[jeffc83]

I would like to discuss this with the folks here as I call BS on a company that tests just 6 cars then releases a full 68 page report on Premium Fuel. Am I wrong here?

http://www.thetruthaboutcars.com/201...th-cash-cases/

[Livetodrive]

I see nothing wrong with the article. They tested a few cars with fuel specs that allow regular fuel, but recommend premium. It doesn't apply to newer Bimmers, which require premium. The use of a lower than specified octane can cause knocking and damage the engine.

[BimmerMat135]

Originally Posted by jeffc83

I would like to discuss this with the folks here as I call BS on a company that tests just 6 cars then releases a full 68 page report on Premium Fuel. Am I wrong here?

http://www.thetruthaboutcars.com/201...th-cash-cases/

Look like a bunch of amateur. Only the Miata and the Jeep require premium gas to start with. The Miata only has a 10.8:1 compression ratio so no problems with regular fuel there. The Jeep is only pushing 160hp VW does have a 1.4 turbo pushing 150hp on regular again there probably the regular could do the job. In the end use the fuel recommended for your car and everything should be fine. I would like to see the result on something heavily boosted like a CLA45 not sure the regular would do good there.

[jeffc83]

Originally Posted by Livetodrive

I see nothing wrong with the article. They tested a few cars with fuel specs that allow regular fuel, but recommend premium. It doesn't apply to newer Bimmers, which require premium. The use of a lower than specified octane can cause knocking and damage the engine.

I suppose they covered their asses by saying most cases. I'm not an Audi expert but don't they require Premium as well?

[Billfitz]

I tested mine with two tanks of 89, then two tanks of 91, then two tanks of 89 again. No difference in acceleration or fuel economy, so I stuck with 89. I've done the same with every car I've had going back 30 years, with the same results. Some driving styles might benefit from higher octane, mine doesn't.

[jeffc83]

Originally Posted by Billfitz

I tested mine with two tanks of 89, then two tanks of 91, then two tanks of 89 again. No difference in acceleration or fuel economy, so I stuck with 89. I've done the same with every car I've had going back 30 years, with the same results. Some driving styles might benefit from higher octane, mine doesn't.

Thank you for your input; the gas station I go to offers 87, 89 and 93 so I always put in 93. I had a feeling this would be the case...

So now the true question is: has anyone tried running 87 and can the vehicle run reliably and well for years to come using it? (forget performance) Required might not be so "required" after all...

[Seba77W]

In Chicagoland we usually get 3 choices
87
89
93

So I stick with 93.

[jparnes1]

So what are we bickering about here? Saving 30 cents a gallon? Let's say $3 per fill up, $12 per month, $144 per year. Are you kidding me?
We're driving $50k+ cars for god's sake! Just put in what the manufacturer says the engine needs and find some other place to save $144.

[jeffc83]

Originally Posted by Seba77W

In Chicagoland we usually get 3 choices
87
89
93

So I stick with 93.

I see 94 at times but usually put 93 in.

Not that I want to truly use 87 but it's interesting to see if it's all a big lie in terms of a requirement

[Seba77W]

Originally Posted by jparnes1

So what are we bickering about here? Saving 30 cents a gallon? Let's say $3 per fill up, $12 per month, $144 per year. Are you kidding me?
We're driving $50k+ cars for god's sake! Just put in what the manufacturer says the engine needs and find some other place to save $144.

I completely agree with you. However I'm not sure where you are located but in Chicago it's not uncommon to pull up to a gas station and have almost $1 difference in 87-89-93 still not a big difference but to some people might equal to about $5-$10 more every tank full.

[jeffc83]

Originally Posted by jparnes1

So what are we bickering about here? Saving 30 cents a gallon? Let's say $3 per fill up, $12 per month, $144 per year. Are you kidding me?
We're driving $50k+ cars for god's sake! Just put in what the manufacturer says the engine needs and find some other place to save $144.

See, that's the problem! I went to a car website to read up on cars, not AAA's report on premium gas usage based on just 6.

The debate is if a BMW "truly" "requires" premium or not. (AAA did cover their ass by saying "in most cases" so I am no longer attacking the article itself) I would personally like to know if it's all a load of crap yet the outcome will make no difference as I always load her up with 91 or 93. I know I know, you don't have to say it but inquiring minds do want to know

[jeffc83]

Dammit I'd better change the topic title as this is going way off track

[dogmush]

I can't speak to my BMW, because I put 93 octane in it, and don't feel like experimenting.

But my previous car was a modded 2003 Ford Cobra. That's a blown 4.6 liter V8. 8.5:1 compression ratio, and I was running 16.5 lbs of boost. I data logged the difference between the 93 octane my tune was for and 87 octane. The car pulled timing under load pretty much as soon as it hit full boost. Any time the engine was under 50% or so load there was no difference but under load and boost the computer sensed knock and pulled timing early. I was playing with the tune at the time so we were doing dyno runs and data logging. The total difference in HP wasn't that much, but the engine definitely didn't like detonating. I damaged some exhaust valves in the course of one afternoon of tuning.

I'd suspect strongly that data logging would show the same on turbo BMW engines. There are engines that are designed to run while detonating, but my N55 doesn't sound or feel like one of them. The particular fire you would be playing with is how fast the knock sensor senses the detonation and how quickly the engine can pull timing to counter it. It doesn't take very much detonation at all to damage things. As a driver you might not even notice the knocks before the engine pulls timing, but your rings and valves will notice them.

As to driving, I'd suspect you will never feel the difference from pulling 15-ish* of total timing power and acceleration wise. But you're still putting a lot of stress on the engine for those 2 or 3 revolutions between full boost, and timing getting pulled.

[Billfitz]

Originally Posted by jeffc83

The debate is if a BMW "truly" "requires" premium or not.

If you consistently drive hard, probably. If you don't, probably not. IMO the main reason why not only BMW but most brands recommend premium is that the uninformed might feel that their car isn't all that it should be if it doesn't claim to need premium.
As for 87, I have it on good authority, people in the gasoline industry, that more often than not what comes out of pumps labeled 87 is actually 89. The more grades that a tanker has to haul the less of each it can haul, and that impacts greatly on the cost of getting it to the pumps. There's no requirement that a pump listed with 87 actually deliver 87, it just has to deliver at least 87. If the distributor figures out that it's less expensive to put 89 in the 87 tanks than to deliver both 87 and 89 that's what he'll do. By the same token the 89 tank might get filled with some 91 or higher, especially if the truck has left over 91 that he'd rather dump into the 89 tank than haul it back to the barn.

[jgoens]

Here is a guy who decided to experiment.

http://f30.bimmerpost.com/forums/sho....php?t=1448080

[KosmoK]

Why would BMW recommend 91 if it's not needed? If anything, the requirement for 91 would hurt sales. I don't by the argument that "It must not be a performance car because the manufacture does not require premium fuel." When the lease was up on my '06 325, I turned the car in and leased a Cadillac. One factor in my decision was the GM did not require premium fuel in the Cadillac. (Premium fuel is about $1./gal more expensive than regular fuel in my neck of the woods. Part if the reason for the higher cost of premium fuel here is non-oxengated.)

[jeffc83]

Originally Posted by jgoens

Here is a guy who decided to experiment.

http://f30.bimmerpost.com/forums/sho....php?t=1448080

Interesting even if it was a 335! That's quite the problem!

[jeffc83]

Originally Posted by Billfitz

If you consistently drive hard, probably. If you don't, probably not. IMO the main reason why not only BMW but most brands recommend premium is that the uninformed might feel that their car isn't all that it should be if it doesn't claim to need premium.
As for 87, I have it on good authority, people in the gasoline industry, that more often than not what comes out of pumps labeled 87 is actually 89. The more grades that a tanker has to haul the less of each it can haul, and that impacts greatly on the cost of getting it to the pumps. There's no requirement that a pump listed with 87 actually deliver 87, it just has to deliver at least 87. If the distributor figures out that it's less expensive to put 89 in the 87 tanks than to deliver both 87 and 89 that's what he'll do. By the same token the 89 tank might get filled with some 91 or higher, especially if the truck has left over 91 that he'd rather dump into the 89 tank than haul it back to the barn.

I've heard this before as well and along side that, I never fill up when the truck is delivering gas for obvious reasons

[jeffc83]

Originally Posted by dogmush

I can't speak to my BMW, because I put 93 octane in it, and don't feel like experimenting.

But my previous car was a modded 2003 Ford Cobra. That's a blown 4.6 liter V8. 8.5:1 compression ratio, and I was running 16.5 lbs of boost. I data logged the difference between the 93 octane my tune was for and 87 octane. The car pulled timing under load pretty much as soon as it hit full boost. Any time the engine was under 50% or so load there was no difference but under load and boost the computer sensed knock and pulled timing early. I was playing with the tune at the time so we were doing dyno runs and data logging. The total difference in HP wasn't that much, but the engine definitely didn't like detonating. I damaged some exhaust valves in the course of one afternoon of tuning.

I'd suspect strongly that data logging would show the same on turbo BMW engines. There are engines that are designed to run while detonating, but my N55 doesn't sound or feel like one of them. The particular fire you would be playing with is how fast the knock sensor senses the detonation and how quickly the engine can pull timing to counter it. It doesn't take very much pre-ignition at all to damage things. As a driver you might not even notice the knocks before the engine pulls timing, but your rings and valves will notice them.

As to driving, I'd suspect you will never feel the difference from pulling 15-ish* of total timing power and acceleration wise. But you're still putting a lot of stress on the engine for those 2 or 3 revolutions between full boost, and timing getting pulled.

Thanks for that detailed explanation; solid info there and somehow, that made perfect sense to me from beginning to end. 91 or 93 is definitely required with my understanding but 89 mixed with 91 shouldn't harm anything. (keyword shouldn't) In other words, the requirement is indeed a requirement and not some BS recommendation. Thanks again for your input.

We've also confirmed that the car runs just fine on 90

[CalCarNut]

Pulls timing which knocks down power. The small savings isn't worth it to me on a car I'm buying. On leases, people seem to not care as much as it'll be 'the other guy's problem'. Cheap and selfish but whatever. I run max octane all day/every day. In a car with a potential $20K engine replacement bill, I'll pay a little ins money monthly.

[Billfitz]

Originally Posted by KosmoK

Why would BMW recommend 91 if it's not needed?

Look at the various comments in this thread, and numerous others, by the true believers in high octane and the answer should be clear.

[BEAR-AvHistory]

Two examples of my timing getting pulled when available octane level did not support the boost during testing.