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By Jim Kerr

All gasoline is not created equal. This is even more apparent at this time of year, when fuel blends are changed so they will perform better as the temperature changes. If you are still using summer blended fuels, the engine will be harder to start in cold weather. This usually isn’t a problem for most drivers, as fuel tanks are refilled often. Sometimes you may get a tank or two of fuel that isn’t blended for the outside temperatures; usually, this happens because temperatures are above or below normal. The fuel suppliers try to predict weather so they can provide a proper blend, but just like weather forecasters themselves, they aren’t always right.

There is more to blending fuel than just adjusting the formula for temperature. According to Scott Rappaport, a fuel specialist from Shell’s Houston, Texas research centre, fuels also have to meet the needs of both old and new vehicles. Looking at historical data, it is predicted that by 2018 approximately 50 per cent of the vehicles on the road will be 2010 model year or older. The newest vehicles will have the newest technologies such as direct fuel injection or Homogeneous Charge Compression Ignition (basically a combination of gasoline and diesel engine ignition technology) and the fuels must be formulated to work with these technologies. At the same time, the fuels must also work in older vehicles and even antique vehicles.

I asked Rappaport if we will see a time when filling stations have pumps designated for the age of vehicle to be filled. He thinks not, but rather that future fuels can be blended so all gasoline vehicles will fill at the same pumps just as we do today.

One of the fuel changes we might see more in the future is the need for more “Top Tier” fuel. Several years ago some of the auto manufacturers recognized that emissions levels rose and fuel economy dropped if fuels didn’t meet standards for deposit control on intake valves and fuel injectors. Six manufacturers – BMW, General Motors, Honda, Toyota, Volkswagen and Audi – established minimum performance standards for deposit control that would enable modern engines to operate efficiently and invited fuel suppliers to meet these “Top Tier” standards. Currently, in Canada, Esso, Petro-Canada, Shell and Sunoco are the only major suppliers recognized as meeting the Top Tier standard.

Part of this standard is that all gasoline blends sold by the supplier must meet the standards. That means that regular gasoline is the same as premium gasoline when it comes to preventing fuel system deposits. You can select the grade of gasoline you use based on the octane requirements of your vehicle rather than detergent levels.

One of the more recent developments in fuel systems is gasoline direct injection. These systems spray fuel directly into the combustion chamber through microscopic orifices in electronically-controlled injectors. Fuel pressures are high, typically in the area of thousands of PSI, so the fuel atomizes instantly. With this high pressure pushing fuel through such small passages, you wouldn’t think deposits could build up, but they can. Tests run at the Shell laboratories on four 2008 direct-injected vehicles show that deposits can build up in the injectors in just 48 hours of operation (equivalent to 3,500 km) even with fuel that met U.S. Environmental Protection Agency minimum standards.

Using an electron microscope, significant deposits could clearly be seen in the injector nozzles of vehicles using fuel with minimum deposit control additives, while the Shell Top Tier fuel kept the nozzles clear. This was easier to identify by looking at the vehicle computer long-term fuel trim data, a number that represents the amount of fuel the computer is adding or subtracting from the base program as it adapts to variations in fuel delivery rates and combustion changes. A plus number indicates the computer is adding fuel by keeping the fuel injector open longer, while a minus number shows the computer is taking some fuel away. Injectors that have deposits in the orifices would have to stay open longer to deliver enough fuel to the cylinder. While the engine may operate adequately, the spray patterns, fuel atomization and amount of fuel injected are not correct. Performance and fuel economy suffers. The Shell scientists found that their V-Power gasoline provided an 81 per cent improvement in deposit control on these modern vehicles.

All gasoline is not equal. It may take a few tank fills, but Top Tier fuel does have benefits and with the price of gasoline, every little bit helps.

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