I have been using strictly Chevron/Texaco gas in my 4Runner. With the regular grade, I was getting on the average of 20mpg.

I, then, got new tires, which were a size bigger (from 265/65/17's to 265/70/17's) and my MPG went down 1mpg (19mpg). This is, of course, the corrected figure taking into account the bigger tires. I expected this to happen.

About two weeks ago, I switched to Costco gas, since I have a membership there and their prices are usually 10 cents cheaper. After two fill-ups, I noticed that I was getting 17-18mpg. This was with the same style of driving. Nothing changed. Since I commute about 90 miles a day, take the same route and set the cruise at 70mph, there aren't too many variables that come into play when figuring out the MPG.

So, earlier this week, I switched back to Chevron and I'm back up to 19mpg again.

Has this been discussed before? I find it strange. I have not experimented with other gas stations extensively--just Costco and Chevron. Anyone else notice this?

 

I've never tried costco gas, but it seems for some reason that the gas would be worse quality, "kirkland" type stuff if you know what i mean

 

kirkland gas ?? haha

 

When I was filling out my gas sheet, I tried a few different gas stations. One perticular gas station (shell, I think) brought me down to 15 MPG!!

 

it probably contains more ethanol to get the price down. a higher ethanol content will also lower your MPG's.

 

Hmmm I have consistantly gone to shell. I will try BP for the next few tanks and see if I can get up from my miserable 15 mpg . . .

 

My truck has always ran like crap with costco gas. There are a couple of threads around here about unhappy costco gas users. I stick with Chevron. I get a consistent 17-18 mpg around town.

 

Hmm, here's my issue though: Shell carries 91 octane, Chevron only carries 90 (I would prefer Chevron over Shell if it weren't for this). I might try a few tanks of Conoco to see if there's a difference, I'm pretty sure they have 91.

 

The one trip I did to BC this summer I filled up at cheveron. (there are no cheverons in saskatchewan) I loved the gas, the 4runner ran great with great gas milage. I always run the regular gas. If your picky about octane, I don't know about down south, but the cheverons up here sell a 104 octane. That is what I ran in my motorcycles.

 

i use shell, as its the cheepest in town
might try chevron i remember my honda ran better on it.

worth a try.

 

Chevron/Texaco uses additives in thier gas AFAIK, as does shell and mobile.

The cheaper no name stations generally buy who ever offers the cheapest gas-this means it could come from any of the big companies at anytime. But I have found consistently I get exactly what yota says I am to get using any station. I got 18mpg city with my old 3.slow camry and get 16.5-17mpg out of my t100 with the 3.4L.

Also winter grade gas burns less efficent that summer grade. I dont know why really but my old camry got 19-20mpg int he summer and only 17-18mpg in winter. I think its the additives for cold weather.

It helps to keep your vehicle tuned up, I always follow the severe condtions in the manual to play it safe and have always had success. Before I had the camry tuned I got 16mpg, tuned it got 18.

 

Both Chevron and Shell are Tier 1 formulations and should perform similarly.

A guess would be the Costco is located in an area requiring more oxygenates per EPA regs that can vary by town and county, or for the reason bamachem mentioned.

Bama, does ethanol = more oxy, besides being cheaper?

 

Spot on bro.

Almost all gasoline is identical. The gas stations buy their gasoline from the same suppliers the only difference is octane. The difference is in the additives, which is why Shell and Chevron can claim a Tier 1 rating on their gasoline.

Those additives are what keeps your intake valves clean and stabilize the fuels burn rate. Cheap gas contains minimal amounts of these important additives leading to crapped-up injectors and valves. This is not snake oil, there are plenty of tests which show definitively that these additives work, unlike the cans of miracle-˟˟˟˟t gas treatment on sale at WalMart.

I use only tier 1 fuels in my cars.

As for ethanol laced gasoline; these gasolines WILL decrease your mileage because ethanol contain less energy (BTU's) than gasoline. Less energy = poorer mileage.

 

ive been using 'kirkland' gas for the last 20k miles (w/ the ocaasional whatever i can find for cheap) and have avg 20mpg the whole time.

 

Well, I'm glad I'm not the only one that's noticed this. I'll be sticking to Chevron/Texaco.

During the winter, they up the ethanol content in the gas to lessen the pollution. I haven't really paid attention lately, but there used to be stickers at the gas stations that said "10% ethanol" during the winter months. That would burn cleaner, but MPG would be affected by it, as well.

 

I do the same in my bike. Chevron is the only refinery left in BC (well Husky might still have a little teapot in Prince George) and the only gas that could be different from the rest. My bike specs 92 octane - seems you can't get that anywhere except Chevron.

All the rest come from Strathcona in Edmonton via pipeline. I know that all the various companies add their own special herbs and spices, but I've watched them do that and they add a liter to a tanker truck. I'm not convinced it makes much of a difference. You'll see more of a difference when you get winter gas vs. summer gas - the formulas change throughout the seasons.

 

Modern marvels did a show on gasoline. It showed that all gas is piped in through the same pipes. Each company leases space in the tubes. It seems to me that it kind of gets mixed together at some points. The main difference between fuels is the additives which are added as the tankers are being filled. I use Cheveron and generally seem to get better mileage than when I fill up at Circle K. I don't know what this all means, just my .02.

 

When I had my sport bike I could prove beyond a doubt that shell 93 burns cleaner than any other gas I can buy in my area. One you could smell the difference when burning, and two you could look down and see there was no carbon on the end of my pipe. If I ran any other brand, you could see the carbon within an hour or so of riding. The wife and I had been using citgo gas, untill I had to replace the catylitic converters in both our vehicles. We only run shell gas now.

 

Here's a list of the "Top Tier" fuels. Not sure how often the site is updated.
http://www.toptiergas.com