python

iTrader: (4)

wow...that's just not true...any of it. show me a link that proves this cuz ill show u 10 that disprove it.

PureDrifter

iTrader: (10)

yeah no.

less power =/= less mpg. go do the same highway loop with a tank of 87 and a tank of 91. the difference in mpg will be statistically insignificant. as evidenced by the past 17 pages + of thisthread.

peterls

That would be like saying we can eat whatever we want, because when we sleep we really don't use much energy...

No one drives highway loops. Most people drive in city traffic, with constant stops and goes. Even on a highway, there are uphills, bad traffic, passing, merging, all situations where one needs power.

here is one study that proves that for each 1 point increase in octane rating, on average, there is an increase in fuel efficiency of about 1%:

http://papers.sae.org/2013-01-2614/

So between 87 and 91 octane rating, the difference is about 4% and an engine that produces less pollution. Now the only thing left to decide is whether your local gas station sells premium gas for more than 4% difference in price...

To make a claim that using lower octane fuel in a higher octane rated engine is somehow better or competely equal is absurd. We may only argue to what extent can one do it without worrying too much, just as we could argue that eating junk food from time to time will not really kill anyone. But eating junk food every day for ever, will certainly have its costs, even if in the short term (and short term both for food and octane rating could be 10 years), there seems to be no difference.

ps I am fully aware that there may be situations such as at higher altitudes where lower octane rating actually makes sense, but very few of us live in the Rockies. By the same token, we could argue that there are also many situations where using higher octane rating benefits the car especially when exposed to higher loads.

peterls

Here is another interesting study about influence of octane rating on fuel consumption:

http://www.greencarcongress.com/2014...0424-chow.html

python

iTrader: (4)

wow..here we go again..
http://www.csmonitor.com/Business/In...as-saving-tips
ive already tested this for 8 years running as I have relatives who live 650 miles away..1300 miles round trip and have used 87..89..91 round trip. and I avg 23 mpg. with any and all grades of gas. I travel the same route..same speeds..same tires..same air pressure and the only variance is the weight in the car..only by 50-100 lbs. u will have more of a negative affect by having the wrong air pressure in ur tires then u will using 87 gas for mileage purposes..higher octane does NOT PRODUCE better mileage,other wise u can just get octane booster in a bottle and get great mpg. if u think im wrong then put 87 in ur tank and go on a road trip. then go on the same road trip and use octane booster that is 104. I don't use 87 octane in my car but I know darn well using 91 doesn't produce better mileage.

peterls

Python, you'd be surprised but I absolutely agree with you.
The question is not so much "what MPG do I get in a-typical condition" (such as constant highway speeds), but whether in general it is better or just the same or at least a little imprudent to run lower octane gas in our engines which were designed for higher octane gas.
I agree that provided there is minimal load on the engine, such as at constant highway speeds, or at higher elevations, or on downhills, it does not really matter, you get nothing, and may even loose something by running higher octane gas.
BUT!
That is not a typical driving scenario.
We drive mostly in cities, and even in smaller places or rural places, you still have lots of stops and goes and other things which all increase load on the engine and either reduce your mpg (depending on the load - from nothing where there is no load, to something like 4% in an average load situation), or in the worst case, increase pollution, dicrease engine efficiency and perhaps produce an odd knock or two and potentially damage the engine.
And as far as I know, knock sensors work by first sensing a knock, so only AFTER the knock has already happened (which is really a detonation), will the ECU adjust ignition timing to compensate for lower octane rating.

sha4000

iTrader: (1)

Well I've been driving an LS for 18 years and have done so many long road trips that I can weigh in just a Lil on the subject. On the Highway from full up to empty I've used all grades and get roughly the same mpg. I've Run the tank to the display just says low fuel on my 98 and with the light on for many miles in my 91 to test my theory. Now put me in city traffic and the mpg suffers with the 87 and is definitely better with premium. This subject has been beat to death in this thread alone.

RA40

iTrader: (6)

Yup, has been beaten. So for the owner if running 87 makes them happy, then it makes them happy. We all have certain preferences for our rides and that is fine.

Caniac14

I run what Lexus says it should run. I don't see why they would tell you to run premium unleaded for no reason. Besides, shell v-power is the SHEITT! All my cars have seemed to run way better on shell v-power than other random stations premium as well. So I haven't used anything but shell v-power for over a year now.

I remember I wasn't close to a shell once and my gas light was on, so I put 3 gallons of some random stations premium in my old boosted 400whp toyota, and it misfired sputtered and ran like poop randomly for a week until I put shell v-power back in. It was misfiring when I pulled into the station with about 1/8 tank left. I filled her up entirely with v-power, and she cranked right up and purred like she was supposed to.

RA40

iTrader: (6)

Shell V-Power is also suggested for Ferarri. A Porsche buddy runs exclusively Shell or if he can find non-ethanol fuels he goes with those. I like how V-Power runs in ours and have been filling with that 99% of the time for the past 12 years. Have put Costco, Chevron, Texaco, Arco and a few strays to test early on. To my perceptions, Shell did the best. Hits 390-400 mile range with 5 gallons left in the tank on an all highway run. Nearly same as when it had the stock wheels.

timmy0tool

iTrader: (7)

hmm gotta try shell. been loyal to chevron and 76 for a good while so it's worth a shot. 91 of course !

Caniac14

Yeah I pretty much run Shell 99% as well. I only run something else if I have top put a gallon or two in to get me to a shell. About non-ethanol. What are the benefits of running that? And what octane would I buy if I put in non-ethanol. A relative of mine owns a gas station/tire shop that sells non-ethanol fuel.

Need4Speed

91 octane on all my cars

python

iTrader: (4)

I was under the impression chevron was the best...ill have to try shell as well.

RA40

iTrader: (6)

Plenty of reading online about ethanol as an additive in fuels. My short take:

Allegedly to reduce CO2 emissions at a "slight" reduction of performance. It is also reduces the refinery pollutants per barrel in the production of petro based auto fuels. In the car there is something like an 6-10% loss in performance. Over time the gas heads have discovered that loss in performance to yield more frequent fill-up's. That negated what ethanol was supposed reduce in car emissions. As far as the refinery side, I don't know. There has been much debate that I don't keep up with. I can't do anything about fuel since the common ones available contain ethanol.

There have been issues on older autos where the alcohol-ethanol compounds degrade the fuel lines or in other words damage vinyl-rubber hoses and other plastic parts in the fuel supply. None of us should have any fuel supply related issues with ethanol. This could be more of a concern with autos manufactured pre-85. Ethanol is hygroscopic-absorbs water.

I ran some fuels that didn't have ethanol and my best was about 27.X MPG. With ethanol, I get no more than 26.2 some odd on premium 91. As they say, YMMV. Not like one can hyper mile an LS400 but there are times getting the good MPG is desired.