Are we paying more for cheaper gas?

[SnoManX]

I've noticed this past year that my Silverado 5.3 has been getting lower gas mileage. I went from normally getting 15-16 mpg to now getting 12 - 13 mpg. I had it into the shop at 93k for it's 100k tune up thinking that would help - nothing. Brought it into another shop to get tires this fall and asked them to look over it also but they said everything was up to par.

I asked a buddy who has the same year truck and he says that he's averaging around 11-12 mpg when he was usually getting 15 mpg and my girlfriends little 4 cyl Escort is getting 100 miles less per tank. Has anyone else noticed this with their vehicles?

[bonefish]

I spent several years working for a refiner and marketed refined fuels, so I'll try to answer some of the perceptions you've got.

First, can one brand have better quality gasoline or diesel than another? In short - NO. Every gallon of product coming out of a refinery or terminal has to be within a narrow set of specifications for that product (87 octane UL, #2 Diesel, etc). It's no secret that refineries like to make money, so they are going to aim for the minimum specs and are losing money if they error on the high side. The only difference you get is in the additives a "Brand" will put in the gasoline. This has some effect in gasoline, but a larger effect on diesel engines now that we are using ultra low sulfur and have to add more additives for lubricity.

Another question was the adjustment of alcohol/ethanol in gasoline. In MN we are a 10% state. Every gallon sold (except for non-oxy off-road/outboard type use) is going to have 10% ethanol. That doesn't change throughout the year. E-85 however, is actually only 85% ethanol a few months of the year. It spends most of the year at 70-80% ethanol. These blends are adjusted on a set schedule throughout the year to meet avg engine specs (octane, vapor pressure, etc) throughout the year based on the temperature.

There was some question about refineries in MN as well. We have two refineries in MN: Koch on Hwy 52 in Rosemount, and the Marathon refinery in St Paul Park. However, we have many others that pump directly into MN terminals from Superior WI, Bismarck ND, and Billings MT. Additionally, one of the largest pipelines in the US pumps a very large volume of product on a pipeline that originates with the super refineries in the Gulf and pumps it north into MN. With only just the two refineries in the Twin cities, most of the fuel in MN comes from these pipeline terminals. Proof of this is how our gas prices jumped a few years ago as a result of all the hurricanes closing gulf refineries. We lost a bunch of our supply. So as you can imagine, with product entering a terminal from refineries in every direction, a tanker loading up with gasoline for a given gas station, really has no idea where the product originated.

I think someone asked about Winter/vs. summer gasoline. There is a difference, but again, that difference is a federal regulation, so everyone is hitting the same specs. What changes are the products, or ingredient list used to make gasoline. You may not be aware, but gasoline is actually a blend of several different products. You don't just refine a barrel of crude oil and get a barrel of gas. It's a very complex blending process of many petroleum based products and chemicals. The adjustments are necessary to control vaporizing with the different temps we have in summer vs winter. In the summer, we don't want it to vaporize too quickly and create vapor lock, or just vaporize too quickly in the tank and engine. In the winter, the regulations change to adjust for the colder temps and the increased need for gasoline to vaporize at a lower temp to enable starting in cold weather.

I'm sure I've missed something, and I hope I didn't add to the confusion but I hope this helps at least a little.

[SnoManX]

Bonefish,

Thanks for the informative reply!

(Darn it. I thought I had uncovered a gasoline conspiracy!!)

[federline]

A can of Sea foam boosts fuel mileage, too. I remember doing some math that told me that at around $3.50/gal, I would come out ahead with my 99 silverado if I bought Sea Foam by the case and put a can into every tank of gas, because the increased miles from the tank of gas more than offset the cost of the can of Sea Foam.