do you remember gasoline with lead?

[angus]

Yes.  I also remember my Daddy bitching about having to pay 40 cents per gallon of fuel.  It had been about 35 cents prior to that. 

[angus]

There are up to three different gasoline-pumps here, but all three are unleaded and differ in octane rating (91, 95, 98)... I remember the 95 and 98 being called "unleaded 95/98" on very old gas stations, though

That's the way it is here now.  Three pumps, all with varying grades ("octane ratings").  Typical choices here are 87, 91, and 93, which is equivalent, roughly, to what you call 91, 95, and 98.  (US, Canada, Brazil, etc. use the [RON+MON]/2 number.  Germany, Netherlands, Austria, etc. use RON only.  Rule of thumb is add five to the US number to compare it to the German number.)

I only recall there being two pumps when I was little.  Both had lead.  Old folks called the leaded fuel "ethyl" which is short for tetraethyl lead.  It wasn't in fuel originally, but was added as an anti-knocking agent starting in the mid-20s.  Apparently a collaboration between GM, DuPont, and Standard Oil managed to suppress government reports about the dangers of tetraethyl lead, and by the mid-30s it was added to 90 percent of the automotive fuel used in the US.  Then, when I was very young (early 70s?) I started seeing three pumps:  regular, premium, and unleaded.  Eventually there was only unleaded.  For a while, where there was both, the nozzles were different sizes.  The nozzle of the unleaded fuel was smaller, maybe only 3/4 inch in diameter, but the leaded nozzle was at least an inch in diameter.  New cars in the 70s were made with a smaller hole in the filling port so that only the unleaded nozzle would fit into it.  Either would fit into the bigger leaded port for the older cars, but the unleaded was more expensive so the older cars just used the leaded fuel.  Lots of folks would take a ball-peen hammer and expand the opening of the fuel input port on their new cars so that they could accept the less-expensive leaded fuel.  I remember seeing lots of cars with the hole widened this way.  It must have been fairly common to do this in the 70s.

[angus]

Oh, there was nothing wrong with your original usage.  I just put "octane rating" in quotes to emphasize its supercilious character.  It's an extremely misleading term.  The organic compound which is actually known as octane is a terrible automotive fuel.  I suspect its "octane rating, if tested, would be far too low to use in a car.  I think that the term comes from the fact that one of the common names of 2,2,4-trimethylpentane is isooctane.  But then again 2,2,3,3-tetramethylbutane could also be called isooctane.  In fact there are about 9 compounds which could be reasonably called isooctane. 

In any case, I just wanted to point out a conversion factor for comparing US (Canadian, Brazilian, etc.) "octane ratings" to those in other countries.  Kinda like what we call "seventy-one degrees" you call "twenty degrees."  Although the "add 5" rule is still only a rough estimate. 

Note that the octane rating is not a measure of the enthalpy of combustion.  Pure ethanol, for example, has an octane rating of about 100, which is the same as the octane rating of pure 2,2,4-trimethylpentane, although they have very different thermodynamic properties, as discussed elsewhere.

memphis actually reminded me that some cars also have specific octane rating guidelines in the owner's manual.  I had a car once whose owners manual suggested 93 octane or higher.  It was a German car, however, and although all the other parameters were in English units (the fuel tank capacity was listed in units of gallons, the speedometer had units of mph, the outside temperature thermometer read in degrees Fahrenheit, etc.) At first I'd always put premium fuel into it, but I decided at some point that the engineers who wrote the manual had not converted the suggested octane rating to the US system, and that what it was calling 93 was what we would call 89 octane, which is actually the mid-grade fuel in much of Pennsylvania, and the lowest grade fuel available most gas stations in Iowa.  I even experimented with it, using all different fuel grades available, and just as with every other car I ever owned, I could detect no difference in the fuel economy within my ability to measure it.

Now, there may be some long-term advantage of using other grades.  I was looking specifically at the number of miles I could drive per gallon of fuel.  The detergents do have some beneficial effect on the moving parts of the engine, and deposition of unburned hydrocarbon soot can also have a long-term effect on the points, exhaust, plugs (if you still have those), condenser, etc.  Different brands of fuel (e.g., "Chevron with Techroline") can have an effect.  I'm a a big fan of the empirical method, to be honest.  Want to answer a question?  Just perform the experiment.  That's always the best way to get the answer.  (Well, except when, as I have often learned the hard way, the experiment offends others.)

[angus]

Ah, yes, I remember benzin (I lived in Germany for a year, and in Netherlands for a semester)  We actually use the same word for the aromatic compound, C6H6, except that we spell it benzene.

The various companies have various trade names for their different grades of fuel.  Regular, Super, and Premium are common names.

Well, for some questions such as "Is it true that if you fart loudly in a crowded elevator people will get off at the next floor?" the experiment can be tough.  (It is true for about 40% of the population, by the way, according to my tests.)  There's a television program here called Mythbusters, their deeply-held philosophy being that the empirical method is the only true way to settle arguments.  I like it.