Premium 91 Octane...

Status
Not open for further replies.
Joined
Apr 24, 2007
Messages
4,038
Location
WI.
I've heard enough, 'If your engine spec is 87 octane fuel there is no benefit to premium 91' 'waist of money'

Why do my 2.4's run stronger on 91?

Why do I achieve 2-3 more mpg.?
 
Placebo effect?
You drive differently?

Who knows. Some engines can benefit from a higher AKI fuel. Perhaps the 204k mile example does better as the higher AKI fuel helps with deposits in the combustion chamber.

It would be interesting to see if it really helps when you don't know which fuel is in the vehicle.

Or it could be your driving style.

Without more data and true scientific examination, it could simply be other facts are in play.

For example, you could only buy 91 AKI on long trips. You use 87 around town, but when you take trips, you buy 91 and you observe better economy. Not because of the fuel, but because you are doing hundreds of miles of highway driving with few stops.

So without knowing other details, we can't determine if the key variable is the fuel AKI or
 
I don't notice a mileage difference, but my 2.4 absolutely runs better on Premium fuel (93 here). It sometimes pings ever so lightly on up-shifts from 3rd to 4th on tip-in when using 87. Hyundai checked for codes at my request and could find none, advising that the slight ping is normal as well, no issue what-so-ever. Just a result of tunning the vehicles to edge of advanced timing to eek out every ounce of mpg. But mine is also 'blessed' with very high compression ratio and GDi.
 
I find the pinging to disappear in my Chevy 5.3L V8 when in the upper RPM range when I ran 91 octane in a couple of fillups. Does the truck see upper RPM operation let alone revving above 2000RPM's? Nope, well maybe when I want to pass someone and the RPM's jump from <2000RPMs to 4500RPMs and hums up to 5600RPMs as the trans jump from 4th to 2nd gear. 87 octane is alright for this porky engine.
 
Last edited:
There's been at least two, maybe three long threads on this in the past few months. No disrespect but maybe if you read those threads you will find the answer you are looking for rather than going over the same ground - again.
 
Originally Posted By: dblshock
I've heard enough, 'If your engine spec is 87 octane fuel there is no benefit to premium 91' 'waist of money'

Why do my 2.4's run stronger on 91?

Why do I achieve 2-3 more mpg.?


There's probably something wrong with your car.

The BTU content of regular and super is about the same, some actually say super has less.

If there's carbon buildup or whatever in your car and the system is retarding the timing, then you will see slightly better gas mileage and performance. However if the engine has not had the timing retarded there should be no benefit to running super instead of regular.
 
A lot of engines will advance timing until their knock sensors detect knock, then retard timing slightly. Higher octane will allow for greater advance and a different feel to the engine. The same engine can have a certain HP rating in a lower range of vehicles that are sold as using regular fuel (toyota 3.5 V6 comes to mind) and the exact same engine is spec'd with a higher HP rating in the lux market on premium fuel(same engine in a lexus LS350 for a number of years...not sure now).

Both owners manuals stated the same thing in different ways:
Lexus - premium fuel recommended but regular fuel allowed if premium was unavailable.
Toyota - regular fuel recommended but premium fuel may provide performance gains.
 
Last edited:
Originally Posted By: dblshock
I've heard enough, 'If your engine spec is 87 octane fuel there is no benefit to premium 91' 'waist of money'

Why do my 2.4's run stronger on 91?

Why do I achieve 2-3 more mpg.?


Running premium in an engine that only needs 87 is a "waste of money".

As far as "run stronger" that is totally in your head.

As far as 2-3 MPGs, there is a bad calculation somewhere.

Trust me, if automakers could achieve 2-3 more MPGs just by upping the octane, they would do it.
 
Originally Posted By: wemay
I don't notice a mileage difference, but my 2.4 absolutely runs better on Premium fuel (93 here). It sometimes pings ever so lightly on up-shifts from 3rd to 4th on tip-in when using 87. Hyundai checked for codes at my request and could find none, advising that the slight ping is normal as well, no issue what-so-ever. Just a result of tunning the vehicles to edge of advanced timing to eek out every ounce of mpg. But mine is also 'blessed' with very high compression ratio and GDi.


If your 2014 vehicle is pinging, something is wrong.

Originally Posted By: Wolf359
Originally Posted By: dblshock
I've heard enough, 'If your engine spec is 87 octane fuel there is no benefit to premium 91' 'waist of money'

Why do my 2.4's run stronger on 91?

Why do I achieve 2-3 more mpg.?


There's probably something wrong with your car.

The BTU content of regular and super is about the same, some actually say super has less.

If there's carbon buildup or whatever in your car and the system is retarding the timing, then you will see slightly better gas mileage and performance. However if the engine has not had the timing retarded there should be no benefit to running super instead of regular.


Premium gas has less energy that regular gas. The combustion inhibitor takes up space and does not provide energy.

Originally Posted By: wirelessF
I find the pinging to disappear in my Chevy 5.3L V8 when in the upper RPM range when I ran 91 octane in a couple of fillups. Does the truck see upper RPM operation let alone revving above 2000RPM's? Nope, well maybe when I want to pass someone and the RPM's jump from div>


My 5.3L acted no differently when I ran a couple of tanks of 93. The mileage remained about the same and engine sounded the same.
 
For engines require Premium you will loose some power at higher RPM when using regular, especially when ambient temperature is above 100-120F.

My LS400 didn't have problem accelerating while climbing steep hills outside Death Valley in summer to Vegas, the ambient temp was in mid 120F, same hills same temp with 87 the LS400 couldn't rev pass 3000-3500 PM. But it didn't have problem accelerating on those hills, when we went to Vegas in winter months with temperature below 60-70F.
 
Originally Posted By: tcp71
A lot of engines will advance timing until their knock sensors detect knock, then retard timing slightly. Higher octane will allow for greater advance and a different feel to the engine. The same engine can have a certain HP rating in a lower range of vehicles that are sold as using regular fuel (toyota 3.5 V6 comes to mind) and the exact same engine is spec'd with a higher HP rating in the lux market on premium fuel(same engine in a lexus LS350 for a number of years...not sure now).

Both owners manuals stated the same thing in different ways:
Lexus - premium fuel recommended but regular fuel allowed if premium was unavailable.
Toyota - regular fuel recommended but premium fuel may provide performance gains.


As I've mentioned before, I worked on the electronics end of such a knock detection system over 20 years ago at a supplier to one of the Big 3. The levels of knock that could be detected were far below what a driver could hear or feel...as we understood it, the idea was to run the car in very light knock (non-damaging) whenever possible.
It was impressive to watch the system in action on a dyno. And, this was a long time ago...any reasonably modern gasoline powered car from a major manufacturer should have a similar, and probably far more capable, system.
 
Originally Posted By: stchman

...there's probably something wrong with your car


Being the owner, only i could hear it, it's so faint and fleeting unless i point it out. But having visited two dealerships and getting the same answer ("not to worry at all"), not to mention hearing the same thing from HyundaiUSA Tech, I'm fine with having everything documented in the event it gets worse.

Having experienced this, i can very well believe the OP's experience regarding a slight difference in drive characteristics. The mpg difference? Not so sure.
 
Originally Posted By: stchman
The combustion inhibitor takes up space and does not provide energy.


I want to hear about this "combustion inhibitor". Is he related to the "fun governor"?

He just "takes up space"? Like a slacker roommate who never has his share of the rent, but always has good weed?
 
Originally Posted By: stchman
Originally Posted By: wirelessF
I find the pinging to disappear in my Chevy 5.3L V8 when in the upper RPM range when I ran 91 octane in a couple of fillups. Does the truck see upper RPM operation let alone revving above 2000RPM's? Nope, well maybe when I want to pass someone and the RPM's jump from div>


My 5.3L acted no differently when I ran a couple of tanks of 93. The mileage remained about the same and engine sounded the same.


wirelessF, I'm glad to hear that about the high RPM ping, for my sake if not for yours. My 2001 has had a high-RPM spark knock since new. "Normal" according to the dealers I took it to.

My experience with a Chevy 5.3 is that premium does make a noticeable difference in low-rpm responsiveness. It also reduces the high-rpm ping. I haven't used 93 consistently enough to track mileage. I just use the cheaper stuff and keep my foot out of it.

Using the Torque app, I have verified less knock retard under normal driving conditions with 93 octane, and a little less with 89 compared to 87. I'm not sure if that means the vehicle is programmed to increase advance with higher octane, or just that less ping makes it pull less timing. I'll have to watch both advance and KR next time.
 
if the timming is allowed to advance with higher octane wouldn't that explain the better performance?
 
I have owned a HHR with a 2.4 a chevy cruze with a 1.4 turbo and a malibu with a DI 2.4. I have had 2 people who are trained GM factory technicians that the cars computers are open to higher octane fuel and you will see a performance benefit that is measurable . That said I too had measurable differences with premium fuel in both acceleration and MPG and use it today . IMO throttle response in these 4 cylinder engines with regular fuel is criminal .
 
Originally Posted By: dblshock
if the timming is allowed to advance with higher octane wouldn't that explain the better performance?


I guess this is the question I would have, if the engine can adjust to the fuel used it makes sense that it could be different
 
More timing advance can give better results. I had a 1979 Ford F150 with a 6 cyl engine, it pinged. I played with the timing and the adjustable advance on the distributer and I found that premium gas gave more power and better mpgs. Doing the math the cost per mile was less with premium gas.
 
Can someone tell me what a "waist of money" is?

Is that one of those belts you conceal gold coins in?


Some cars will run better with premium Esp during summer or while towing etc.

They are detuned with a knock sensor because as you know requiring premium is a buzzkill to buyers.

So when using higher octane fuel they can sometimes have better performance. Also some places premium fuel has no ethanol... here(Northeast Ohio) it has more.
 
Status
Not open for further replies.
Back
Top