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The Premium Fuel Better Mileage Controversy

47K views 126 replies 49 participants last post by  Merc6 
#1 ·
Ran 2 tanks each with both 91 and 87 just for trial and I get absolutely NO change in fuel mileage. At all. Slightly smoother performance with Premium, but nothing really to warrant the extra cost. I use Sunoco since its the only decently tiered gasoline near my home. However here in college I have access to both Exxon and Shell and switched to them since they are top tier. Either way, octane rating has caused no difference for me at all. Anyone's thoughts on this?
 
#2 ·
It won't change mileage for the most part. Higher octane burns cleaner and slower which reduces your chance of knock or detonation. In our turbo version regular also lowers boost levels and timing to adjust for the lower octane. Just spend the extra 2$ at the pump.
 
#3 ·
Most places where I'm from don't sell 91. Its only 87, 89, 93.. and if I'm using top tier gas it has all the same additives is what I'm told. But yeah the difference is pretty huge price wise between 87 and 93, and even 89 is some $.12 more expensive per gallon and does 2 octane make that much of a difference?
 
#4 ·
Most places where I'm from don't sell 91. Its only 87, 89, 93.. and if I'm using top tier gas it has all the same additives is what I'm told. But yeah the difference is pretty huge price wise between 87 and 93, and even 89 is some $.12 more expensive per gallon and does 2 octane make that much of a difference?
use 93 octane then. our cars are global cars and in most other countries 93 octane is the standard. the difference between 87 and 89 wont make too much of a difference. but between 87 and 93 is huge. my girlfriend put gas in my car and accidentally put in 87. I knew immediately without her telling me. needless to say i pumped that ish out and my dad got 10 gallons of free gas. And being top tier is good and all but there is still differences in the detergents they use. I use Chevron only. Always have and always will. In the long run it wont hurt anything but performance. BUT... if you start looking at a tune for your car you can only run 91+...just something to think about.
 
#21 ·
Did GM give a threshold for "Really Hot"?
I consider it really hot in NC when we top about 93 degrees.
I'm sure in more northern locales, 80 degrees + might be considered really hot.

Just sayin'....we need to quantitatively define "really hot"...understanding that the engine bay has an environment to itself as well...
 
#6 ·
I usually use Shell or Exxon as there is no Chevron here. I have only filled up once my initial impression is that coming from 87 that the dealer put in there is a NOTICEABLE difference in the smoothness of power delivery, but I pay attention to the details like this.

Like others said it is more or less a preference because of sensors and other technological advances. However running high compression or on boosted vehicles (which have high effective compression because of turbo/supercharger) the higher octane reduces detonation which results in smoother uninterrupted power.
 
#7 ·
Sorry to hear of your findings.

However, 93 for me has proven to be worth the $2 more per fill. I dont think I'd been able to achieve 49.2 mpg over a tank with 87... and the added performance is a plus!

I'd try 93 at several different locations. I've experienced 93 octane in some Mobil stations that I'd bet was not in fact 93 as my data logging (using Diablo Predator on my SRT8) indicated short term spark retard when it should not have.

Shop around and report back! :)
 
#8 ·
I've always ran 89 vs 87 because certain days of the week they price it the same at my local station. Since the weather has cooled off I've achieved over 50mpg average w no a/c on and driving 55mph :) 40psi in the tires
 
#9 ·
Shell and Exxon were two stations I actively avoided when living in South Carolina. They always seemed to have the worst quality gas, and the dirtiest stations.

My best 2 tanks so far have been on 93 octane.
 
#10 ·
boycotting Exxon-Mobil since 1989, BP since 2010.
 
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#12 ·
boycotting Exxon-Mobil since 1989, BP since 2010.

Just curious, why are you boycotting?
Just because of several accident's, or some other reason? - Dan
 
#14 ·
I'm gonna be trying out 93 octane starting next fill up, hoping that the slower burn means the gas'll last a little longer as well. Now to choose a place, I'm thinking Valero or HEB, shell is by my office, but I prefer close to ome, which is exxon, valero or HEB.
 
#18 ·
It has a turbo, run premium. I dont care what people see fuel economy wise, relying on a knock sensor to pull timing to get it to stop detonating is not a safe smart practice. If you plan on keeping the car past the warranty run the right gas in it.

Detonation is equivalent of striking the piston with a hammer on its way up, eventually that is going to cause a problem. Even if the knock sensor picks it up quick and retards the timing it still happened. And then after its ran for a while or has been shut off and re started it will try normal timing again until it picks up more detonation. Run premium and kiss detonation goodbye. I would like to bet that an eco engine ran on 87 will need rebuilt in half the time of one with premium. Ive been messing with turbo engines for a long time (almost 10 years) and I have never EVER heard of running one on 87 until joining this forum:question:

If your not willing to pay the extra money for the higher grade fuel then dont buy a turbo car. Why do you think its even at the pump for? Some cars need it, and this is one of them.

Do some of you guys think its just for bmws, or people with too much money just decide to run premium because they enjoy wiping their ass with money?
 
#19 ·
For what it's worth, shop around and try various stations. I don't think the "brand" always means the best.

My best tanks so far are achieved using (insert gut laugh here) Kroger 93 octane! I was using Costco previously.

Still crossing my fingers to get 50 mpg out of this week's commute tank. It's close!
 
#20 ·
For what it's worth, shop around and try various stations. I don't think the "brand" always means the best.

My best tanks so far are achieved using (insert gut laugh here) Kroger 93 octane! I was using Costco previously.

Still crossing my fingers to get 50 mpg out of this week's commute tank. It's close!

Costco is going to be my best bet for premium 93...I think I'll full up on it today on the way home and see what happens.
 
#22 ·
I cant wait to take my car to visit my relatives in Illinois to see what it gets there. Every car I have owned has got 5mpg or better vs down here in tennessee. Our common speed limits here in the part of tennessee I live in are 40 in town but with lots of traffic lights. 40 can get great instant milage, but having to stop and get back up to 40 kills it.
55-65 on hwys but all the hills kill it. And 70 on the interstate but the hills once again kill it.

In illinios it is so flat and 55 is the highest speed limit (in the area Im from) you will see on hwys. In town (in decatur) there are minimal lights that let you get through town easially at 50mph and you turn off to side roads to turn into the businesses usually. Kinda like a slow mini freeway. Like I said I got better economy by over 5mpg in my dodge ram and my lifted pathfinder which both got terrible milage. I would expect about 50mpg out of my cruze up there and im excited to plan a trip there soon to see what I can get out of this thing. I average right at 39 here in tennessee.
 
#24 ·
I gave a couple tanks of 93 a try over 87. There was a slight difference in MPG and the car seemed to like it better. Otherwise, it's not very noticeable. Could be the 100º+ heat. I'll give it another shot here this Fall and see how she does.
 
#29 ·
If the 91 is no eth then you will c a bump in mpg, but if it has eth in it then you prob wont see a difference in mpg (but it will prolly feel a lot smoother with the 91). My best tank is 54.0 and that was with 87 but no eth. Few months ago I tried a tank on 91 but it was 10%eth, and I did not see a difference in mpg ( I had been runnin 87 10% eth at the time, now 87 100% gas)

Just my $.02
 
#30 ·
I will start by saying that i only run Sunoco in my vehicles, c'mon its the official fuel of NASCAR !! LOL anyways, when i first got the car i ran only 93. Now that i have started to use it to commute to work i cheap out and go 87. I agree that there is a noticeable difference in performance and ride quality with the grades. I honestly have become used to it and have now been reminded to go back to 93!

Has anyone tried any octane boost products?
 
#31 ·
I will start by saying that i only run Sunoco in my vehicles, c'mon its the official fuel of NASCAR !! LOL anyways, when i first got the car i ran only 93. Now that i have started to use it to commute to work i cheap out and go 87. I agree that there is a noticeable difference in performance and ride quality with the grades. I honestly have become used to it and have now been reminded to go back to 93!

Has anyone tried any octane boost products?
when I first purchased my car my dealership sent me a customer survey that gets sent to GM. They told me if I fill out and bring it back they will fill it up with gas. So I skillfully drained that bish down to 'E' and barely made it there LOL. They filled up with regular of course which I was prepared for. I used 3/4 bottle of the NOS brand octane booster. Might have been a placebo thing but it felt like I was running premium to me.
 
#34 ·
There is eth free gas, but there is no such thing as 100% gas (that is 87 test or higher)

There has always had to be additives in order to get it there. It used to be lead, when it stopped being lead it started being other things.

With that said, your economy will lower with ethanol on any vehicle that corrects air fuel ratio with o2 sensors.

ethanol is not bad for engines though. It is better than methanol, toluene, acetone and other things they use. If they were required to provide a detailed list of what all is added into the gas like they are with ethanol you guys would be driving around looking for the stations that only have ethanol. The real only problems with ethanol is when stations dont have good tanks and dont maintain them properly. Anything that allows water to get in or if you or your car store fuel in a way that lets moisture in.

Ethanol will help keep your fuel system clean, combustion chamber clean, valves clean ect. Now I say it helps because it cant keep up when the other 90% is gas.

Here is a picture of some pistons that were ran on e85 (85% ethanol) for 3.5 years. It was a turbocharged 2.0 4cyl and only ran on a gas base tune for engine break in for around 1 month or less. After tuning it made over 400whp.
This is what they looked like when it was taken apart.



Its just funny to me that people run away from ethanol.
 
#35 ·
K two questions:

1) Is pure gas better for your car as a whole or just better for fuel mileage? I peeped the site and there is a pure gas station just 2 miles from my permanent residence! (I'm in college now). And as a bonus, the gas is 91 octane!

2) If you fill up say a full tank of 93 and use half of it and fill the other half with 89, do the knock sensors calculate that as 91 because of the mixture or the 89 thats in there?
 
#36 ·
Octane booster is worthless. If it says 10 points of octane, that's 0.1 octane. So your $13 bottle of octane boost that claims 60 points, or 6 octane, would take a tank of 87 octane to 93 octane. The cost difference between a tank of 87 octane and 93 octane for me is $1 per tank. Totally not worth it.

Even if you're at the track with half a tank of 93 and want higher octane, throwing in a gallon of unleaded 110 octane race gas is still cheaper and more effective than a bottle of octane boost.

The knock sensors will see half a tank of 93 and half a tank of 89 as 91, assuming it's truly 6 gallons of each.
 
#37 ·
relying on knock sensors is such a stupid idea. Look up how bad detonation is to an engine. It is the leading cause for blown headgaskets, crack rings and ringlands, bent rods and beading bearings. If your knock sensor hears detenation it will retard timing and most likely add fuel in order to try to make the 87 your using not FURTHER DAMAGE your engine. Allowing it to cause the first bit of damage is ignorant. I would only use 87 if I were leasing the car or renting it.

Ethanol is a detonation suppressor as well. I feel sorry for the poor little 1.4s that have to suffer by the guys that only fill up with no ethanol 87 because someone just as uninformed as they posted something on a forum saying its ok. Its a shame GM said its ok to run 87 for marketing reasons. Sure warrenty will cover the car under warrenty but what happens after. When you have to replace the headgasket and find what terrible shape the engine is in when you pull the head. Your ultimatly going to be paying the bill.
 
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