What Is Winter Grade Fuel?

Do you ever wonder why you seem to get worse gas mileage in the winter compared to the summer?

There are a few factors that contribute to this. I will focus on the biggest, which is the switch from Summer Grade fuel to Winter Grade fuel. Not all states across the country switch grades, there are a few factors that go into who does and who doesn’t, so some places get the same grade of fuel all year long. The switch usually happens in the fall and the spring, and isn’t officially announced.

So let’s ask the most obvious question first, why is there a switch to begin with? The simple answer is to promote Clean Air.

Pollution is a major concern during the summer months due to an increased level of smog and ozone. The heat actually boosts the formation of ozone, and can create an immobile layer of air called an Inversion Layer, that will trap pollutants in the lower atmosphere. Here in the Salt Lake City area where I live, this is a major concern.

Let’s talk about Reid Vapor Pressure or RVP for a moment. RVP is the measure of the gas pressure in a closed system measured at 100°F. Fuels that have a higher RVP evaporate more easily than fuels with a lower RVP. So, you can probably work out that the summer-grade and the winter-grade fuels will have different RVP numbers, winter being a higher RVP and being slightly more eco-friendly. As gasoline RVP increases, the tendency of the gasoline to evaporate or volatilize also increases. Higher evaporation rates result in an increase in emissions of volatile organic compounds, or VOC’s. During the colder months the RVP is allowed to be relatively higher. Therefore, gasoline RVP is permitted to be relatively high during colder months because colder temperatures reduce the tendency of gasoline to evaporate and reduce emissions of volatile vapors. During warmer months when ozone is of most concern, gasoline RVP must be reduced to minimize VOC emissions and, in the case of Reformulated Gasoline, to meet the VOC performance standards.

Under the Clean Air Act of 1990, Congress established amendments for a clean fuel program in 1995 to reduce harmful emissions from our nation’s vehicles. One of these amendments was the Reformulated Gasoline Program, or RGP. This program has been cost effective for the government and has provided significant reductions in air pollution across the nation. Approximately 75 million Americans can breathe cleaner air because of this program.

There is a downside however. Even though the winter-grade fuel is cheaper than summer, it doesn’t seem to be very cost effective for the consumers. From research of many vehicles, I’ve found that on average a car will lose approximately 2-3 miles per gallon of fuel mileage, which can turn into a substantial amount from your wallet.

Using my personal car for an example, this works out to be 36-54 miles less per tank. At $2.90/gallon, I’m losing over $5 per fill up, or $25 per month, just from the switch to the winter grade gas.

So, in an effort to help curb this loss of cash, I started using a product called a FuelTabs from RüK Development. You can read more about them here: http://rukse.com/chemicals-fuel-fuel-tabs.php

Since my car is a pretty new and has an efficient motor to begin with, I average about 2 miles per gallon better when using them. I don’t get all of my mileage back that I lose from the winter fuel, but I sure lose a lot less money per month. Author is Shaun and resides in Utah.