Hello -
From around the beginning of October, my fuel log tanks have been in the tank. One reason could be that I am refreshing some parts on the car in an attempt to improve my emissions (new 02 sensor, new EGR). I didn't reset the ECU/PCM to relearn because I wasn't sure if it was a good idea or a bad idea.
Now I am seeing my MPG on the decline. One reason is obviously the weather, but I wonder if the "winter gas" thing is effecting me. I was of the thought that I didn't get winter blends in Los Angeles, but now I think I do get the winter blend (probably because it's cheaper to make) :
What is summer-blend gas? - By Sam Schechner - Slate Magazine
Quote:
Summer-blend gas isn't new. It was first sold in 1995, as required by the Clean Air Act's 1990 amendments, and the current, even cleaner, concoction was phased in for the summer of 2000. Since then, there have been sharp spikes in fuel prices every spring as summer blends get rolled out. This is not so much because it's expensive to make the gas—the added cost per gallon is only 1 or 2 cents—but because refineries generally try to sell every last bit of winter fuel before mixing in the slightly more expensive summer batch. Sometimes they draw down the stock too far, creating shortages before the first deliveries of summer blend enter the supply chain. The return to normal blends in the fall causes a far less pronounced spike because the industry, free from summer standards, doesn't bother selling off the summer gas before mixing in the less pricey stuff.
So why not use the summer blend year-round? The main reason—apart from the fact that the 1990 law isn't written that way—is that summer-blend gas doesn't work as well in the winter. Summer blend's low-evaporation rate makes engines less likely to stall in hot weather but can make them difficult to start in the cold.
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Anther forum talks about same subject :
Summer Gas Blend & Better MPGs - Maxima Forums
Quote:
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- It is cheaper to make winter grade gasoline because it is possible to blend more butane into the fuel than you can in the summer, when you essentially can not use any Butane in gasoline. Butane is relatively cheap and has good octane properties. It also greatly helps an engine start when the temperature is 10 degrees below zero.
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So, I guess I do get winter gas, but I am not sure *when* I get winter gas. I did a 2008/2009 comparison, where I looked at 2 month intervals before/after October 1st :
So, from the above, in 2008 I lost 0.81 MPG after October 1st. In 2009, over roughly the same time period, I lost 2.10 MPG. That's over 1 MPG different.
Maybe I will do a weather analysis to see if there is a big difference between 2008 and 2009. Also gotta look up what mods are there/not there from last year.
CarloSW2