ilovemaui

I’ve noticed that my mileage fluctuates by about 4 mpg depending on the source. This weekend I made a 300 mile plus drive to Oregon and back. My highway mileage on the way to Oregon was 26 mpg averaging about 75 mph. I filled up in Oregon with Costco fuel and my mpg dropped to 22 mpg on the trip back averaging similar speeds. I was running QFC gas on the trip down and Costco gas on the way back. Washington premium is 92 octane while Oregon is 91 octane. Curious to hear others experiences and which vendor’s gas provides the best mileage.

voiceprint1

I really try to only use Chevron 91 RON, I get around 18-20 in the city, I found the car runs through the cheap gas much faster than the top tier brands.

BucketList

Shell 91 is my preference. Chevron if I cannot find Shell. I use Shell because I heard from a local Porsche specialist that a local Dyno shop uses Shell because they get better power numbers than other fuels.

ManoTexas

Basic physics, it’s downhill from Washington to Oregon and uphill back. Uses less gas to go downhill.

street rod

You also have to factor in wind direction.

ilovemaui

Actually both Cities are about the same elevation and most of the route is very close to sea level. I have noticed this same gas mileage issue in my wife’s Toyota only in reverse, it got better milage coming home. I think it’s definitely the fuel. For some reason the Costco fuel gets lower mpg.

997ajk

with 91 octane from Costco and mostly under 30mile drives (mixed) I average 21mpg on my C4

Kineticdg

It looks downhill from Washington to Oregon, because maps are flat and Washington is higher than Oregon. However, if you put a globe on your lap with America facing up, and put a marble on Oregon, it will fall towards Washington. That is, if you believe the world is round...

BucketList

My sister in law thought Alaska was an island with a flat side for the longest time because of the way its shown on maps....

groovzilla

Recent drive from SF to Seattle I averaged 26MPG on highway at about 75-80MPH
Around town about 22.

ManoTexas

So if you use both a map and a globe the pull on the marble will offset and it won’t move.

workhurts

Wut? Did one contain ethanol and the other didn’t?

You aren’t getting a 15-20% mpg difference because of gas.

ADias

A real possibility.

David Berry

Just completed drive from Houston to San Antonio and back. Averaged 23.5 . I use Shell 93 octane

Fahrer

I have used only Shell and Costco gas in my car since new. I very often drive on twisty backroads in 4th gear and average about 21-22 mpg. On the highway I get about 27 mpg at moderate speeds.

I do not see any difference between Costco gas and Shell gas when it comes to mpg, acceleration, drivability. The only difference I see is the price per gallon.

By the way, Costco gas is Top Tier.

The amount of alcohol in gasoline varies and as indicated on may pumps an be up to 10%. This can have a slight impact on mpg. Ethanol has higher octane rating but has less energy per gallon.

My guess is that driving environment ( traffic, wind, temperature) differences were affecting your mpg. The average speed may have been the same or similar but what makes up the average speed can make a significant difference in fuel consumption.