Quality of Gas to MPG

Personally I have never found any real big differences in MPG when using Top Tier Gas vs. Cheap Gas, therefore I just keep using the cheapest gasoline available (ie. Costco, Arco, Pemex (Mexico), etc.) Other than that, I use a fuel system additive/cleaner every 5000 miles along with a tire rotation & balance.

But to be honest, the one thing I have noticed which makes a big difference for me was tire pressure. I generally get about 52 to 54MPG, when my tire pressure is set at 42psi (Front) and 40psi (Rear). I always check my tire pressure about every 2 to 3 weeks.

 

If your Yuba City is in California like google suggests, then you already have ethanol in your petrol.

As for efficiency vs. brands (and/or vs. octane) that is a highly charged debate.

My personal experience:

RX350, RX400h, and the non hybrid Civic EX all work best on Shell VPower (91 octane because of the altitude, the highest grade available here).Fuel economy is notably different. In the RX's slightly better but not much. Premium is required anyways, so Shell premium vs. whatever else premium is essentially the same and any extra is made up for in the minimal fuel efficiency. The civic however can be run on anything, and it likes vpower. usually 4mpg better, no idea why. Chemically, it should be worse for that engine, but it isn't. Go figure... The price delta is more than made up for with the fuel savings.

As for the Prius and the Civic Hybrid, they really don't care. I got no better or worse fuel economy with one brand over the other or grade. Since Shell is the closest, that is what I use, but both of them get 85 octane el cheapo and do just dandy.

 

Temperatures have been warming up in your area. I would assume it has to do more with that than the formula of fuel you are using. We should be moving to summer blend fuel soon if we have not already.

 

No difference. Differing blends such as gasohol will make a difference, but the OP stipulated against that.

Tom

 

You might have gotten some summer blend gas. Also, warmer temps probably help.

 

From what I understand it all comes out of the same pipe but the top tiers add more stuff.

At the current cost I use whats cheapest.