JBD

About a month ago, I asked for your help finding our why there are three grades of gasoline. Now, thanks to the crack JBD investigative team, I can reveal that there are actually only TWO grades of gas produced by refiners.

Thanks to a wayward driver, one of the pumps at my local Mobil station (the one where White Lightning used to melt wrenches with car batteries to amuse local hoodlums) was damaged to the point where they couldn't get the cover panels back on. So they just wrapped it in clear plastic, awaiting repair.

Today I go to fill up (at $1.99 per gallon, fer chrissakes!) and being the Nosy Nate I am, I took the opportunity to check out the guts of the pump.

The pump has three grades available - 87, 89, 91. There is only one pump nozzle, and you press a button to select your grade. Lo and behold, my inspection of the pump guts reveals that there are only two input pipes coming up from the underground tanks, both feeding into individual filtered pumping meters, one marked LOW OCTANE, the other HIGH OCTANE. Their outputs then feed into a manifold (a mixing chamber), with a single pipe feeding from the manifold up to the nozzle. 

So my guess is that if you select 87 or 91, the appropriate pump works at full speed to feed the nozzle. If you select 89, both pumps run at half speed, mixing the fuel in the manifold, delivering a mix that averages 89 octane.

This means that if you follow a driver who bought 91, and you pick 87, you get a little higher octane until the hose and manifold are flushed out. The same goes for buying 91, following someone who bought 87, but you get a small amount of low octane first.

I wonder if this system works the same for pumps that have individual nozzles for each grade. My guess is that most stations have moved to the one nozzle system, saving money by eliminating two nozzles. I'll have to start noticing this as I drive around. Inquiring minds want to know!

This makes a lot more sense to me. There are really just two grades available to serve both the low end and high end of the market. And for just a little more hardware cost up front, the oil companies earn an extra 10 cents a gallon from people who think slightly higher octane gives them value. My idea of injecting octane boost on the fly would be just as expensive as the current two-tank system.

While this also kills my idea of simply converting one nozzle to a flex-fuel ethanol/methanol feed, they could still easily convert one feed to pure ethanol/methanol, leaving the other at high octane gas. Ideally, this would be even better than just one or the other. You could then dial in the mix you wanted based on your vehicle, the comparative costs of the fuels, the kind of driving you're doing (local stop-go or long distance), vehicle load, etc.

A simple calculator (which many cars already have) would allow you to feed in these factors and give you the best mix to use for lowest cost per mile (MP$ vs. MPG). The pump system would then adjust the two pump speeds to feed the right ratio into the manifold, delivering to your tank the custom blend you want.

There! With the stroke of a key I've reduced our energy crisis by one-third. So now I can move on to perfecting the flyin' car.

Posted by: JBD at 12:15 PM | Comments (1) | Add Comment
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