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March | April 2007
Volume 81 Issue 2

Auto Talk

Gasoline octane levels in Colorado

The most noticed number at the gas pump is usually the price you pay. However, in Colorado you should also be paying attention to another number — the octane level of the gasoline you're pumping into your car. Colorado is among a group of states where regular unleaded gasoline has a lower octane level (85) than is normal elsewhere in the country (87).

During the past few years, AAA Colorado has received numerous letters from members regarding the octane levels of gasoline in Colorado . What do octane levels really represent? Why is it different here? What's the best octane for each car?

To begin with, octane rating of gasoline is a measurement of the fuel's ability to resist knocking or uncontrolled burn. Many years ago, research by the American Petroleum Institute showed that the lower air pressure at high altitudes allows vehicles to perform as well on 85 octane as they would on 87 at a lower altitude. The Colorado Legislative Council contradicted that research in a 2001 study, which showed that the altitude difference might apply only to older cars (pre-1984). Despite this new information, there has never been any change to Colorado 's 85 octane standard, which was set decades ago.

Many consumers and gas producers save money as a result of Colorado 's lower-than-average octane requirement. Because it costs more to produce 87 octane than 85, oil refineries save money by providing 85 octane as regular unleaded in Colorado. As a result, Colorado residents often pay less at the pump for gasoline compared to many states.

As long as the regular unleaded gasoline octane level in Colorado remains at 85, the best advice is to check your owner's manual, consult a qualified mechanic or check with your vehicle's manufacturer for the best octane to use in your vehicle.

If you use 85 octane regular unleaded and hear your engine making a pinging sound, it could be a sign that your engine is not running efficiently on this gas blend and you should try 87 instead.

As manufacturers continue to develop improved engines that automatically adjust for the altitude at which they operate, there might come a day when Colorado makes the switch to 87 octane regular unleaded. Until that day, the best advice is to pay attention to how your car operates.

For current gas prices visit www.aaa.com/gasprices.


Is your car overweight?

The car is fully loaded with passengers and luggage, ready for your weekend trip. There are five seat belts, five passengers and at least five pieces of luggage. So you're good to go, right? Not necessarily—if your vehicle is overweight it could be potentially hazardous.

Every vehicle has a manufacturer's recommended payload capacity that is the maximum combined weight of

all cargo and passengers that can be safely carried, not including towing. Exceeding this payload capacity stresses the tires, shocks and springs—three parts of a vehicle that keep it under control and on the road.

Drivers can find out how much total weight their vehicle can safely carry by looking at the sticker on the driver-side door panel. For example, a 2005 Nissan Quest minivan can hold seven passengers and has a payload capacity of 1,200 lbs. If each of the passengers weighed 200 pounds, the vehicle would be considered overloaded even without luggage.

An overloaded car is a safety hazard even if it is well-maintained. When a properly inflated tire is carrying too much weight, it bulges at the bottom and the sidewalls can contact the pavement. As the tire rolls, the sidewalls flex up and down, heating the tire and increasing the chance of sidewall or tread failure, and a potentially dangerous blowout.

AAA offers the following advice:

    • Consider renting a car for your vacation if more payload is needed.

    • Be prepared for the vehicle to take longer to speed up, brake and steer when fully loaded.

    • Limit the number of passengers to the number of seat belts.

    • Limit any load on top of your vehicle to 18” high and no more than 100 pounds.

    • Ship your luggage separately to the destination.

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