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E30M3 Race F10 535 R1150Rt M Coupe
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I've been doing such on my personal cars (non M) forever.

I was just up there and glad I remembered to top off just before crossing the border.
 

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I don't because my 325i has a Dinan Stage 1 upgrade which specifically calls for minimum 91 octane. It seems to be emphasized even more than the BMW requirement. BTW, the Dinan performance "increase" wasn't worth the cost...

I wonder though if anyone has first hand knowledge of someone experiencing actual engine damage by using regular gas. I can only see it happening in hot weather, flooring the throttle while going up a long hill. But I've never heard of anyone having actual engine damage.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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Back in the day I repaired many a BMW "S" engine because of detonation (ping/pre ignition) because of not enough octane.

Then Bosch started using microphones (knock sensors) attached to the engine block. They're tuned to a fairly narrow frequency and constantly listen for the onset of knock. When detected the ignition timing is reduced and fuel maps change accordingly.

As long as the regular fuel you use is a known premium brand, you're fine.
FWIW, my wife's F10 535, we run Top Tier regular on day to day. Zero issues.
 

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I have seen plenty of M54 engine damage.. burnt pistons and valves (chunks missing), gouged cylinders, warped cylinder heads, etc. but none that I would necessarily blame on regular gas...It's usually something else.

I have always used regular gas in my M54-equipped cars.
 

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2002 330 Ci
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Back in the day I repaired many a BMW "S" engine because of detonation (ping/pre ignition) because of not enough octane.

Then Bosch started using microphones (knock sensors) attached to the engine block. They're tuned to a fairly narrow frequency and constantly listen for the onset of knock. When detected the ignition timing is reduced and fuel maps change accordingly.

As long as the regular fuel you use is a known premium brand, you're fine.
FWIW, my wife's F10 535, we run Top Tier regular on day to day. Zero issues.
Yup.

I ran regular just fine in my e60 535i just fine. Same with the m54 e53 I had. I only run 93 in the vert because of the tune.

As long as it's top tier you're good.
 

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The mpg and performance figures quoted in the manual apply to higher octane fuel only. If you use lower octane and pay attention/do some tests over longer distances, you will notice the difference. I have put lower octane in on a few occasions over the years and noticed the slight difference, even if it is just a few percent. I don't believe it damages the car. I just don't believe it's best for the car even if it's slighter cheaper.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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11,875 Posts
I have seen plenty of M54 engine damage.. burnt pistons and valves (chunks missing), gouged cylinders, warped cylinder heads, etc. but none that I would necessarily blame on regular gas...It's usually something else.

I have always used regular gas in my M54-equipped cars.
One of the oft overlooked reasons for a reduction in octane (Remember "active" octane is not only what's in the tank, but what's inside the combustion chamber) is oil consumption. Introduction of oil vapor into a combustion chamber during the compression stroke will reduce the octane level at the moment.

Oil vapor mixed in with the normal fuel/air ratio will self ignite faster than fuel/air alone. Therefore because you've ignored the reasons you're consuming oil your active octane level is lower. The knock sensors will address this, up to a point.....

The additives blended into the fuel to raise octane reduce the flamefront propagation. Thus reducing possibility of detonation. Higher compression engines need such, so that the fuel only ignites when initiated by the spark plug. Detonation is most usually when the compressed fuel/air mix ignites (self compression) miliseconds before the spark plug fires off. Then the two flamefronts collide. This causes a whole host of issues.

Got an oil burner? Address it.
 

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Non-M BMWs an easily deal with regular gas unless there is a LOT of carbon deposits. I have and never even noticed the decrease in power. I generally do it in winter as I have no need for all 200+ hp in Ohio.
 

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I run the Chevron 94 octane, non-ethanol as much as possible. We run premium when in the states. The car (xi) runs much better on it with better mpg. As an offset, I cycle pretty much everywhere in the city(parking is easier).
 

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2001 325i 5mt. 2009 535xi Touring 6mt.
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I track every fillup of my cars in an app (E46 325i, E61 535xi) and cannot ever see a mpg difference with premium vs regular. Been tracking for 13 years that I’ve had my E46.
 

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Most Germans I've met run regular (95) instead of super plus (100) in their E46s. They seem to do fine but obviously suffer from worse gas mileage. Personally I always run V-Power since gas is still so cheap in the US.
 

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I track every fillup of my cars in an app (E46 325i, E61 535xi) and cannot ever see a mpg difference with premium vs regular. Been tracking for 13 years that I’ve had my E46.
You might try the non-ethanol. I find the quality of petrol in the PNW poor. The mpg improvement was bigger in our old e36 318ia.
 

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E46 F10 W204 W212
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Back in the day I repaired many a BMW "S" engine because of detonation (ping/pre ignition) because of not enough octane.

Then Bosch started using microphones (knock sensors) attached to the engine block. They're tuned to a fairly narrow frequency and constantly listen for the onset of knock. When detected the ignition timing is reduced and fuel maps change accordingly.

As long as the regular fuel you use is a known premium brand, you're fine.
FWIW, my wife's F10 535, we run Top Tier regular on day to day. Zero issues.
Good tip! My wife drives an F10 535! Great car btw.

On the E46 I've tried lower octane and I think it's fine. But on 100F+ days, heat-soaked and crawling in traffic with AC on full load and you suddenly get on the gas, I swear it suddenly backs off that timing for a split second and it's unnerving when you don't expect it. Like the fuel cuts out for a revolution or two.
 

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2001 325i 5mt. 2009 535xi Touring 6mt.
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You might try the non-ethanol. I find the quality of petrol in the PNW poor. The mpg improvement was bigger in our old e36 318ia.
I tried that for a while as until the end of 2021 the Premium fuel at all Shell stations in Canada was ethanol free. Still didn't see a difference so went back to regular. Ethanol-free should be roughly 3% more efficient I've been told but I couldn't notice it.
 

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I tried that for a while as until the end of 2021 the Premium fuel at all Shell stations in Canada was ethanol free. Still didn't see a difference so went back to regular. Ethanol-free should be roughly 3% more efficient I've been told but I couldn't notice it.
It takes a tank full or two, and or reboot the ecu. Our xi's ecu took a bit to reboot, especially after the wrath of repairs it got. I've never had good experiences with Shell. I'd also run a bottle or two of techron concentrate or BG through to clean things out.
 

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'04 325i, '02 325iT
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I track every fillup of my cars in an app (E46 325i, E61 535xi) and cannot ever see a mpg difference with premium vs regular. Been tracking for 13 years that I’ve had my E46.
Same here, I haven't been tracking as long as you have but I did experiment with switching over to 93 non-ethanol for a few tanks here and there. I noticed 1-2 mpg better on a few tanks, and worse on a few others. I normally run 87 octane that has 10% ethanol.

The difference was well within the standard deviation, which seems to depend more on driving style, weather and other conditions. I notice a 2-3 mpg seasonal change with temp and summer/winter fuel blend.

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