This is a strange one. I found a station that has 91 Octane pure gas, no Ethanol and filled her up. I went to below a quarter tank to keep it from being diluted by what was in the tank. 91 Octane is the highest we can get out here.

My mpg went from 31.2 to 25.6 on that tank. So, on a trip, on Saturday, I filled back up with 10% Ethanol, 91 Octane, and my mpg went up to almost 30.

I have never noticed this in the past. I have seen just the opposite, in other cars.
Does anyone have any thoughts on this. The price is the same, and I didn't notice any difference in drivability.

I would have thought the pure gas would have provided better mpg, and even increased power.

 

That is crazy. On all of my vehicles it is the opposite. My suburban drops the most.

 

Could be any of a million variables. It's very rare for someone to drive exactly the same after each tank of gas.

 

was that gas bought from a reputable place? meaning shell or esso or some other big chain gas pump?


Maybe it was advertised as you say but you weren't actually getting what was advertised.

 

I never use anything but a brand name gas. This was Mobil. I formally used only Tier One gas, but the local companies have removed those signs from their pumps.

 

Use Gas buddy or another app like it. It will tell you the tiers. My family use to be int he gas business. If you stick with the tire ones. Mobile, Sunoco, Union oil, Chevron,Texaco etc you will always be good. most manufactures use Chevron for testing well they use to.

 

weird... I guess.... you should likely just buy the good stuff from another Tier 1 brand pump and see what the outcome is.


I know I've accidentally bought 85 in the past when I've visited the US ( I forget the US sells the really cheap stuff)


and it cost me a lot less to fill up my tank, but I got A LOT less mileage as well from the 87 octane fuel I normally buy.

 

Joe, you are right, the 85 octane is crap, but here in Western South Dakota, it is higher priced then Mid-Grade. No one can figure that one out. As far as using Tier One, the local stations have removed their Tier One signs from the pumps. So, I am not sure the local distributors are actually supporting the Tier One program. And, Gas Buddy did not list Tier One stations in my area. Welcome to the Twilight Zone

I have gone back to the Mobil Premium with Ethanol, and the mpg went back to 31.2 on a recent drive, after a second fill.