There is a thread on this topic and I think it was around 2007 Feb,. A study was done on this site By Wilson I believe and Shell indeed came out ahead.It was a interesting thread! Hal

 

I use Shell gasoline probably 80%+ of the time. I started using Shell because Honda recommends using "Top Tier" gasoline of which Shell was the only brand I could find either in town or along my commute. I've never tracked my mileage by type of gasoline, but given the Honda recommendation, it would seem that it is possible, especially as you rack up the miles.

As I understand it, "Top Tier" gas was an effort by several auto manufacturers, of which Honda was one, to recommend gasoline with certain detergent qualities to prevent build up on the valves, etc. I tried going to toptiergas.com (where I first looked into what gasolines where so designated) but the site seems to be gone/down. Shell is now marketing their gasoline as having a nitrogen additive. Not sure if, or how, that relates to the future of the Top Tier designation.

Here is a link to a "Car Talk" column on TTG from the Washington Post in September 2007.

 

Maybe it's a bit of a gamble, with any station, due to the various factors already mentioned. Every once in a while we seem to be getting better mileage than usual, other times worse than usual. I can't see one brand consistantly delivering 10% better mileage. We're partial to Chevron, but I don't think there's a lot of difference between any of them.

 

Agreed that there are many factors that impact mileage on individual tanks/trips. Interestingly, however, Chevron is listed as one of the brands of Top Tier gasoline.

 

Shell and Sams Club gas come from the same refineries. Shell trucks leave with their marked tanker trucks, and Sams club leaves the same refineries with white unmarked trucks.

In Texas, the blend of gasoline changes with the seasons ( ethanol content percentages). this has much more impact on mileage than the brand.

 

What’s more, your local Chevron station may sell gas refined by Shell or Exxon Mobil. Suppliers share pipelines, so they all use the same fuel. And the difference between the most expensive brand-name gas and the lowliest gallon of no-brand fuel? Often just a quart of detergent added to an 8,000-gallon tanker truck.

http://finance.yahoo.com/family-home...d=family-autos