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Save Valuable Money 

  Thanks to Sheriff Buford T. Justice:


The big oil companies have been trying to buy this column for months. Apparently, it took a check for six figures - that was a long time ago. - to get the 100-mpg carburetor. And you've heard about those gas-tank pills: just drop one in the tank with every fill and your mileage quadruples. That buyout had so many zeros it looked like a Hollywood movie deal.

The oil barons do what they have to do: over the counter, under the table, cash by the Samsoniteful, check, or money order. But I have to stay lily-white, be cause I'm neither confirming nor denying a run for the presidency in '92.

What the oil companies didn't want me to write - because it would put a heckuva dent in their profits - is the tip that could save you up to a shiny quarter cash money on every gallon of gas you buy. It's easy: no wrenches required. Just roll on by the super-premium pump and fill up with no-lead regular.

Some cars benefit from fuel higher in octane than the 87 PON (pump octane number) of regular unleaded. But not many. In fact, one of the most exotic engines on the market today runs happily on regular: the 24-valve V-6 in the Taurus SHO. Above 3600 rpm, it delivers its full output on 87 PON gasoline. Premium and super premium add nothing but gravy for the oil companies.

Ford recommends premium fuel for the SHO V-6. It's plainly a high-performance engine, and Ford decided upon premium way back in the concept stage to avoid design constraints on power out put. But when the job was finished, the resulting engine worked fine on regular fuel, primarily because modern engine technology eliminates the bungling operation that, in past engines, could only be smoothed over by high-octane fuel.

Detonation - the "ping" we've all heard - is the sound of out-of-control combustion. The spark plug's job is to start the fire. As the flame front travels across the chamber, the pressure and temperature rise in the mixture yet to be burned. The farther the flame has to travel, the higher the temperature and pressure rise. If they rise high enough, or if there is a hot spot, spontaneous ignition can occur somewhere in the remaining mixture. That's trouble.

But four-valve engines usually have the spark plug centered in the chamber, which means a short flame path to all the extremities. Therefore, the intentional fire completes its job before spontaneous combustion has a chance. Port fuel injection delivers a more uniform mixture to all cylinders, which means there isn't one somewhere that's way ahead of the others in its propensity to ping. And electronic engine-management systems are more apt to spark each cylinder at exactly the right time, which also cuts the chances of an early pinger.

David Beatty, a product-design engineer on Ford's SHO project, likens premium to a log and regular to sawdust. Both will burn, but sawdust - with any excuse - goes off in a flash. A log, like high-octane gasoline, resists immoderate combustion. A truly modern engine, however, controls combustion more by design than by fuel…

Above 3600 rpm, the SHO has no need for premium. But what about at lower engine speeds? In laboratory tests under adverse conditions, premium fuel allows a little more spark advance without ping. That advance translates into a torque increase of about three percent at lower speeds. But out of the lab and on the road, SHOs don't ping on regular. Beatty said that last summer Ford engineers drove several test cars with the knock detectors disconnected and never heard a sound. The factory-set ignition timing is right for best torque with premium fuel. If you have regular in the tank and the engine pings, the electronics will pull back the spark, thereby reducing torque. But if the engine doesn't ping, the spark stays where it was set and you get all the torque there's ever going to be. Beatty says spark pullback is a possibility - maybe if you're towing a trailer through Death Valley with a carboned up engine - but not likely

Contrary to what most motorists think, premium fuel doesn't contain more power per gallon than regular. They're the same. The power comes from having enough octane to allow optimum spark advance. If your engine doesn't ping on regular, premium will do nothing for you. Moreover, most engine engineers will tell you that a modest amount of part-throttle ping bothers you more than it hurts the engine.

Although I haven't talked to engineers from every company, I think it's likely that most modern car engines have no more need for premium fuel than the SHO's does. Turbos are a major exception. Some turbos are has-been engines being squeezed for a last bit of juice before retirement. They have outdated combustion chambers. Add to that the extreme temperatures and pressures from the turbo and you'll want all the detonation insurance you can get.

Other turbos are highly sophisticated. Saab's system, for example, listens for the onset of detonation and sets boost accordingly. Hose in a dose of Mexican regular and power will drop to the mañana level. Buy the good suff and power will climb in lock step with octane up to 92 PON. Octane ratings above that may make you feel like you're giving the engine a treat, but the engine won't notice.

So, unless you're driving a turbo, premium is largely a placebo. But, hey, people like placebos. That's why such a word had to be installed in the dictionary. And that's why extra pumps are springing up at gas stations. The oil companies have discovered, to their delight, that people will pay up to twenty cents a gallon more for a gasoline better than the premium they already don't need. Hence we now have super premium. Financial analysts say oil companies are harvesting 50 to 60 percent of their gasoline income from these placebos.

Within the trade, this deft mining of customer psychology is called "retailing." The art of retailing is why when you stop, for example, at one of Ashland's Super America stations, you have to walk through a maze of display racks thrusting at you Charms, Chuckles, Chiclets, Cheese Doodles and Chattanooga Chew before you can get to the cashier to pay for your gas.

Perhaps this is only right, because if you spend the money for a chew instead of premium, your engine will never know the difference.

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