What would you think of a gasoline additive that increases your mileage by 20%, horsepower by 10% and decreases emissions by a whopping 70%? All for only 10 cents a gallon. Not only that, but the fuel burns at lower temperatures, so there’s less wear and tear on the engine.
Sounds like something advertised on late night TV, right? Or perhaps rumored to have been suppressed by the oil industry.
Well, according to Science News, just such a additive has been discovered and it’s not even some esoteric mixture. It’s polyisobutylene (PIB), the main component of synthetic rubber.
Has anyone ever heard of using this as an additive? I’m wondering if it was discovered years ago but rejected (or suppressed) for some reason.
If not, any idea when/if it will be added to the gasoline you buy at the pump? Would something like this have to be tested (again) by a government agency (EPA, maybe)? Better, might the EPA require it to be added to gas?
[I searched the web for news on it, but the only thing I could find was that someone adds PIB to oil for 2 stroke engines, getting much of the benefits I described above.]
My Aldrich catalogue shows polyisobutylene being sold as a chunk for $66.30 for 250 grams. Granted the scientific grades are more expensive than the industrial grades but I don’t think the difference would be that great. Note also polyisobutylene sold through Aldrich is a solid.
Well, good person, being a naturally skeptical person I would think is akin to the “Platinum Gas Saver”, magnets on the fuel line, the “Evap0-Carburettor”, et al. I apologize, but being an ME I hear an awful lot of ads for “miracle additives” or “dongles” to increase mileage, lower emissions, and so forth, and they almost all turn out either to be frauds, or impractical, or both. It would be interesting to see if someone else here can provide additional info to justify or shoot down my assumption.
The EPA and others are mandated to test anything that gets added to gas by a wholesaler, for such things as it’s effect on various types of emissions, toxicity, safety of use, storage requirements, etc.
I’d like to. This was from a report submitted by Paul F Waters of American University at the 220th national meeting of the ACS. But I can’t seem to find the abstract on the net. Maybe you have a better idea of how to find it.
As far as the MTBE fiasco, yes that will probably make the EPA more cautious. For those unfamiliar with the MTBE case here’s a summary of it.
After doing some more research, I find that PIB compounded with amine and/or other chemical groups is already used as a fuel additive to clean fuel injectors. But I’m guessing in smaller amounts than was used in the tests reported at the ACS meeting. Perhaps this means that the EPA doesn’t have to approve it. Then again, the compounding probably makes a difference.
dtilque, the dose is what makes the poison. The EPA may have limits on how much of this stuff can be added.
I wonder if this will affect air/fuel ratios. Carbureted cars may not run well with it, and modern injected cars may interpret it as a problem with the engine.
It’s been decades since I took physics, but I seem to remember that the efficiency of an engine was computed by comparing the internal temp with the exhaust temp. The greater the difference, the more efficient. (This leads to the idea that if you use some of the energy produced by the engine to cool the exhaust, you can raise the efficiency of the engine. I never understood this concept.)
According to the article, PIB works this way:
Gasoline is composed of a variety of hydrocarbons. The shorter ones are more volatile and burn first. The longer ones are less volatile and burn a bit later. The later burning hydrocarbons are what produce incompletely burnt hydrocarbons and also raise the exhaust temperatures since some unburnt hydrocarbons oxidize in the exhaust. The quicker burning ones produce engine knock and also the most heat.
Polyisobutylene delays the burning of the short hydrocarbons so that all the gasoline vaporizes and burns at more or less the same time and thus more completely. They didn’t really explain why this reduces engine temperature although my guess would be that the excess heat from the short hydrocarbons goes into completely oxidizing the long ones rather than heating the engine.
At any rate, the more complete burning reduces the incompletely burnt hydrcarbon emissions and the lower engine temp reduces nitrous oxide pollution. Since there are fewer unburnt hydrocarbons in the exhaust, its temp is also reduced.
As to how PIB works, Waters suspects that it changes the surface tension of fuel droplets which keeps short hydrocarbons from immediately vaporizing.
They claim to have tested this on a dozen different cars, both in the US and other countries. The article didn’t say what adjustments, if any, they had to make to the cars.
It turns out that the article in question has been posted to the web (Science News doesn’t do that for many articles). Here’s a link:
Not quite. What you are thinking of is the sensible heat loss of the engine, which is a function of how much higher the exhaust outlet temperature is from the reference temperature (measured at the air inlet to the engine). As the temperature of the exhaust approaches the temperature of the reference air, the efficiency increases.
Well, sort of. IMO this is an oversimplification that does not explain what could yield such a reported increase in engine efficiency.
My guess is it would be an evening out of the heat flux, so there is not so much of a temperature spike when the volatiles combust.
I agree with lower temperature = lower NOx, as this is well proven just by looking at Gibbs Free Energy measurement, and the equilibrium constant of the NOx formation process. But I question again just how much unburned or unoxidized hydrocarbons are in a modern FI engine. My understanding is on a heat-input measurement basis, unburned combustibles contribute less than 0.3% to the overall efficiency losses. And again, I question the effect of reducing these unburned combustibles on engine temperature. In fact, if one reduces unburned combustibles to 0, if all other things are equal, wouldn’t the temperature increase overall, since more energy is released?