Total Miles to Empty reading

[jamesstock]

I've been filling Premium gas from Chevron since new (except the first tank which the dealer provided and I had no idea what gas they put in). I recall first few tanks fill up, the mileage till empy will read around 430-450miles. After about 6 months or so, the reading after fillup would read 370-390miles. Then for a few more months it would continue giving me such estimate until 2 months ago when the gauge would give me back to 420. ALl these times I've been putting in premium gas from Chevron. I've always drive the same route (back and forth to work / home / malls..same routine all the time). Last 2 tanks I filled up Shell Premium gas and the read dropped to 370miles. What the heck is going on? Does the brand of gas really matters? PS. I change oil every 6k, full synthetic mobile 1 w/ K&N filter.

any reason different gas would give me almost 10% difference in mileage reading? How do I get back up to 440 area (when new)? I don't think the break-in preiod was bad since I always take it very easy on the paddle (<3k RPM), 80/20 hwy/local.

[EXceptional]

Maybe for you, one Gas Company's Fuel has different Octane levels than another one does, even though they are both dispensed as "Premium".

Or maybe "Regular" Gasoline was dumped into a "Premium" Gasoline Holding-tank?

My Dad used to work for Texaco Canada... and he said it was common for Refineries to help each other out during their time of "Shutdown" or "Plant overhaul"... so you really don't know whose Gasoline you're buying.

[Avalanche325]

I am sure you average MPG varies a bit. So if you keep your foot in it (I know nobody here would do a thing like that), or traffic is heavy, your milage will go down and of course, so will the range.