Fuel Additives Follow-Up

November 17, 2011

Last month, an HVA e-news article entitled A Comparative Evaluation of Prevention of Gasohol Phase Separation by Fuel Additives generated a significant number of questions from readers interested in finding out more about how they can protect their engines from ethanol fuel damage.  We put some of these questions to the author, Benjamin Kellogg, who offered his response.

Benjamin Kellogg of South Texas became interested in historic vehicles through his family’s collection of old cars, which include a 1943 WWII Jeep and 6x6, light armored 1943 M8 Greyhound.  Regular maintenance and engine repair has long been a hobby for Kellogg and his father, who last year began wondering if fuel additives might help combat the inherent problems attributed to the ethanol fuel that had arrived at local gas stations.  With an equal passion for chemistry and access to a lab at his school, Kellogg decided to find out.  With the help of a local high school chemistry teacher, Kellogg designed a simple water titration study to objectively test the effect of the additives on phase separation.

Last month, HVA e-news republished the resulting article from those tests, which originally appeared in the Fall 2011 issue of Army Motors.  If you didn’t catch the piece, A Comparative Evaluation of Prevention of Gasohol Phase Separation by Fuel Additives, click on the story link and then take a moment to see Benjamin Kellogg’s answers to some of the most frequently asked questions sent in from HVA members.

What is the baseline dehydration (life) for the gas we used five years ago?

Kellogg: How long pure gasoline can be stored varies from a few months to a few years depending on the type of gasoline—aviation gas, for instance, is supposed to last longer—and the storage conditions (cooler is better).  Predicting how long it will “last” is difficult because it is hard to know how long the gasoline has been stored at the gas station.  The biggest problems with storing pure gasoline are: evaporation of lighter hydrocarbons; hydrocarbon oxidation; and ultimately formation of “varnish-like” gum deposits.  It is difficult to tell if evaporation has happened by simple inspection of a gasoline sample, but gasoline turns progressively darker as it oxidizes.  When gum forms, small pieces can be seen in a sample.  Gasohol is less stable than pure gasoline because ethanol will absorb water from the air, thus gasohol can be contaminated much more easily than pure gasoline. It is said that gasohol can be stored for up to six months, but I have not tested this.  Water absorption by gasohol is the problem addressed by the Eastwood fuel additives that I tested.

What is the impact of other fuel stabilizers (i.e. Sea Foam, Sta-Bil, Sta-Bil Marine, etc.)?

Kellogg: While I have not tested these products, they are supposed to reduce the risk of phase separation in the same way as the Eastwood products in my study.  Sta-Bil claims to have the same effects on phase separation that the Eastwood products have but, again, I have not tested Sta-Bil.  Both Sta-Bil and Sea Foam are mixtures of different hydrocarbons than the Eastwood product I tested.  Sta-Bil contains only one active hydrocarbon agent, while Sea Foam and the Eastwood products each contain three active hydrocarbon agents (although they are completely different agents).  Since the three products are all chemically unique, knowing which is superior would require a new comparative study.

What do your results show if the amounts of fuel additive are exceeded?

Kellogg: If the recommended amounts of fuel additive are exceeded, it seems likely that the amount of water that could be retained in solution before phase separation happened would increase in direct proportion to the excess amount of fuel stabilizer used.  I suspect that the recommended amount of stabilizer is based on the amount of water that would be expected to be absorbed in six months of storage.

If the two additives [tested] are chemically identical, why didn’t you continue with your test to determine if doubling the dose of each additive on its own resulted in the same increase of water retention as the combined effect revealed?

Kellogg: Doubling the concentration of each additive would be a logical follow-up experiment, but as this was not tested, a direct conclusion cannot be reached; however, based on chemical principles, doubling the amount of fuel additive should double the amount of water that could be absorbed before phase separation happens.  But, again, the experiment has not been done so one cannot be sure.

If doubling the dose resulted in increased retention of water in E10, would increasing the dosage continue to increase the effect?

Kellogg: Based on principles of chemistry, there should be a direct relationship between the amount of additive used and the amount of water retained so that doubling, tripling, etc. the amount of additive should double, triple, etc. the amount of water retained.

At what point would increased dosage become ineffective?

Kellogg: When the concentration of the additive became so high that the combustibility of the gasohol was decreased, the additive could be considered to be ineffective at preserving the fuel. Also, if the concentration of the additive in the gasohol ever exceeded the ability of the gasoline to dissolve the additive, the additive might phase separate from the gasohol and become ineffective.  But since they are both hydrocarbons, I doubt that would happen in actual use.

Are there any other studies you are working on?

Kellogg: I started a project for the Military Vehicle Preservation Association’s Army Motors magazine to look at the effect of DOT 3 versus DOT 5 brake fluid on natural rubber and synthetic rubber that has been going on for almost a year.  I have not yet analyzed the data, but results will be coming soon.

Can you reference any studies about whether hot weather has any impact on fuel component performance?

Kellogg: I live in south Texas, so doing something with heat and gasohol stability would be useful; however, my chemistry teacher and I decided heating gasohol in the chemistry lab could have a bad outcome so we only cooled it.

Reader note: What’s your experience?  Have you tried fuel additives in the engine of your historic vehicle and, if so, did they work?  Please share your experience with other HVA members by logging a comment here or on our Facebook page.



  1. Thomas Pomeroy Buffalo TX

    While phase separation is a major concern, there are several other issues of equal or possibly greater concern other than just storage life. The fire hazard associated with fuel line and other fuel system components can should be recognized and addressed. This is apparently a very common problem in both older vehicles and small engine equipment. Octane loss after phase separation amounts to approximately 3 points and that is capable of destruction of hi performance engines in many vintage cars from the 60s or most restored racing cars.

  2. Scott Sutherland Canton, New York

    Since I had to switch to the gasoline/alcohol fuel mixture this year in my unrestored 1950 Dodge flathead "6" with 40K miles, I encountered two problems: Getting a sticky valve and/or lifter very loud noise problem that comes and goes almost every drive; had to rebuild carb this year due to parts sticking inside carb. Never had one minute of problems before change of fuels. Tried just about every additive now, including 2 cycle oil added directly to fuel. Still having problems with the valave/lifter noise, which is very loud and alarming when it happens! Thanks, Scott.

  3. Donald W. LeGoullon NW PA

    I wrote an article about preparing a vehicle for winter storage. The 'common' advise is to fill the gas tank with premium and use fuel stabilizer. I received an inquire about ethanol based fuels stating they had read that with ethanol you should leave the tank as empty as possible over the storage period. IMHO this seems wrong. Can you validate this in any manner? Thank you!

  4. Bill McKivor Seattle WA

    Am watching with interest the trial of gasahol additives. I have been using Sta-bil for some time, and not being any sort of chemist but only an observer, at least the car starts after 6 months storage. Whether the product worked as advertised is not known. However, on another matter---I have one car that has been owned for 42 years now, and in 1980 (31 years ago) changed the entire brake system out, new lines, master cylinder, wheel cylinders, etc, and thought it a good time to try dot 5. I did so. Results only from observation, but in those 31 years I have never had to add a drop of fluid, the rubber has remained supple and though I cannot see the inside of the tubes, etc, can only think the stuff works. I have other cars with dot 3, and occasionally find the wheel cylinders leaking, etc, if owned long enough. So, though certainly not scientific, my experience with Dot 5 can only be called a very good one. Will be interested to see if others have had it installed as long as I have and what their experience might be. It certainly has not rusted any connections or other parts, so it seems it does as advertised, and does not attract moisture.

  5. George Walling Merrill Oregon

    I have a 356 Porsche that when running the E10 fuel that is available at all Oregon pumps I had trouble with fuel boiling between the fuel pump and the carbs. when the out side tempature was around 85 to 90 degrees F. Here in Oregon they have in the past year allowed fuel stations to offer non-ethanol fuel it ranges around 92 octane and is unleaded fuel. It is a little more expensive than e-10 fuel by about .25 to .35 cents but since I've switched to it I have not had any problem with fuel boiling even when driving the car in 100F weather. For those who are not aware the 356 is a rear engine air cooled and the fuel pump sets low in the engine so the temperture of the engine compartment get quit warm. I have not run any tempature test on the engine compartment or any other type test other than just on my Porsche.

  6. Noel North Carolina

    Has there been any study around the relationship of blending ethanol with the different seasonal RVP base gasolines to see if there are any differences .

  7. Ken Kellow Pennsylvania

    I replaced the DOT3 brake fluid with DOT5 on my 1968 GTO in 1991. I have seen no deterioration to date (Leaking). However I have not disassembled anything to examine it.

  8. Jerry Brooks Polk County, North Carolina

    Due to the number of articles relating to possible damage in older engines from the use of water related additives in public gasoline, I checked to see if I could find a gas station which sold only "pure " gasoline. I found one about five miles away and have started using only that station for gasoline used in my two collector cars. I have found a noticible increase in engine power, and the engines run smoother.

  9. Ken Hudson North central Florida

    We and our neighbors have a number of vehicles which sometimes have the same fuel in them for months or years, in our relatively high humidity. We have never used any fuel stabilizer in any of them, and have never had a problem. Is it possible that these products are just another waste of money?

  10. Gary Decker Gaffney,SC

    I have seen a few gas stations claim they are ethonal free localally , and a few in nearby county, BUT.., i dont see how that can be true since all the gas trucks come from the same main station @ a nearby county, so i feel theres no possiable way they can offer pure gas, i have noticed poor performance in my classic 67camaro (only 91-93 octane) used from several stations, and ive been using seafoam, startron, and the new lucas addtives to help from problems related to ethnol, poor idleing, hesitaions etc, and i do keep up my vechile tune ups.....and my motors that i run on the street are 9.5 comp. ratios, and timing , mech. issues are done on reg. basis, right now i cant see where theses additives are helping me enough, and im also am using the min. dosages amounts an sometimes more, but ill continue to use em , just to be on safe side

  11. Gary Decker Gaffney,SC

    I havent seen a improvement in the fuel additives, i use seafoam alot , it does alot of things other than stabilizes fuel, i also use ethonal stabil, lucas ethonal treatment, but i cant see a differance, poor idling , hesitations, etc, we have one store , & and approx 3 more ethonal free (pure gas) stations advertise that there are " ethonal free, pure gas", but i dont see how they can say that when most of the gas trucks come from the same main station, in a nearby co. also i use only prem. gas in my 67 camaro, an my street/strip other camaro (9.5 comp motors)

  12. Ron St. paul, MN

    Etyhonal is blended when the gas is put in the tanker trucks. Tankers have serveral compartments to store fuel so they can carry different fuels and blends at the same time. I use permium BP, Mobil, Shell & Costco (which is blended with the same addative package as BP. These addative packages are added at the time when the tankers are loaded.This is only when I can not obtain non oxgenated fuel. The fuel addatives I use for storing fuel over the winter months. I dril fuel injected 280SL 71 MB