

Bob- There is some truth to what you say but don't you think that most Registry members are smart enough to not click on a subject that makes them nauseous? This subject has popped up many times since Talk has converted to web based. There must be a little interest in it?

[Ron LaDow]

But then again what do I know

Since the subjects are clearly marked, I would suggest those wish to comment on a subject, do so.
And those who don't, don't.