[hoki06]

Originally Posted by BMWCCA1

So how do you convert octane recommendations on your gas flap to the formula for octane ratings on the pump? Aren't they totally different systems of measurement/equations?

So is AKI (Anti-Knock Index) on your flap the same as the RON+MON/2 on the pump?

Yes. The US octane rating, called AKI, you see at the pump is (RON+MON)/2. If you look closely at the button you press, you should see something about "minimum octane rating (R+M)/2 method".

[Mavus]

What I noticed is that I6 n/a and turbo run smoooth with Sunoco 93. When I use Shell or Mobil there are more click clack sounds in the engine so no more those unless Sunoco is unavailable in the sticks.

[Wolf 335]

[G35POPPEDMYCHERRY]

im currently running helium.

[xlover]

Diesel gets better mileage and low end torque so typically I mix in 30-50% diesel using a funnel. Better for the wallet than using lower octane.

Adds another 4-5 mpg and 30 ft/lbs

[MachinesWithSouls]

You know what's even more fun? Throw some diesel in the tank.

[BMWCCA1]

My E28 manual says 87AKI = 91RON
My E82 manual says minimum octane for 128i is 87AKI and 89AKI for 135i. It also says no harm will come from using these minimum-octane fuel though Premium is recommended.

Wouldn't it make more sense if the pumps just said "AKI" on the buttons?

[StanDiego]

Originally Posted by br438

^^ Brings to mind the question. Our COSTCO advertises on the pump that they are selling Top Tier gasoline. Does anyone have any knowledge to the contrary?

I love saving the $$ at the pump, but I can also shop at kroger and buy gas at Shell... and be close in price with the discount. It feels like the shell stations around here have a higher chance of being shady than COSTCO. ??

Costco sells some of the best gas you can buy at any price. It's a loss leader for them, knowing many of us will shop inside after we gas up. It's the same concept of the famous hotdog and soft drink combo for $1.50. It helps to get you in the store.

[StanDiego]

Originally Posted by KMP259

FYI...Sam's Club gas is a 2nd Tier fuel without the additives used in a Top tier fuel.....that is why they sell it cheap....the internal components of a engine can only take so much detonation before it begins to fail. Your knock sensor only triggers after it has already happened.....and engines with Turbo's ...thing happen fast...for warned is for armed.

Multiple times I've searched at length but in vain to find info on Sam's Club/ Walmart gasoline. This lack of transparency discourages me from ever putting their gas into a vehicle I own.

[BMWCCA1]

Originally Posted by StanDiego

Multiple times I've searched at length but in vain to find info on Sam's Club/ Walmart gasoline. This lack of transparency discourages me from ever putting their gas into a vehicle I own.

Sam's Club says they buy their gasoline from various suppliers and can't always guarantee that every tanker has "top tier" gas. But then "top-tier" is a trade-marked appellation contrived by vehicle manufacturers for their additive packs that offer more than EPA minimums. That's so when their incomplete combustion process causes internal valve build-up, they can blame you for not using "top-tier" fuels and deny their warranty claims. I've never had any problem with Kroger or Sam's gas and that includes 245,000 miles on an M50TU engine.

I don't really see what additional additives have to do with knocking and they have nothing to do with octane ratings other than the assumption that higher-octane fuels may contain more additives than lower grades. If you don't have deposits on your valves, you're getting enough additives.

[StanDiego]

Originally Posted by BMWCCA1

Sam's Club says they buy their gasoline from various suppliers and can't always guarantee that every tanker has "top tier" gas.

I don't really see what additional additives have to do with knocking and they have nothing to do with octane ratings other than the assumption that higher-octane fuels may contain more additives than lower grades. If you don't have deposits on your valves, you're getting enough additives.

Can you provide a reference for your Sam's Club statement? I don't dispute it but that's more information than I've been able to find in multiple search attempts.

I haven't seen anyone in this thread claim "additives have anything to do with knocking" but I'll suggest they could but only indirectly. Carbon deposits in the combustion chamber can build up to an extent that they can increase the effective compression ratio (and impact fuel/air dispersion patterns) thus increasing the likelihood of engine knock, especially under load. I suspect that scenario is rare due to minimum EPA standards for fuel additives and modern engines' ability to adjust timing to compensate.

"If you don't have deposits on your valves, you're getting enough additives"

I generally agree with that statement but how is the typical vehicle owner able to determine that without taking it in for an inspection that is likely to cost more than money saved buying cheap gas? Some Ford Ecoboost motors are infamous for carbon buildup and most vehicle owners didn't discover the issue until they started having engine problems. If curious, do a Google search for "direct injection carbon buildup".

We're just trying to share knowledge and well accepted practices here. You do you. It's your vehicle and if you're happy with cheap gas, go for it. I generally buy new vehicles so I don't have to worry about what gas, oil, or service schedule was used by the previous owner of a used vehicle.

[chris719]

Originally Posted by BMWCCA1

If you don't have deposits on your valves, you're getting enough additives.

I'm not even sure there is a correlation now with direct injected engines.

[BMWCCA1]

Originally Posted by StanDiego

I haven't seen anyone in this thread claim "additives have anything to do with knocking" but I'll suggest they could but only indirectly.

Well, there was this:

Originally Posted by KMP259

FYI...Sam’s Club gas is a 2nd Tier fuel without the additives used in a Top tier fuel.....that is why they sell it cheap....the internal components of a engine can only take so much detonation before it begins to fail. Your knock sensor only triggers after it has already happened.....and engines with Turbo’s ...thing happen fast...for warned is for armed.

And I read this on the Internet, so it must be true!

Additionally, there are rumors that Sam’s Club gets their gas from Shell, Murphy Oil, Mobil, and Chevron, which is then labeled as their own brand.

Although Sam’s Club gas is not Top Tier, the company still assures the fuels’ quality with the Sam’s Club Satisfaction Guarantee.

The Satisfaction Guarantee says that Sam’s Club will replace or refund your money if you are not 100% satisfied with your purchase.

Sam’s Club is owned and operated by Walmart, which does not publicly release its gasoline source.

Some industry experts believe that Sam’s Club may use their own fuel additive and testing process to ensure they sell quality gasoline.

It’s important to note that even though Sam’s Club gas is not Top Tier, the company must still follow the guidelines put in place by certain governing bodies.

For example, the state government, Environmental Protection Agency (EPA), and the National Fire Protection Association (NFPA) have strict requirements for gas stations.

[VINCER0]

Originally Posted by hoki06

Consistent use of a Top Tier gas is the most important. Premium branded fuels (Shell, Exxon, etc.) have the added benefit of very quick clean up for both IVD and GDI injectors in as little as 1 tank with today's additive technology.

My general recommendation is to use Top Tier fuel with the appropriate octane for your vehicle. If you frequent cheap, unbranded stations to save pennies then use an aftermarket additive bottle or run 1-2 tanks of Shell/Exxon premium every ~5 tanks.

Originally Posted by hoki06

Premium fuel is at minimum higher octane and more often than not has a higher additive treat rate. This is particularly true for branded fuel stations (Shell, Exxon, BP, etc.) where the maingrade 87 octane is a Top Tier treat rate and the premium 93 octane is 1.5x or 2x the Top Tier treat rate. Unbranded fuels (7-11, Wawa, etc.) might use the same LAC treat rate in their premium fuels, my direct knowledge is focused on branded fuels.

Originally Posted by hoki06

I work for an additive company in our fuels division so I have direct knowledge of additive technology, performance, and treat rates for many fuel companies. Whenever this topic comes up I try to carefully comment to share my knowledge and teach others without giving away specifics that would be frowned upon.

Using a higher octane rating than recommended is a waste of money, yes. This is very well known. Engine controls are so sophisticated these days that they will adjust to preserve the engine despite whatever fuel you put in, to a degree. Some manufacturers now even give power ratings based on fuel octane used, see the new Ford Bronco 2.3L and 2.7L specs.

My comments are mostly around additives and their treat rates. I'm constantly amazed at how people have strong opinions with little to no actual knowledge or data. Additives are not snake oil, there is an entire industry for fuel additives and the EPA has a minimum amount required because they work to reduce deposits. Additives do make a significant difference in performance and there are millions of dollars spent by many companies to generate data to support their marketing claims.

Well said, thank you for sharing your expert knowledge with us.

[StanDiego]

Originally Posted by BMWCCA1

Well, there was this:


And I read this on the Internet, so it must be true!

LOL! Thanks, I needed a good laugh.

[F32Fleet]

Knock sensors will retard timing and engine will make a few less HP. How much less is anyone's guess.

[Bugs Meany]

Originally Posted by dizz81

Wait is this in non M BMW's? I'm just curious but my M definitely says min 91.

From the manual:

Recommended gas quality
BMW recommends AKI 91.
M Performance model: BMW recommends AKI 93.
Minimum fuel grade
BMW recommends AKI 87.

Can you “recommend” a minimum? Rollercoasters don’t recommend that children meet a certain height; they insist on it.

[purplerocket]

Always premium especially when you have a remaped car. on my car when i use regular one i fill like its dying, cant accelarate fast and consumes more so 99% i use premium gas. Also its cleaner means less trouble with injectors and low and high fuel pressure

[shawnhayes]

It's already been said here, but Premium fuel from premium distributors tends to have the cleaner formulations with the higher additive packages. If all other things were EQUAL, one could use lower octane when you're just toodling around town, but then you're always wondering if you tromp on the throttle do you have enough octane to prevent knock.

Easier just to have it right, all the time.

Shawn

[Anderson11]

As a matter of course I add a can of Berryman Chemtool fuel system cleaner every 1000 miles. Have had great success over the years with this product for M2C and e90.....

[shawnhayes]

Originally Posted by Anderson11

As a matter of course I add a can of Berryman Chemtool fuel system cleaner every 1000 miles. Have had great success over the years with this product for M2C and e90.....

And how much does that cost? Is it cheaper than just using high quality grade fuel?

And then, WHY?

I'm not saying fuel system cleaner is a bad idea, I'm just saying that skimping on fuel that you then NEED a fuel system/injector cleaner is a bad idea. False economy.

Shawn

[bimmer456]

Originally Posted by bucketfoot

Other than performance and possibly gas mileage suffering, nothing is likely to happen. The electronics in modern engines will adjust for the quality of fuel being used. However, I do not know if they could try to use this against you for warranty purposes.

That said, why would you bother getting a BMW if you aren't going to use the proper fuel

It says on the fuel door to not use anything below 89 minimum.