On the day you became a BMW owner, you knowingly committed to owning a premium car and the maintenance costs that come with it. But there’s a difference between being a responsible owner and mindlessly spending money on unnecessary items just because they’re assumed to be “premium.”
A great example of this is fuel. While it’s commonly assumed that the performance heritage of your Bimmer’s engine grants it the right to sip only the finest gas, the truth is that in most BMW cars, you can get away with running regular and save a few pennies doing it.
So how can you tell if your car qualifies, and what are the tradeoffs involved? Read on and learn, Bimmer brother!
We Don’t Need No Stinkin’ Octane!
To understand the pros and cons of premium fuel, you must first understand what makes it premium. Most regular fuel has an 87 or 88 octane rating. Premium fuel has a higher octane rating — 93 in most states or 91 in California, where God hates gearheads.
This rating is derived from the stability of the fuel. A lower-octane fuel will combust under less pressure than a higher-octane fuel. This makes high-octane fuel better for engines that create higher cylinder pressures during the combustion cycle. We call these “high-compression engines” for obvious reasons, and while some BMW engines do use very high compression, not all of them do.
The Risks of Low Octane
What’s the big deal with fuel combusting under lower pressure, then? In a word: detonation. Detonation is the term used to describe a situation where the mixture in your cylinder combusts before a spark is introduced. The result is that engine components that want to rotate in a very specific fashion, and that are already subjected to very extreme forces, are subjected to forces in the opposite direction.
This is bad. When it happens, we call it a “ping,” or — if the forces are strong enough to force the connecting rod backwards into other components — a “knock.” Knocking is extremely hard on your engine, but luckily, humans have been building engines for long enough that we’ve engineered some clever ways to avoid it.
Why Most BMWs Can Run Low-Octane Fuel
The way engineers help you avoid pings and knocks is by using an octane sensor. This sensor detects the type of fuel you’re running and retards the spark timing in your engine so there’s little to no risk of detonation if fuel might be less stable than recommended.
The presence of this sensor in most cars built later than 1996 means that, if your car was built later than that year, you can run regular fuel without much fear of damage to your engine. The only possible exception would be that under heavy load, for example, and while pulling up a steep hill, you might still experience detonation, but mild detonation is not as detrimental as a full-blown knock.
This is not to say that you get all the benefits of premium fuel while running a lower octane. Retarding spark timing means your engine won’t run its best, and you’ll probably experience a slight dip in power.
Which BMWs Suffer Most From the Cheap Stuff?
While any engine might make less power burning low-octane fuel, the effect is magnified in boosted cars and the high-compression engines we mentioned earlier. So how can you tell if you own a car with a high-compression engine?
Generally, BMW M cars fall into one of these two categories. The fabled e39 and e46 cars from the early 2000s each featured 11.5 to 1 compression, which is some of the highest found in a street car. BMW recommends only using premium in these cars, as with all their cars, but it’s models like these where you’ll feel the effects most. Sorry, M owners, but that extra gusto comes at a price.
Choose at Your Own (Small) Risk
The fact remains: technology has mostly mitigated the threat of major damage from running low-grade fuel. Ultimately, you have to decide what level of risk you’re comfortable with.
Standard BMWs are at a minimal risk of damage and even very high-performance cars probably have the technological wizardry to adjust at the cost of horsepower. How acceptable a potential ping is in your Bimmer is something each owner must decide. And so your engine’s fate lies in your gas pump-wielding hand. Choose wisely!
First off, great article, thanks for writing up. Question for you – is there a way I can tell, depending on my car, which level of octane is optimal and which level is acceptable? I know with my current 528i, I can probably get by easy with regular based on this read. However, I’m looking to lease a 530e and curious if maybe because the engine is paired with an electric engine, the new car may require higher octane than my outgoing one. Is it listed anywhere in the car or manual for example?
It does in the fuel door. 91 recommended. Minimum octane 89.
Just an FYI, my Mom has had 2 BMW 528i (2012 & 2015) and if you don’t put at least Mid-Grade in the car it will end up stuttering when you accelerate. The minute she switched from Regular to Mid Grade it stopped. If you want the best performance for your Turbocharged vewhicle, pay the extra $5.00 total and get Premium gas, you won’t be dissapointed.
Thank you! I believe like what was said below, it’s in the fuel door and also the manual, which is probably online too. I would also check with other 530e owners and see their thoughts. By some of the comments below, it can be pretty different for each person.
My reasons for running Premium fuel have to do more with Ethanol than octane. Although highly anecdotal, my experience in using even 91 octane for a year was that I began consuming oil for the first time ever. Also had a hard time starting in cold winter mornings. After some research, I found that Ethanol causes damage to seals, plastic, and cold starting issues. Even BMW officially advises that although 10-15% ethanol may be OK, the car may experience hard starting.
So I use fuel that has no ethanol which happens to be 94 Octane.
Also in regards to high compression, my 525i has the N52 engine which is not highly powerful but still features 11:1 compression ratio.
Whoa..where are you getting this no ethanol gas?
Lol Chevron 94 has no ethanol in Canada. Does that have ethanol in the states?
http://www.pure-gas.org/extensions/map.html
I had never heard of an octane sensor, so I tried to look it up. I see no reference to it outside of this article. Do you have a source for this?
As far as I know, BMW uses traditional knock sensors that react to pinging, not an octane sensor that proactively sets the timing.
Same. I never heard of this ‘active sensor’. This article should be put down immediately for incorrect fantasy fiction. A lot more ignorant people will end up pouring regular gas into their cars. Report this article to bmw also.
I have an E46 M3 and I only use Premium gas 91. I’ve never thought about using 94 since the manual calls for 91 octane. I figured why waste money on 94, it’s probably overkill. 94 is most likely for old 60’s and 70’s muscle cars.
I’m on my third month with my 2007 320i. Ran regular a month or so till I saw others recommended premium. Here on Japan it runs F1 from Shell that’s rated 100 octane. Cost 1.20$ a liter. Average for Japan. Runs way better. You can feel the difference in acceleration and response. Also about and extra 60 kilometers range per tank. I like the changes. Engine seems happier too.
careful with the extra range stuff, most of the time it comes from an anti-foam additive so you can put more liters in your tank …
From what I understand “premium” gas it slightly less prone to detoriation. As it can take months before I refill my i3 rex with gas I always go for “premium”.
Months before you refill… must be nice haha!
Huhu, funny to see americans debate between EU95/US91 and EU98/US93 while we have the choice between EU95, 98 and 100 or 102 … unfortunately we have to go away from the EU95 as they most of the time include 10% of Ethanol (called SP95-E10)
I don’t even know how to translate US88 in EU …
I’ve seen a fifth gear episode where they tested EU95 against 98 on a power bench. Basically, a powerful atmospheric engine (subaru boxer in this case) had a small power bump while the city car (a Clio if I’m not mistaken) showed no difference at all.
BMW tells me to put 98 in my E85, so be it …
Ignorance is bliss, telling people advice from your ignorance is dangerous. So are you an engineer? Design lots of motors? Relying on sensors to hopefully stop pre-detination is very bad. You may not hear the early explosions but they are there and they will wreck an engine quickly. It is not only compression that effects the fuel grade it is also the total timing, your ignorance shines here, BMW uses a lot of total timing in there motors to get every last drop of horsepower. The computer only has so much leeway in how much it can retard a motor. Did you hook up a monitor to see the difference in total timing? Use the factory rated fuel since they spent millions developing an engine and know a lot more than a blogger.
Are you an engineer? Good question. If you are you would know your precious BMW happens to have an engine… not s motor. Something Charles Kettering GM’s head of engineering for decades was annoyed with. He would not allow the term motor used in his research labs. Also your advice that pinging happens although you can’t hear it is patently false. The knock sensor incrementally retards spark timing until no pinging occurs. It does not exist.
Premium gas actually burns )explodes) a tiny bit slower thus allowing spark timing to be advanced. 6,000 RPM = 100 revolutions per second. That is 50 explosions per second.
Things are happening very quickly under the hood. Indide that …engine… of yours. Anything over 9.5 compression ratio will benefit a hit from higher octane.
I think you need some help with your spelling before you start asking about who is and who isn’t an engineer.
I’ve been wondering what the effect on future engines and gasoline costs would be if we dropped regular and just had Plus and Premium. The cost of Premium and Plus would go down some but be higher than regular. This would allow manufacturers to create more efficient engines with higher compression.
Original research here: I’ve owned all variations of the M52 and the M62TU engine. They all ran regular just fine. My E90 M3 on the other hand hated it. The selling dealer filled the tank with 87 and it pinged like crazy until I refueled with 93 on the way home.
I’m going to retire to Arizona & buy a solar carport for my i3.
NOBODY LISTEN TO THIS ARTICLE. 89 is OK. lower octanes shouldnt be used even though the vehicles can adjust for a lower grade fuel. also, do a google search for “top tier” gas stations and do yourselves a favor.. try to fill up at these stations only.
Shell V-Power premium since day 1.
THIS FANTASY FICTION SHOULD BE TAKEN OFF FROM HERE IMMEDIATELY. A LOT MORE IGNORANT PEOPLE WILL END UP POURING REGULAR GAS INTO THEIR CARS AFTER READING THIS FICTION. REPORT THIS ARTICLE TO BMW ALSO.
Why is it fiction?
This is pure fiction:
“The way engineers help you avoid pings and knocks is by using an octane sensor. This sensor detects the type of fuel you’re running and retards the spark timing in your engine so there’s little to no risk of detonation if fuel might be less stable than recommended.”
There is no octane sensor. There are knock sensors, but they are not intended to correct for intentionally putting in the incorrect fuel. They are safeguards against engine damage from poor quality gasoline. Retarding ignition timing results in incomplete combustion, increased emissions, and reduced oxygen sensor and catalytic converter life.
This article is incorrect and irresponsible.
Then I guess those guys are wrong also https://www.edmunds.com/fuel-economy/to-save-money-on-gas-stop-buying-premium.html
and those guys
http://www.nytimes.com/2008/08/03/automobiles/03OCTANE.html
BMW, for example, recommends that all the cars it sells in the United States use premium fuel, but they will run on regular.
“There generally isn’t any harm done to the engine by using lower-octane fuel,” said a BMW spokesman, Thomas Plucinsky. “Because our engines do have very good forms of knock sensing and are able to deal with lower-octane fuels, you will not have any drivability issues. You will, however, lose some of the performance.”
and this http://www.theglobeandmail.com/globe-drive/culture/commuting/do-i-really-need-to-use-premium-fuel-in-my-premium-suv/article4102182/
You’re correct that I confused the knock sensors. But, as Horatiu also points out, it doesn’t change the fact that BMW themselves says there isn’t any harm done by using lower-octane. So to each his own, but it’s not “irresponsible.”
wisdom? put whatever the manual says in your car.. simples
If you’re not using 93 octane in your BMW then don’t love your BMW as much as you think you do. Premium gas bring better performance. Who cares about saving a couple bucks? BMWs are made to perform.
No one denies that and all articles point to what you’ve said. But someone called us on being wrong about this and we just cited some other publications saying the same thing.
In our defense, the article ends with…a disclaimer so we, in no way, suggest you should be using anything but premium. All the article does is talk about the differences and pros/cons.
My i8 calls for 91 as a minimum octane recommended is 94. You can feel the difference on startup. The engine runs so much smoother. For the i8 power is more consistent with temperature, under load and on grades with 94. I don’t notice a big difference switching from 94 to 100 except the price. Most likely due to the fact the car is not tuned to take advantage of gas over 94. I do like the fact the higher octane has no ethanol. I get about 600 miles to 10 gallons…. I don’t see a big change in mileage between 91 and 94 the hybrid aspect make this hard to judge.
You already paid a premium for the car. Why wouldn’t you just the bite the bullet & pay what the engineers designed the car to run best on?
It works out to a couple bucks per tank & frankly, it’s just one less thing to go wrong.
You have a warranty on a vehicle that cost you a minimum of $30k just for an entry level model. If you can afford that–just buy the fuel it was designed to run on & save yourself a possible cat fight with BMW over a potential warranty issue if something does go wrong—or just go buy a Honda & run it on regular.
I had to run a couple gallons of regular to top off my tank because we could not get premium in Houston after Hurricane Harvey & I had to drive to N. Texas.
When I asked the BMW tech in League City TX he said top it off, run it all out & then fill up with premium at the first opportunity.
So I did.
If you think you can afford a BMW—then afford the gas for it.
Relax dude. Regular can not possibly “hurt” your dearly beloved engine. Will it have less acceleration power? Yes. Slightly. Will it hurt the engine? Not possible.
At constant RPMs or with relatively undemanding driving over short times….no.
But the car will not perform to the standard it was designed for and if you run it in high demand scenarios like say towing, especially in hilly or higher speed applications— it most definitively isn’t good for your engine. Especially true if you drive it like that often.
You will get constant pinging, knocking and poor performance. There is no way that will not affect your engine over time.
My post really just speaks to common sense—you paid a premium for a high end automobile. Take care of it. If the extra .40 or .50 a gallon is that big a drag on your budget then don’t buy one. You can’t afford it.
My car ran for 2 years on regular then I had to spend $600 plus because of the slow damage it did.
“It wouldn’t impact fuel economy. And it wouldn’t impact the emissions. … BMW, for example, recommends that all the cars it sells in the United States use premium fuel, but they will run on regular. “There generally isn’t any harm done to the engine by using lower-octane fuel,” said a BMW spokesman, Thomas Plucinsky.Aug 3, 2008
I run regular in my BMW engine and the bottom line is that I do not notice the lost power at the top end or the 2-3% efficiency loss but I do most definitely notice the extra cash in my wallet. And I am speaking from Canada where premium is 15% more money which is over $10 a tank every single time I fill up.