Hi all

Just came back from a 2 week many mile trip. On my last leg home I filled up my van with 91 Octane gas at Costco. I burned just over 3/4 tank getting home which is strange cause I usually have to make a gas stop just before getting home. I have done this 400 mile trip a few times.

I got an extra 40 miles out of the higher Octane gas, did the better gas make a difference or did I have a tail wind making the difference.

Just curious.

 

the quality of gas does make a big difference, but most of it notice a greater difference between bad gas stations (arco, 7-11, etc) vs good stations (chevron, shell, etc).
for that kind of mileage difference, i would test it for about 5 tanks and see if it consistently makes that much difference

 

Innumerable sources claim vehicles designed to run on 87 octane do not benefit from 91 octane & it's a waste of money. Others say if there's a small MPG increase it isn't cost effective.

Costco does not produce gasoline, they buy it on the market, making quality control an iffy business.

Claiming "an extra 40 miles" out of 400 b/c of 91 octane is probably no more likely than having "a tail wind making the difference".

 

A lot of times the higher octane gas will not have any Ethanol in it. I noticed this when buying 89 for my mowers and the 87 had Ethanol in when I filled up my P/U moments before.

 

The gas station down the street from my house sells ethanol free 93 for 30 cents/gallon more. My SRT8 loves it, and has measurably more power on the dyno.

 

Also, some places still have the 91 octane gas with NO E10 in it, witch will make a nice difference in mileage.

 

Also, some places still have the 91 octane gas with NO E10 in it, witch will make a nice difference in mileage.

 

This thread seems to have taken an odd turn? Have always read that ethanol has considerably higher octane than regular gas & that adding ethanol to regular gas raises its octane. Quick look at Wikipedia shows:

Regular gas octane 91-92 RON, 82-83 MON & 87 AKI
Ethanol octane 108.6 RON, 89.7 MON & 99.15 AKI

 

Every fuel has different energy levels and that is why I started this thread.

In the old carb days we had to manually make changes to for a different tune. Today Mustang can tell the difference between 87 and 91 gas and change the tune to maximize the power out-put.

We have O2 feedback that tunes the engine for the most efficient emissions, so but using better gas I am assuming we are getting better mileage/power.

 

Ethanol has a higher octane, but it has a LOWER energy rating. One gallon of ethanol has less energy than one gallon of gasoline.

 

Hence my comment "thread seems to have taken an odd turn". Higher octane gasolines are more likely to contain higher proportion of ethanol. Especially Brand-X from Costco.

There are several websites that help locate gas stations that sell ethanol free gasoline & explain simple test to determine if ethanol is present.

 

You'd certainly think that based on the high octane rating of ethanol, but that's certainly not the case around here. The vast majority of stations advertise their premium fuel to be ethanol free. Perhaps this is how they justify the ridiculous upcharge.

The is one station around here that does sell pure 87 octane gasoline, and their prices are typically about the cheapest around. I've noticed a slightly higher fuel efficiency in my Fusion with this stuff, but all things being equal it should only be around 3% increase in efficiency. Which at $3.00/gallon is worth $0.09/gallon.

Lots of modern engines can, but most of them aren't advertised with higher power ratings with premium fuel. The Mustang is an exception to that. These engines use adaptive spark timing that's based on the knock sensor. The engines ride the hairy edge of ignition timing, and with higher octane the PCM can advance timing further without detonation which yields more power. My '08 Dakota that I drive for work does the same thing; it specifically states in the owner's manual that maximum power can only be had with 91 or greater octane fuel. There is a noticable power increase when running E85(100+ octane) instead of 87 octane gasoline.

Now I have tracked fuel economy in my Mustang, which was tuned to take advantage of premium fuel, and noticed absolutely no increase in fuel economy with premium fuel. So I rarely bought it. If anyone cares to see my data here's my FUELLY PAGE; look at the notes for each tank to see which octane was used.

I doubt that the higher octane gasoline had anything to do with your greater fuel efficiency unless it happend to be ethanol free.

 

The may be a number a reasons why you saw a bit better MPG. If your van has a knock sensor it might be to sensitive and causing the ECU to pull timing on 87 Octane and not on 91. It could be as some have stated that the 91 octane you bought was 100% gasoline dispite the fact that you bought it at a cutrate outlet. Since Costco buys on the open market they may have found a deal on some better grade gas to your benefit.

Or it could have been a tail wind as someone else also mentioned.

On my DD a 2000 Contour SVT I see noticable difference in MPG when I use 87 or 93 octane fuel. Ford reccomends 91 octane fuel for the engine but in my area I can buy only 92 or 93 octane. I usually fill up with 93 and then when I get to 1/2 tank fill up with 87. I don't ever buy 89 as the cost is only $0.10 more for 93 in my area.

 

Apparently "the vast majority of stations" in USA only sell gasoline blended w/ethanol. Various sources cite over 90% of gasoline sold here contained ethanol back in 2010 & that percentage surely increased.

In FL ethanol is mandated & the only way you can buy ethanol free gasoline is via a bit of slight of hand, where you sign document saying you're not using it as an over the road motor fuel. If you're willing to go out of your way to find it. Told ethanol is mandated in NY too. Didn't see any "stations advertise" ethanol free gas traveling inbetween. If "that's certainly not the case around" your neck of the woods beware the clock is probably ticking.

Some less than "modern engines can" take advantage as well. Mid 80's SAAB 900 use knock sensor & adaptive engine management. It was the 1st I'd heard of.

Readers should also be aware that less scrupulous retailers may have another motive to "justify the ridiculous upcharge" - profit gouging. The least scrupulous have exploited ethanol bashing & don't even sell ethanol free gasoline. It is a Buyer Beware market. Note the "simple test to determine if ethanol is present".

 

The gas banners at the Costco pump looked like Shell banners minus the Shell logo. I am sure Costco buys from one of the major refineries under long term contract. They would not put there name on the product if there was a chance it was second rate.

Do the Triton motors have the capability to adapt via knock or O2 senor to higher Octane gas?