Switching to Premium gasoline

[melk]

Guess I’m spoiled with 93 at the pump here in the Southeast. I feed it to the Northstar DTS because my butt dyno tells me it feels smoother and also verifiably turns in 25 mpg highway cruising. Everything else swills 87 no problem.

 

[CDNozzle]

Doesn't the owner's manual recommend 87? If so, there will be as you say, no difference whatsoever. I get we cannot break the chains that bind, so many equate octane with "goodness" and "how much they care about their engines." This type of thinking permeates almost every aspect of life. If I spend $1400 on ice skates, I will have a distinct advantage over someone who only spent $600. You will. That is if you have the skills to utilize the marginal benefit of the design that went into the more expensive skates.

Just as if the engineers designed an engine for 91+, it will benefit from the higher octane. If they designed it for 87, the 91 or 93 is simply burned out the tailpipe with nary any benefit.

Kinda like when McDonald's came out with a 1/3 lb burger, but people still flocked to the 1/4-pounder b/c they thought it was bigger .

Octane directly has minimal to zero difference on the performance of an engine that doesn't require it (except for advancing the timing for efficiency), however [for TT fuels] the octane # is correlated with amount of good additives which benefit over the long term.

 

[rstcso]

Octane directly has minimal to zero difference on the performance of an engine that doesn't require it (except for advancing the timing for efficiency), however [for TT fuels] the octane # is correlated with amount of good additives which benefit over the long term.

Per AAA article: "TOP TIER certification mandates these additives are used in all fuel grades at all retail locations in the U.S. and Canada."

This is not so say stations can't have more than the required additive to meet the Top Tier standards, but if they agree to the TT standard, all grades must have the minimum amounts.

I ran Shell V-Power Nitro+ 93 the past several years because I perceived it to be "the best" in my area. Still believe this. They are also a TT station.

 

[burbguy82]

"Premium Only" is behind the fill door of my 09 LX570.......3urfe engine

 

[silversport]

I don't believe there is much benefit to running premium gasoline in an engine that seemingly at least cannot take advantage of the higher octane...but I am willing to learn different...

Cars that I always used premium in 2001 Corvette, 2006 GTO, 2007 CLK350 Cabriolet, 2015 SS sedan, 2016 CTS V-Sport...owners manual had either required or recommended and that's what I'd use...

original owners manual for GF's bought new 2013 Malibu 2.0T had 87 octane as what to use (later versions of the OM recommended premium) and for about 6 months this is what was used...when I learned newer owners manuals recommended 91/93 I switched her car to this and found the car ran better and fuel economy went up about 4 MPG...it has remained so and she still has this car in 2025...

I have a 2025 Subaru Outback Touring XT with the 2.4T and it is recommended to run 87 octane (unless towing to reduce engine overheat) and this is what I run currently in it...on the Outback Forum I don't see where anyone uses premium in their 6th Gen Outback XT unless towing as recommended in the owners manual...those that have tried it claim they saw no benefit (although there might be using instruments as some here have shared) to using 91/93...

some say all turbos should get premium others say it's a waste...it can be confusing to the consumer/vehicle owner...

Bill

 

[TiGeo]

I don't believe there is much benefit to running premium gasoline in an engine that seemingly at least cannot take advantage of the higher octane...but I am willing to learn different...

Cars that I always used premium in 2001 Corvette, 2006 GTO, 2007 CLK350 Cabriolet, 2015 SS sedan, 2016 CTS V-Sport...owners manual had either required or recommended and that's what I'd use...

original owners manual for GF's bought new 2013 Malibu 2.0T had 87 octane as what to use (later versions of the OM recommended premium) and for about 6 months this is what was used...when I learned newer owners manuals recommended 91/93 I switched her car to this and found the car ran better and fuel economy went up about 4 MPG...it has remained so and she still has this car in 2025...

I have a 2025 Subaru Outback Touring XT with the 2.4T and it is recommended to run 87 octane (unless towing to reduce engine overheat) and this is what I run currently in it...on the Outback Forum I don't see where anyone uses premium in their 6th Gen Outback XT unless towing as recommended in the owners manual...those that have tried it claim they saw no benefit (although there might be using instruments as some here have shared) to using 91/93...

some say all turbos should get premium others say it's a waste...it can be confusing to the consumer/vehicle owner...

Bill

It's straightforward. The OEM has produced an ECU calibration that works efficiently and safely with the min. AKI fuel they recommend. That's really it. Turbo or not. In order to see material gains in efficiency and power running higher octane fuels one needs to datalog the car as I have shown an example of here. If you can reduce knock sensor feedback running higher octane fuel then yes you are seeing a gain. Whether this gain is worth the additional $/gal is on the user (in my example I chose to not take advantage). This is only valid for OEM calibrations...aftermarket tuning is quite different as the "bookends" for the ECU to adjust itself is more limited.

 

[silversport]

and you explain it as I understand it too...datalogs would tell the tale...unless I've misunderstood your current and past posts, if the manufacture says you are safe using a certain octane, you should be safe using a certain octane...datalogs to confirm but that is what I've followed rather than the placebo effect or anecdotal evidence of some users...

I appreciate your posts...

Bill

 

[rstcso]

The Audi preferred 91 octane or higher, though was not strictly required, so that's why I used the Shell premium (93 in our area). One of the reasons for getting the Honda Pilot was because it is naturally aspirated and is designed to use 87 octane... or higher.

Something I hadn't noticed before on the recommendation to use Top Tier gas was the guarantee the fuel "to be free of metallic additives".

Looking up MMT, I found this information on the EPA's website. A BITOG thread from 2003 indicates MMT is no longer used in the US, although not restricted from doing so.

"Methylcyclopentadienyl manganese tricarbonyl (MMT) is a gasoline octane enhancer produced by the Afton Chemical Corporation (Afton), formerly known as the Ethyl Corporation. MMT is allowed in U.S. gasoline at a level equivalent to 1/32 grams per gallon manganese (gpg Mn)."

 

[TiGeo]

and you explain it as I understand it too...datalogs would tell the tale...unless I've misunderstood your current and past posts, if the manufacture says you are safe using a certain octane, you should be safe using a certain octane...datalogs to confirm but that is what I've followed rather than the placebo effect or anecdotal evidence of some users...

I appreciate your posts...

Bill

Thanks. The other thing folks often miss is that knock sensors are v. sensitive on OEM calibrations and getting feedback is quite normal under normal driving conditions. The days of audible pinging are long gone...the ECU adjusts so fast based on a myriad of variables to what it senses as what is/may become a knock event.

 

[rstcso]

Thanks. The other thing folks often miss is that knock sensors are v. sensitive on OEM calibrations and getting feedback is quite normal under normal driving conditions. The days of audible pinging are long gone...the ECU adjusts so fast based on a myriad of variables to what it senses as a knock event.

^This is how the Audi got around requiring premium in the Q5. If lower octane fuel was used, the knock sensors would cause the engine to de-tune. This is also why mpg was higher when using premium in it.

My understanding on a car designed for 87 octane, the engine doesn't need to de-tune, so the mpg is what it is. I don't believe you'd gain much, if any, benefit (mpg) using a higher octane. What you may gain are higher concentrations of additives.

I have not tested this.

 

[TiGeo]

^This is how the Audi got around requiring premium in the Q5. If lower octane fuel was used, the knock sensors would cause the engine to de-tune. This is also why mpg was higher when using premium in it.

My understanding on a car designed for 87 octane, the engine doesn't need to de-tune, so the mpg is what it is. I don't believe you'd gain much, if any, benefit (mpg) using a higher octane. What you may gain are higher concentrations of additives.

I have not tested this.

What evidence did you have of "detuning"? As you can see in my example I posted for my Atlas that is shown as needing min. 87 and it still "pulls timing". It's more about power than measurable mpg improvements in my opinion in this discussion. A car calibrated to take advantage of higher octane fuel can run lower octane and in normal driving shouldn't see significant changes to fuel economy...with a light foot.

 

[rstcso]

What evidence did you have of "detuning"? As you can see in my example I posted for my Atlas that is shown as needing min. 87 and it still "pulls timing". It's more about power than measurable mpg improvements in my opinion in this discussion. A car calibrated to take advantage of higher octane fuel can run lower octane and in normal driving shouldn't see significant changes to fuel economy...with a light foot.

Semantics.

"Your Audi Q5 will run on regular. However, your car's computer will need to adjust to the lower grade of fuel. You are highly likely to experience a loss in fuel economy."

Last sentence below from the owner's manual: "...to achieve the rated horsepower and torque".

 

[TiGeo]

Semantics.

"Your Audi Q5 will run on regular. However, your car's computer will need to adjust to the lower grade of fuel. You are highly likely to experience a loss in fuel economy."

Last sentence below from the owner's manual: "...to achieve the rated horsepower and torque".

View attachment 285990

What I was asking is have you actually logged it to see the difference?

Where is this from?:
"Your Audi Q5 will run on regular. However, your car's computer will need to adjust to the lower grade of fuel. You are highly likely to experience a loss in fuel economy."

As I've said this is a primarily a power issue, not a meaningful mpg one as your owner's manual shows. It will achieve the EPA mpgs on 87. You will see a slight tick-up in power (read as less knock retard so a bit more timing advance way out towards redline) running 91/93 and that's only if you are pushing it/high RPMs. See my Atlas datalogs that show this perfectly.

 

[rstcso]

^This is how the Audi got around requiring premium in the Q5. If lower octane fuel was used, the knock sensors would cause the engine to de-tune. This is also why mpg was higher when using premium in it.

My understanding on a car designed for 87 octane, the engine doesn't need to de-tune, so the mpg is what it is. I don't believe you'd gain much, if any, benefit (mpg) using a higher octane. What you may gain are higher concentrations of additives.

I have not tested this.

 

[TiGeo]

Aldo I actually rented a Q5 a few years ago for some field work. Ran 87. Sent it. No issues.

 

[k1xv]

My stomach prefers filet mignon, but it will get by on hamburger.

 

[Hohn]

If your local premium is only higher octane version of the same low grade non-top-tier fuel, save your money.

But many premiums have much higher detergency levels, and that’s the main reason (not octane) I use either V Power NItro, Exxon Synergy, or BP/Amoco.

 

[nomas]

My stomach prefers filet mignon, but it will get by on hamburger.

Your stomach doesn't care one way or the other . Your BRAIN prefers Filet Mignon . Think about it ....

 

[CDNozzle]

If your local premium is only higher octane version of the same low grade non-top-tier fuel, save your money.

But many premiums have much higher detergency levels, and that’s the main reason (not octane) I use either V Power NItro, Exxon Synergy, or BP/Amoco.

Same here. I do it for the detergents and friction modifiers, not the octane.

 

[silversport]

interesting in that I thought the days of more detergents in the higher octane fuels was a thing of the past...

Bill