"New" Gasoline and vapor lock

["Cadillac Kid" Greg Surfas 15364]

Prompted by the topic about a hard starting car previously posted on this forum I began to think, for the first time that perhaps another "Urban Myth" about gasoline was being established.  There is no doubt that many of our older cars DO vapor lock when hot, or even warm, but what is the true cause?
I did some research into both the history and the compositional make-up of (what we call) Gasoline, and the characteristics of additives such as Ethanol.  The simple version is that Ethanol, the accused culprit for many problems, actually has a lower vapor pressure (and thus less prone to evaporating at any given temperature) than "Gasoline" itself.
"Gasoline" is seasonally and regionally blended and the "vapor pressure" (ease of vaporization) is tightly controlled by EPA regulations.  What that means is that gasoline blended for Summer time use has a lower vapor pressure than "winter" gasoline.  Gasoline for high altitude usage is blended for a lower vapor pressure (than sea level locations) all year long.
There is nothing in any of my research that indicates the "gasoline" of today has a greater potential for vapor locking ( the boiling of liquid fuel at high temperatures and low pressure) than anything used in the past.
There is no question that the fuel value of a Gasoline/Ethanol blend is lower per gallon than straight gasoline, and that if our older cars are to operate with as much power and performance as they did on straight gasoline, the carburetors need to be re jetted and recalibrated for the EXACT fuel being used, as they were when they were designed.
The older (pre mid 60's) cars DID vapor lock when hot and that was a fact of life people lived with.  We now can readily solve the problem by installation of an electric booster pump in the fuel lines to keep the pressure in the fuel lines "up", and keep the fuel in a liquid form.
I have no personal knowledge, but one of the additional culprits, I believe" is That possibility that "Winter" gasoline, (filling the tank full prior to winter "shut-down"), having a higher vapor pressure, is still in the tank during Summer time operation.
I know this is a bit long winded, and I am sure there is quite a bit of discussion that it will generate. 
Respectfully
Greg Surfas

[R Sotardi #11719]

Pretty close to right on, Greg. We complain about ethanol in fuel and with much justification due to "rubber" being attacted etc., but a big culprit causing vapor lock is the winter gas still in the tank when air temps rise to the 90s. That's a problem here in Arizona. Around March 15 the refiners start delivering summer formulated fuels to the stations. Flash point of summer is @ 145f but winter is @ 105f. Any fuel still in your tank, or in the retailers, will raise the volitility and look out if the weather temps fly up to above 90f. Tip: keep summer fuel in the  older vehicles tank as much as possible, and anticipate your consumption.

[The Tassie Devil(le)]

Thanks for the explanation Greg,

I don't have a problem down here with winter and summer fuel as it is heavenly all year round.

Bruce.

["Cadillac Kid" Greg Surfas 15364]

Just like it is here in Southern Texas, except when it is too hot or too cold .
Greg

[TJ Hopland]

Any research into what differences there are between the various grades?    I suspect the lower grades may have more 'filler' material than the premium ones. 

["Cadillac Kid" Greg Surfas 15364]

TJ,
What we call "gasoline" is actually a blend of up to over one hundred chemicals.  They are blended to achieve the desired octane, as well as fuel value (in accordance with regulations).  Chemicals are varied to control the vapor pressure for seasonal operations (thus greater or lessor vapor pressure at a given temperature).
"Filler materials" are what "gasoline" is made up of. 
There could be all kinds of reasons for "cheaper" "lower grades", and by that I assume you mean "off-brands" rather than National distributors.
Greg Surfas

[TJ Hopland]

Im more curious about the octane.   I have noticed with older engines they seem to run better on the higher octanes.  None of them should require higher octane fuels and I am not talking about detonation or vapor lock issues.    I just wonder if the higher octanes have better quality 'filler' stuff in them or maybe they are a little more careful on the blends so you tend to get what you are supposed to get more than you do with the regular grade.

Any idea what percentage of the fuel is up to the 'brand' vs what is theoretically mandated / controlled by the government?   In our area about 90% of the gas comes from the same place but one local brand who I know is one of the 90% causes huge problems for my old stuff and lower mpg with my new stuff.  Its got to be something in their additive package.  I only have the problem with their 87.  Their 89 and 91 seem better but I still think I get lower mpg with them.   

["Cadillac Kid" Greg Surfas 15364]

TJ,
What do you mean by "older"?
What is mandated is that there be 5.9% Ethanol, verifiable octane ratings (achieved however the blender wants to do it), a specific "Reid Vapor Pressure" (RVP) in accordance with the (seasonaly and regionally adjusted) RVP/Temperature curves, as well as a fuel value that falls within the acceptable range.
You say "causes hugh problems for my old stuff". What kind of problems?
Greg Surfas

[Brad Ipsen CLC #737]

Greg, thanks for getting some science into this subject finally.  I just know enough to know that it is very complicated and beyond any simple explanations such as ethanol is causing all the problems.  In checking my 60's vintage engine text book the vapor pressures quoted are almost exactly the same as mandated now by the EPA.  I think we can actually thank the EPA for keeping the vapor pressure down.  Another case of once there is a government regulation it is almost impossible to change it.  Other than to take care of old cars, old industrial equipment, and lawn mowers there is really no reason to have these low vapor pressures for modern storage and modern cars.  They all have vapor recovery on pressure sealed systems.

[David Greenburg]

I think part of the problem with ethanol is that while it may not vapor lock more easily than "real" gas, the damage that it causes to rubber parts can cause similar symptoms.  My '59 started "vapor locking" at lower and lower temperatures.  The problem turned out to be premature fuel pump failure. The diaphragm looked pretty bad, and I think I can blame ethanol for that.

["Cadillac Kid" Greg Surfas 15364]

Since the advent of "emissions" controls we as the motoring public have been "blessed" with fuel containing a witches brew of ingredients designed to meet specific tailpipe emissions and coincidentally power our vehicles.
The results have plaid havoc with both our vehicles fuel systems and even the groundwater (remember MBTE "leaking" through the storage tanks themselves into the groundwater?).
The intent of my original post was to help stifle the urban legend about Ethanol (added) fuels being more prone to vapor locking than straight gasoline.  With the myth set aside, we can , as indicated above, get to the true source of vapor locking as it occurs.
Greg Surfas

[Caddy Wizard]

Greg,


I don't know the chemistry behind the current gasoline composition.  All I know is that the old cars with carburetors seem much more prone to vapor lock today than they did when I was young.  I grew up in the 60s and 70s in South Florida, where the temps were very high, and I don't remember vapor lock as being very common.  Just the opposite -- fuel-related problems seemed rare.  I started working as a mechanic in 1973 and I don't recall vapor lock being an issue at all.


To me, vapor lock has become a big issue for old carbureted cars.  Modern cars are impervious to the problem, since they have closed, pressurized fuel systems (i.e., fuel injection).  The carbs haven't changed, so I have to believe the fuel has changed and is the source of the problem.


The bottom line to me is that regardless of the exact chemistry behind the fuel problem, today's fuels (which are designed to be compatible with today's fuel injected engines) are not that suitable for antique cars with carbs.  Especially on cars that tend to run warm.  Frankly, I don't see any end in sight to this problem.  For me, I will keep the 2-bbl Carter WCD 742S carb on my 50 Cad, since it doesn't run particularly warm and is not terribly prone to vapor lock.  But for my 56 Cad, with air conditioning and a 4-bbl carb, I will probably switch to electronic fuel injection this winter and be done with it.  It will cost me about $1200 to do the conversion, but I won't have any more thoughts or worries about vapor lock leaving me on the side of the road (besides the other advantages of EFI, like better starting, zero percolation, better mileage, etc).  Since I drive my two Cadillacs as daily transportation in my profession (patent lawyer), I am particularly keen to ensure that the cars work absolutely reliably.  I can't afford to be broken down on the side of the road on the way to a client's office.  No, for me my old Cadillacs have to work every time or I need to get something else to drive.  On the 56, I think that means switching to fuel injection in the near future.  I have done this sort of conversion to an old Cadillac and it works great.


Art Gardner

["Cadillac Kid" Greg Surfas 15364]

Art,
A lot has changed besides gasoline since the '60s.  In 1958 I could drive from one side of Los Angeles (Santa Monica) to Disneyland at any hour in about 40 minutes.  At most hours today it would take at least 2 hours.  Traffic has slowed driving speeds down and added additional heat to the roadways.  Our cars, once new and pristine had everything working as it was designed.  Radiators were clean, water jackets were "crud" free, fuel pumps were putting out their designed pressures, and fuel systems were clean and free of debris and deposits.
Over the years much of that has changed.  I mentioned earlier that when these engines were designed, they were designwed around the specific fuels that were then available, and the carburetors were jetted and designed and tested by trial and redesign until they worked well across the range of driving conditions.
If the truth be known, Air Conditioning was originally intended to be used on the Highway where they would be constant air flow across the condenser, radiator and engine compartment.  One of the first modifications they made to Air Conditioned cars was the addition of a vapor return line to help eliminate the vapor lock.
I will repeat what I said earlier regarding Seasonally blended gasoline being stored in our tanks for extended periods (I know you daily drivers don't apply here).  Besides being blended for a season that has passed, the "open" fuel systems of our older cars allow the partial evaporation of some of the components  in the fuel, leaving a "residue" that might not be ideal.
There is no question that in our "rear view mirror" memory, there were never any problems, but the mechanical (say nothing of electronic) improvements of the last 40 years have been extensive.
Our older cars do not and can not operate and perform like the new ones if they are intended to be kept 100% original.
I have been driving my '66 for over 17 years as my daily driver here in Southern Texas.  I too have made a few concessions to modernity to keep it dependable.
Good discussion . 
Greg Surfas

[The Tassie Devil(le)]

G'day Greg,

I have to agree with you on one of the reasons for Vapour-lock, in that travelling slower over a heated roadway will cause it, as the only time it has happened to me in my '60 CDV was in slow-moving traffic, and slowly climbing a hill in 100F temperatures.

Once I could gain speed, it ceased to be a problem.

Bruce.

[Wayne Womble 12210]

Any research into what differences there are between the various grades?    I suspect the lower grades may have more 'filler' material than the premium ones.

This is from Sheets explaining how they blend. 




As you likely know, due to the EPA’s Renewable Fuels program and related subsidies; for better or worse, ethanol is now a part of America’s fuel mix.

We would love to be able to offer you pure conventional gasoline; however, there are a number of factors preventing us from doing so:

The majority of gasoline now entering the state is an 83 octane blendstock that requires ethanol to be added to make a saleable 87 octane product
Brining in segregated batches or importing pure conventional gasoline would raise the cost of the finished product; as would not receiving the 4.5 cent per gallon ethanol subsidy. This would result in a product that is significantly more expensive than the 10% blend we are currently offering. While some customers like yourself may be willing to pay extra to get pure gasoline, most would not.
Since we do not have the tankage to offer both products in many locations, we would have to choose one or the other."

I then asked how the 89 and 92 octane gases were made:

"Finished premium is created using a variety of blend ratios, depending on the area.

In PA, we use a 91 octane product, mixed with 10% ethanol (which increases octane above 92) as well as the 83 octane product (to bring the octane back down to 92 or 93)


Pure 93 octane premium is still being shipped on some southern pipelines (NC, VA, MD), but due to the second two bullet points below, ethanol is still added (taking the octane way up), then even more of the 83 octane product is mixed in to bring it back down to 92 or 93 octane."