View Full Version : fuel ecconomy versus octane ...what brand is best.. which octane is best

04-01-2012, 02:46 AM
anybody compare octane ratings and fuel mileage yet.....

first tank dealer filled it up...got 34 miles per gallon.....
second tank mobil gas 91 octane 33 mpg
third tank today using Chevron 91...dont remember could be higher octane

want to know if by going to a lower octane rating will my mileage suffer

anybody have any real numbers for comparison

04-01-2012, 10:58 AM
On a trip home last year from Nashville, about 850 miles, Thad Kirk and I tried an experiment. We went home almost the same route. I used premium 92-93 and he used midgrade 89 octane. We drove at about 72-75mph on the highway following each other. In the end, after about 2 fillups, we found a difference of about 1.5 mpg between us. I was averaging about 44 mpg and he was about 42.5. We figured that economically, it wasn't worth up to 20 cents per gallon difference to get the improved fuel economy.

Fix it again Tony
04-01-2012, 05:56 PM
I'm 220 miles into a tank of premium now, I'll let you know my personal results in a few days. I don't anticipate that premium is worth the extra bucks, but I was convinced to give it a try by reading the "Real world mileage thread" on this forum. I was convinced years ago to try premium in my Kawasaki Ninja, but found it to be a waste of money. But! We shall see....

the stig
04-01-2012, 06:45 PM
My car seems to have a little more power with chevron premium. Because I don't feel I have power to spare I always run premium. I get better milage also but thats not why I run the good stuff.

04-01-2012, 09:42 PM
My car seems to have a little more power with chevron premium. Because I don't feel I have power to spare I always run premium. I get better milage also but thats not why I run the good stuff.Me neither. I didn't find much, if any, difference in mpg, however, the engine did sound like it wasn't 'laboring' as much using Premium. I switched back to Premium. Since I'm retired, it doesn't make much difference in my gas expenses. Unless I go on a road trip, I fill up about every two weeks or twice a month.The last road trip to West Palm Beach last week was 357.4 miles roundtrip and it took $37.00 to fill the tank @ $4.04 per/gal...the tank was down to the last two tiny bars when I hit Sam's Club Gas Station.

04-02-2012, 01:17 AM
I asked an engineer specifically about the octane making a difference concerning fuel economy. He said it didn't matter. So power yes, fuel economy, no.

04-02-2012, 07:16 PM
I asked an engineer specifically about the octane making a difference concerning fuel economy. He said it didn't matter. So power yes, fuel economy, no.

Thanks, thats definately good to know!

Fix it again Tony
04-05-2012, 11:33 PM
Finished my tank of Shell premium, 30 mpg exactly. Previous tanks of regular gas from 76, Chevron, Costco, all 30 mpg exactly. All city miles, in a 500 Sport manual. Doesn't seem worth the extra bucks. It might have had a slight bit more pep, or it might have been me imagining more pep.

04-06-2012, 07:37 AM
I asked an engineer specifically about the octane making a difference concerning fuel economy. He said it didn't matter. So power yes, fuel economy, no.

This is correct. Octane is more important as regards avoiding ping.

04-19-2012, 02:45 AM
but is it only about fuel economy or may better gas/93octane be better for the car overall is the real question i would like to know

04-19-2012, 05:07 AM
I have been using 91 octane gasoline (91 is max. in CA) since I bought my 500 last December. Since I got my Injen CAI, Borla exhaust and sprint booster about three months ago, the car ran amazing on premium, acceleration was noticeably faster, a blast to drive. Two weeks ago I switched to 87 octane. Huge mistake, the car ran at times as if it was on three cylinders, probably a result of my mods. I'll switch back to premium next time and stay on it. Fuel economy was about the same, 32 around town, 45 on the freeway, give or take a couple of miles per gallon. But seriously, the 500 is way too much fun. Feed your baby right!


04-19-2012, 07:14 AM
Yeah but you have bragging rights of getting almost 45 mpg. That is amazing!

04-19-2012, 02:53 PM
Yeah but you have bragging rights of getting almost 45 mpg. That is amazing!

Thanks! That's freeway driving with cruise control on at 65 mph. I know some people have gotten higher. Quite an amazing little car, fun to drive and fuel efficient.


04-19-2012, 02:56 PM
I was kissing 50 mpg with the 1.2 liter Euro model that we had a few years ago.

05-06-2012, 04:11 AM
I run shell 93 or BP 93 exclusively. For me its not so much about how much better my gas mileage is, but rather how well the car responds to the gas. I have been using only these gases in my cars for the last 3 years and have noticed that it helps them all achieve better gas mileage as well as smoother acceleration and more power. I personally think its better for the car and I don't really care if its 20 cents more per gallon, I'll take that hit to protect my car and have a lot more fun driving it. Plus, I know I get some of that back in better gas mileage. My last car, a Ford Focus, was getting 24-25 in the city until I switched to BP premium. Then it started getting 28-29 with no change in driving habits and the car felt much better. I've never used any other gas since then. I currently get about 37 mpgs delivering pizza in a fairly suburban area in my Fiat and couldn't be happier with the way it drives.

05-06-2012, 12:27 PM
i now have 1972 miles on my car. the lifetime mpg is 45.8 (actual manual calculation). mostly light suburban type driving. all on Shell 87 octane.

05-24-2012, 08:33 PM
Fuel economy and performace are two different things. This engine was designed, built and dynoed using 91 octane fuel. Just because the fuel economy figure may not net appreciable results in the pocket doesn't mean the performance won't take a noticeable hit. True - the car will run on regular, but only after retarding the timing to do so. I'll stick with premium for the insignificant difference in out of pocket. It's worth it to me to ensure the engine runs as intended. Considering an above average 20,000 mile a year - and averaging a modest 37 mpg as I do - with a $0.20 per gallon savings you would pocket just over $108.00 per year on 87 octane. Thats $9.00 per month to run a car on fuel it was not designed for from a performance perspective. Does it seem a bit rediculous yet????

05-25-2012, 10:26 AM
it is designed to "meet all emissions regulations and provide satisfactory fuel economy and performance" using 87 octane.....or higher.

per the manual: "Your vehicle is designed to meet all emission regulations and provide satisfactory fuel economy and performance when using high-quality unleaded gasoline having an octane range of 87 to 91"

i be interested to see what actual performance gains are made on 91.

05-25-2012, 11:40 AM
it is designed to "meet all emissions regulations and provide satisfactory fuel economy and performance" using 87 octane.....or higher.

per the manual: "Your vehicle is designed to meet all emission regulations and provide satisfactory fuel economy and performance when using high-quality unleaded gasoline having an octane range of 87 to 91"

i be interested to see what actual performance gains are made on 91.

"Satisfactory" being the operative word. They recommend 91 or higher for a reason. It certainly would be nice to be able to quantify the difference. For less than $10.00 a month I'll err on the side of "recommended".

05-27-2012, 08:38 AM
phillips 66. 87 octane

406.5 miles driven. 8.97 gallons used..........45.3 mpg(U.S.)

mostly light suburban/ state roads. 10% actual city.

06-11-2012, 08:07 PM
I have a Sport with a Mopar CAI , Roadrace Timing Control and a Borla system .
MPG on normal highway I can manage 36-38mpg . Through my commute ( the Cajon Pass I-15. A PITA for a small car ) I manage about 33mpg and at times 31.
All using 87 octane . I noticed absolutely ZERO difference in my MPG with the octane with the exception of the price being more . I notice only a 2 mpg difference between good gas ( brandname ) and crap gas ( no name , Arco , etc ) . My biggest help in MPG saving was the timing controller . Was it really worth $400 to save 3mpg ? Time will tell.

06-11-2012, 09:05 PM
Without reading this complete thread, I will respond although it may have been said.

Without fuel testing at a laboratory level, you will never know. I have sent several fuel samples for what is available in Hawaii. I know that 92 octane is the highest commonly available octane here with one fueling station selling 100. However, I never tested the 100. In Hawaii, on Oahu to be specific, not one sample tested measured 92. The highest was 90.8. Regular and mid grade fuel also had a lower octane than advertised. Contamination was different at every station. Many samples came back contaminated with mud, saltwater (especially stations at sea level) or a combination of the two along with many other contaminates. Based on my results, Shell fuels in Hawaii came back the highest rated and least contaminated. Chevron was second. While I cannot control variable such as humidity and air density, I ran numerous tanks of both Chevron and Shell through my BMW while attempting to maintain the same throttle inputs. Consistently, Shell outperformed Chevron by at least 2mpg per tank.

For the people on this island reading this, yes I know there are only two refineries here. Tesoro and Chevron. What is different is the additives in the fuel added after refinement. So the based product is essentially the same. The additives do in fact matter.

So, in order to answer your question you will need to have fuel samples analyzed. Then you will only have an answer pertaining to quality only. The rest is up to your driving style.

07-05-2012, 09:38 AM
Are you using Pure Gas or 10% ethanol?

08-14-2012, 01:16 PM
Just finished a road-trip, about 800 miles round trip. I used premium (91 is the highest you get in California). At Shell, its about 20 cents more than regular 87 octane. From what I've read here and on the fiat500owners forum, economy is only slightly affected if at all by higher octane. But cleaner burning of fuel with less residue is the real benefit. On my trip, I averaged about 39 or so mpg with a mix of stop n go Los Angeles traffic, climbing the mountains North of LA with Air conditioner on full blast due to the 107 degree (41C) heat outside. I easily maintained 60 mph going up 6% grade for several miles with A/C on full blast on me, my wife, and my 65 lb dog. A drop into third gear and I had Plenty of power to overtake the trucks and cars that were lagging up the steep grade... in the awful heat with A/C on. I think the premium fuel makes a difference in performance using my anecdotal example.. not real proof, but good enough for me. Filling a 10 gallon tank and spending about 20 cents per gallon more means about 2 dollars extra to keep my engine clean (keep in mind, top-tier fuel from Shell, Chevron, 76, and the other big boy fuels). I fuel up about once a week, only 8 dollars per month. That's a very minor investment into the maintenance and care of my new car, well worth it in my opinion.:peach:

03-15-2013, 04:04 PM
I have had a lot of hi-performance cars that required 91+. they didn"t run worth a darn on 87. I have found tha by using the same company gas @ 91 (shell, sunoco etc.) my mileage would level off,and best of all, my get up and go really got up and the car really gets ....I think the computer notices this and electronically sets the spark... Always use what the manual says, pick your company and stick to it for at least a month at a time to allow your engine to adjust. If you"re not happy, change to another company. My Mercedies was so picky it would spit at me if I didn't use the right gas. Then it would drop it"s gas mileage by 3mpg and would just stand there when I stomped it. So, stick with it. I'm averaging 30.2 on my Abarth. I averaged 23 mpg on my 500+hp on my Dodge super-Bee which is unheard of. Works for me.

03-15-2013, 05:42 PM
with the 500, higher octane has done nothing to improve mileage over 16,000 miles, and I track my mpg's pretty religiously. I don't notice any noticeable performance boost with higher octane, either. maybe I would notice with a high performance model, but Fiat hasn't brought one to N. America yet.

03-16-2013, 12:21 PM
When I first met with a group of Fiat engineers a few years back for an informal tour of the new 500, we were all talking about various aspects of the car, one of the production engineers asked the engineer in charge of the motor what fuel the car was rated on, and the answer was premium. It makes a difference in the power, it may not be appreciable in certain operating conditions, but it is there. So if you aren't pushing the motor where octane would make a difference, you probably aren't gaining anything from using premium, other than a different additive package. The harder you use the engine (heavy throttle, fast acceleration, etc.) the more octane will matter.

And just to reiterate what I said earlier in the thread, I did ask the engineer who knows about this and he told me octane doesn't effect the mileage in the 500.

On a personal note, on any of my cars with a knock sensor, I run 93 octane premium. Mainly for the added performance and cleaning additives. However, one of my cars has a lot of miles on it and I don't accelerate hard with it, so I dialed back to regular or 91 octane.

04-10-2013, 03:20 PM
octane doesn't make power, it is detonation resistance which is required on high compression engines. it's not octane that makes power, it's that powerful engines may need octane. generally low octane fuel has a higher heat output (though it's slight) so run as low as the engine is happy with for power and economy.. also avoid fuel with high ethanol/methanol content. nothing sucks heat out of the combustion better than alcohol which may absorb water. alcohol is also hell on engines as far as corrosion and lubrication goes.

04-10-2013, 06:40 PM
I've only ran 92 octance in my abarth and am averaging 26.6 mpg. I would say my driving is 90% city and 10% hwy. A lighter right foot would help me alot. Ha. Octane doesnt change mpg, it will just cause the car to pull back timing if your running lower octane than what the car is tuned too. This is what will decrease your mpg because the car now has to work harder because the motor isn't producing as much power. I almost always use Shell in my cars and if I'm unable to I use another top tier brand. My cousin used to not think that it mattered until the injectors in his BMW got clogged with sediment from cheap gas. What I recommend to everyone I know is to use the best brand of gas for your car at the correct octane level. If you use one level lower in octance for your car (~15 cents cheaper) and drive 15k miles a year it saves you about $100. IMO its not worth it and becomes a wash when you factor that your car has to work a little harder and will lose probably 1mpg.

04-10-2013, 08:58 PM
uhhh, errr, sorta, but if the timing needs to be kicked back i assure you it effects gas millage in a very negative way. i said run as low as the car is happy with, i should qualify that with no lower than than factory recommends should it effect timing and millage because not all drivers may notice if the engine actually likes it.
when the timing is retarded the fuel has less time to burn and do work against the piston and may still be burning when it enters the exhaust contributing to engine heat that isn't converted into usable power.

a nice product would be a knock sensor readout so you know if the fuel is working for you or against you. like a light that lights up whenever the timing is under a knock related retard condition.

also this whole light right foot thing people talk about may not be the answer. the energy it takes to acelerate an object depends only on what speed you accelerate it to. not how long it takes if i remember my physics right. driving easy only prolongs the time the engine is in an inefficient state and keeps you in low gears longer. don't rev the engine in excess, i shift around 3000-3500rpm untill i get up to speed then just skip to 5th or 6th and get 32mpg around town in my dart, don't be afraid to put your foot down 50%-75% unless your speed is dictated by stop signs and traffic lights when it is best to just never hit any appreciable speed because you will just have to stop and waist all that precious energy you just put into the car..

engines have the lowest bsfc under high load. means it does more work for the fuel consumed. that means loading the engine accelerates you or maintains your speed more efficiently. basically that says to use the gas pedal but also use higher gears as long as the engine is still able to accelerate the car. just avoid over 75% throttle where many cars will go into WOT mode which runs an open loop and is calibrated for a richer mixture as a safety factor, and to make a bit more power. and avoid such heavy loads (or low octane fuels) that the timing has to retard excessively. another thing you may notice is the engine is very efficient at torque peak. it really never out does upshifting as far as millage but you might find the car has a sweat spot in high gear at a surprisingly high speed. i seem to get better millage at 75mph than at 65 but not as good as 45-50mph. hard to tell though my commute has a lot of hills.

04-10-2013, 09:07 PM
uhhh, errr, sorta, but if the timing needs to be kicked back i assure you it effects gas millage in a very negative way

what dart1.4t said... I mean if you don't (as the driver) compensate for the lower power (however much that might be or not) then maybe you would see no difference but I know that if X amount of pedal application wasn't giving me the acceleration I was expecting, I'd press harder and use more gas etc... so maybe not in the 'all things being equal case' would octane impact mpg but I bet real world it does for some drivers. Seen it other cars fwiw..

04-11-2013, 07:27 PM
even if you don't step on the gas harder it effects the mileage. if it effects the power it effects your speed, if you go slower you go less distance. distance is a factor in "mileage" as your speed drops (or fails to increase at the rate you wish) yes the engine speed and fuel usage drops but it doesn't drop as much as the rpm drops because cylinder pressure goes up further, more knock, more retard, more lost power, more lack of acceleration more loss of distance....

it all becomes convoluted with drive by wire throttle and computer controlled turbochargers, you cant' know what the computer is doing for you. drive by wire isn't used to just put the throttle blade where your foot is, if it was that simple they wouldn't spend the money to replace a cheap cable with servos and encoders or add a solenoid to the waste gate if they didn't have some extra function in mind. drive by wire is sometimes used for traction control and sometimes it also does driver commanded torque or acceleration. you put the throttle down say 50% and the the computer tries to create up to 50% of the peak torque (though it doesn't have to be linear) for as much of the power band as possible till the engine hits an rpm that is programmed for that throttle position. the throttle blade and waste gate move to where they have to make the intake pressure that is mapped to that engine speed and throttle position. factor in variable valve timing and things get really complicated. it's impossible for me to know exactly what decisions the fiat engineers made in handling timing and pressure.

any time the timing retards due to knock the exhaust heats up, when heat goes out the exhaust it's not moving the pistons, means fuel is burning but it's not moving you. that can even be avoided with drive by wire throttle and variable valve timing if the consideration is taken by kicking back the boost and throttle angle, opening the intake earlier to add some reversion to act as egr to cool combustion (does this engine have an external egr system? might not need one) but even then there is a small effect on mileage because lower intake pressures and cooler burning have higher bsfc (brake specific fuel consumption)

that said i'm not sure how much 87 will hurt the 500, the dart with the same engine is rated to pass epa with 87 but the sticker says 91 because it is needed for maximum power so i think for everyday driving especially on a smaller car than the dart 87 is likely fine. 91 would be for when you put the pedal to the floor.

edit: i guess what it all means is ymmv. generally cheap gas actually has higher heat output but if the engine and driver work better together with premium it likely far outweighs any extra btu's the low octane gas might have.