[StepMassive]

I'm curious if anyone knows the impact of filling my M240i with 87 octane gas instead of the the recommended 91 octane?

I know some BMW models "require" 91 octane, but the M240i only "recommends it". The owner's manual lists a "minimum" of 87 octane.

Am I risking any long-term health of the engine with 87 octane, or just loosing out on a bit of performance...or what?

[FastTyger]

It won’t damage the engine, but you will down on power. BMW engineers know what’s up, so believe the manual.

[MPR]

If you bought the car I'd put nothing less than 91 in the tank. If leased, you're only potentially screwing over the future owner.

[LivingInSalt]

I’d never put less than 93 in mine

[jpcoop]

Originally Posted by LivingInSalt

I’d never put less than 93 in mine

You can't easily get 93 on much of the west coast

Also, my manual says minimum 89... I always use 91 though.

[danallxt]

Originally Posted by jpcoop

You can't easily get 93 on much of the west coast

Also, my manual says minimum 89... I always use 91 though.

Same here, manual (and fuel filer sticker) for my 2022 M240x is 89 min, not 87. Did they lower it for 2023's? re: first post of this thread?

[MrPickles]

This is similar to someone buying a Ferrari and washing it with dish soap. Why buy a premium car and feed it garbage?

[idontsave]

Originally Posted by StepMassive

Am I risking any long-term health of the engine with 87 octane, or just loosing out on a bit of performance...or what?

Yes to both. Fill with highest octane available if long-term engine health and optimal performance matter to you.

[danallxt]

This is similar to someone buying a Ferrari and washing it with dish soap

For really dirty cars ya can't beat Dawn dish soap and the 3M green scrubbing pads.....( i get paid for product name placements).

[danallxt]

Originally Posted by Rw-M240

93 Octane for east coast is the same at 91 for Midwest

huh? nope, wrong!
Or i guess one could say the gasoline is the same EXCEPT for the octane rating.

[M240SLC]

Originally Posted by danallxt

huh? nope, wrong!
Or i guess one could say the gasoline is the same EXCEPT for the octane rating.

I think he confused "Midwest" with "Rockies." Here, they sell 85 octane, trying to say it's no different than 87 at sea level. Same goes for 91. I also know of only 1 station that sells E85 in the SLC to Provo area.

[RockCrusher]

Originally Posted by StepMassive

I'm curious if anyone knows the impact of filling my M240i with 87 octane gas instead of the the recommended 91 octane?

I know some BMW models "require" 91 octane, but the M240i only "recommends it". The owner's manual lists a "minimum" of 87 octane.

Am I risking any long-term health of the engine with 87 octane, or just loosing out on a bit of performance...or what?

There could be a bit of risk to engine health using 87 but if the owners manual says it is ok then it is ok. (But I'm thinking no way would I use 87 in a 240i (or even my 230i).

If the engine is tuned to make good use of a higher octane of gasoline, and this includes the engine controller will allow timing to advance, using the highest recommended octane is best.

My Porsche cars were spec'd to 93. 'course, in CA 91 was all that was available. But on a road trip through Wyoming I got a chance to fill up my Porsche 996 Turbo with 93. What a difference. Amazing.

And it highlights that turbo charged or supercharged gasoline engine octane requirements don't go *down* at higher elevations. I observed boost level. The boost hit -- and not hit as in a glitch but stayed at for a time -- 0.8 bar and then 0.9 bar. At near sea level the boost level would -- under the right conditions -- only get to 0.7 bar.

Techs told me this is normal. The engine controller seeks to provide the torque the driver requests via the throttle. If it can do this with just 0.7 bar of boost that's all it will allow. But it can allow more provided there is nothing going on -- misfires/knocking -- that would cause the boost to be limited.

While all my cars have required 91 with the exception of the Porsche cars which didn't require 91 but were designed to run best on 93 but for which Porsche ok'd the use of 91 I have run 91 all the time. I have even avoided using less than 91 when driving in the mountains.

With lower octane to avoid knock/detonation timing is retarded. This is a horrible way to address this but it is better than allowing detonation.

Reducing timing results in higher exhaust gas temperature. And lower engine efficiency. The fuel/air mixture is lit off later in the power stroke. This reduces pressure in the cylinder which eliminates detonation but the combustion flame front and pressure lags the piston a bit as it goes down the cylinder. A result is not as much of the chemical energy produced by the burning air/fuel mixture is used to generate mechanical energy. The unused chemical energy just makes for hotter exhaust.

With the right octane the engine has better off idle pick up and throttle response. And with my Turbo mid range and WOT were not too shabby either...

Really made for a more enjoyable driving experience.

Yeah, 93 costs more than 91 if 93 is even available. And while fuel economy might improve with 93 in the gas tank probably not enough to make up for the price premium 93 has compared to 91.

Except for my coming upon 93 in Wyoming -- and while I didn't confirm this I suspected it was rather common there -- I have never found 93 where I lived in CA nor on my usual route out of CA for points east which consists of me driving from the SF bay area down to Bakersfield then east on 58 to Barstow and then taking I40 on east.

Now I live in Benton County AR and while I can find 91 ethanol free here so far no 93 with or without ethanol.

Might add since arriving here I have tried 91 ethanol free and then 91 E10 in a number of vehicles: 2018 Dodge Hellcat, 2020 M-B Metris van, 2020 Dodge Scat Pack, 2023 BMW 230i and more recently a 2023 MINI Cooper S. Except for the Scat Pack all other engines were supercharged (Hellcat) or turbo charged. I can't tell the difference. Engines run the same, feel the same, and as best I can tell gas mileage remains unchanged regardless if 91 ethanol free or 91 E10 is in the tank.

[emcee1011]

C'mon, spending 60k on a luxury sports car and putting anything less than 91 in it is a sin.

[danallxt]

Originally Posted by emcee1011

C'mon, spending 60k on a luxury sports car and putting anything less than 91 in it is a sin.

almost as bad as not ever driving it in sports plus.

[emcee1011]

Originally Posted by danallxt

almost as bad as not ever driving it in sports plus.

I personally will never touch the eco button

[TargaM2]

Why would you even consider putting anything but the best available fuel in ?
I am constantly amazed by people that make excuses & state there is no benefit & put shit fuel in a car because they are simply too tight fisted.
It’s the cheapest & easiest thing you can do for ANY car. No need for any discussion it’s as simple as that.

[apez]

Is there any drawback or benefits to using 93 instead of 91 on a stock car?

[RockCrusher]

Originally Posted by apez

Is there any drawback or benefits to using 93 instead of 91 on a stock car?

A possible benefit is the engine may run better with 93. But my limited experience is this is if the manufacturer (Porsche in this case) spec'd the engine for 93.

But of course for those of us not in Germany or some other areas where 93 (AKI) which in Germany is 98 (RON) is not available 91 was ok to use.

However, if you have access to 93 you can try it. If the engine runs better there you are.

If it does run better there is the cost and availability. Since I don't have 93 where I live (northwest Arkansas, USA) availability is my problem in that I can't even use 93 to see if it makes a difference.

If available the cost might be prohibitive. Now on another forum regarding gas prices i have seen pics of the fuel pump and prices for all octane grades: 87, 89, 91, and 93 (and E85 in some cases). From what I recall -- and to my surprise -- 93 was not that much more than 91. But that is no guarantee that would be the case everywhere.

The time I was able to fill up my 996 Porsche with 93 (in Wyoming) I don't remember what I paid for 93 but I think I would have remembered if the price was much above 91. I would have still tried it though.

If 93 was handy and price competitive I might be inclined to use it in my 230i. I run 91 ethanol free in my cars mainly because the station most convenient to me sells 91 ethanol free. The times I have done a price comparison between 91 ethanol free and 91 E10 the ethanol free blend was a nickle or so per gallon more expensive. This is not a deal killer.

However, I admit that the vehicles I have fueled with 91 ethanol free not one engine reacted favorably to it. Without the credit slip in my hand I can't tell from how the engine runs which flavor of 91 is in the tank.

So it is mainly from habit and convenience I continue to use 91 ethanol free.

[dasistato]

93 only. Why buy a sports car if you are going to put honda gas?

[danallxt]

Originally Posted by dasistato

93 only. Why buy a sports car if you are going to put honda gas?

Didn't know Honda produced gasoline, can't find any Honda branded gas stations around here? They seem to produce some pretty darn good race engines so I'd like some of their quality gas.

[tahoeacr]

Originally Posted by danallxt

Didn't know Honda produced gasoline, can't find any Honda branded gas stations around here? They seem to produce some pretty darn good race engines so I'd like some of their quality gas.

Especially the fuel that Red Bull F1 uses in their Honda engines. I got some barrels of F1 fuel from Indy once. Put it in my Evo and tuned it for that fuel. Got 65 WHP from it. Got two of the barrels still left.
As far as my M240, it's 91 non ethanol. That's the best I can get around here. Probably not a 93 pump within 2,000 miles of here.

[M240SLC]

Originally Posted by tahoeacr

Especially the fuel that Red Bull F1 uses in their Honda engines. I got some barrels of F1 fuel from Indy once. Put it in my Evo and tuned it for that fuel. Got 65 WHP from it. Got two of the barrels still left.
As far as my M240, it's 91 non ethanol. That's the best I can get around here. Probably not a 93 pump within 2,000 miles of here.

Same here. If I get a JB4 after break-in, I might be inclined to mix in some E85 to bump the octane number up a bit. Can't really compare E85 around here though, only 1 station in Utah sells it.