Premium vs Plus gas - Page 2 - Mercedes-Benz Forum

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post #11 of 17 (permalink) Old 05-12-2008, 09:11 PM
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On the one hand, we have our BW experts.
On the other, here is a relevant article from PopMech.

13 Must-Know Tricks to Max Out Your Road-Trip MPGs - Popular Mechanics
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post #12 of 17 (permalink) Old 05-13-2008, 06:14 AM
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Please read the other 7000 postings on this same topic.
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post #13 of 17 (permalink) Old 05-13-2008, 08:18 AM
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Originally Posted by mlfun View Post
Mike, Jay, Cmitch,

Melissa asked "Would there be any problems ... ?".
None of your replies addresses that question.
I think you know this has been beaten tirelessly to death in many other forums and many other threads including this forum. A search would show how many times it's been discussed and the reasons for not burning cheap gas. If you'll remember, 43sqd posted a pretty good piece of factual information concerning how MB engines work and why it could potentially be harmful to burn 87 octane in it. He specifically said that the knock sensors in the engines didn't work until operating temperatures reached 160º. So, a cold engine would allow potential damage to take place, over time. Plus, no one seems to get it that 87 octane burns dirtier than the 91 or 93. This results in carbon deposits on piston heads, valves and raw, unburned fuel to enter the catalytic converter, as I've mentioned in the W163 thread that everyone wants to argue with.

MB engineers know that the vast majority of drivers are going to throw the crap in their tank, no matter what they recommend, so, they designed these engines to take a little abuse. They tuned computers to adjust fuel-air mixture when a 'knock sensor' indicates there's pinging going on. Knock sensors do not change the nature of the fuel, though. It will still burn dirtier than 91 or 93. So, how much is too much? Do you know? Probably not anymore than I would know because no two engines can be built exactly alike. You'll have one guy say, "Hey, I'm not having any problems. My gas mileage is great". Meanwhile, what he didn't tell you is that his car just went in the shop last month having both catalytic converters replaced at 103,000 miles.

I'm running on original catalytic converters at 184,000 miles. It's not an accident mine have outlasted the average ML owners by 50,000+ miles. I'm also on original plugs. That's right. Plugs that came in the vehicle new. Many have suggested I change them, but why? I had them checked by my indy a while back and he said not to waste my money. They were fine. Would they still be there if I burned cheap gas instead of the 91? I doubt it. Dirty burning fuel fouls plugs.

So, back to the basic question. Will I experience problems? The chances are, yes, you will. Will you experience problems if you happen to throw a tank of 87 in it every once in a while? Hard to say for sure, but probably not. BUT, I wouldn't use it, at all, because we all know how habits are. You'll do it once, not see a detectable loss in power or mileage and then you'll do it again. And, before you know it, that's all you use.

Each owner is in charge of their own vehicle maintenance. They will ultimately do what they want, which is why buying a used car is so risky. You don't know how well the previous owner followed manufacturer recommendations for oil changes and gas usage. I wouldn't want to purchase a used MB that I knew the previous owner burned 87 in it. But, that's information you'll never be privy to.

So, based on the information I have and the damage I have seen, firsthand, to engines that required 91 minimum and the owner burned 87 in them, instead, I would say that you take no chances and burn premium fuel.

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post #14 of 17 (permalink) Old 05-13-2008, 08:34 AM
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Originally Posted by mlfun View Post
Mike, Jay, Cmitch,

Melissa asked "Would there be any problems ... ?".
None of your replies addresses that question.
I think the same applies to your replies as well. Even more usless than others...

Don't believe everything you think
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post #15 of 17 (permalink) Old 05-13-2008, 10:27 AM
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You can try it yourself, if you have lower than premium gas in your tank right now, drive it consciously , taking into consideration the pickup of your car. Now load it up with premium and you will feel the difference. That's the safest way to go, to go by what the manual says.
On 8 cyl. engines, there are16 spark plugs and they need all the energy your fuel can offer to boost them all.
I guess it applies to all of nature be it a machine or man.

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post #16 of 17 (permalink) Old 05-13-2008, 12:37 PM
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Originally Posted by melissa25 View Post

I have an ML350 and read in the manual that I should only use Premium gas. Would there be any problems if I were to get Plus gas occasionally rather than the recommended premium?

Thanks in advance!

All over the U.S.A. there is a difference in wording.
Premium, Super Unleaded, High Test etc.

Your Owners Manual should reflect the R/ON Research Octane Number.
otherwise known as the OCTANE NUMBER.
Mine is 91 Octane. Should the Gasoline with the Octane Number, not
necessarily the name.

New York City, NY
Richmond County

United States of America
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post #17 of 17 (permalink) Old 08-05-2008, 11:12 AM
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Here's an article confirming most of what I have been saying on this forum about premium fuel.
Hey , there's even a quote from MB.

------------------------------------------------------------- - Why use premium gas when regular will do?
She's right. Engines designed for regular fuel don't improve on premium and sometimes run worse. And today's engines designed for premium run fine on regular, too, their makers say, though power declines slightly. (Background: About Octane ratings)

But premium lovers are passionate. "I would simply curtail driving rather than switch grades," says Bill Teater of Mount Vernon, Ohio, who puts high-test in both his Cadillacs, though only one recommends it. He's sure both the DeVille and the Escalade run rough and lack pep on regular.

Prejudice and preference aside, engineers, scientists and the federal government say there's little need for premium.

"Generally, the more expensive the vehicle, the higher the expectation for performance and the more the customer is willing to pay for fuel," says Pete Haidos, head of product planning for Nissan in the USA.
The only modern engines that should really need premium are those with superchargers, which force-feed fuel into the cylinders. "You're driving along and just tramp the gas and the knock sensor cannot sense the knock fast enough in some cases," because the supercharger boosts pressure so fast, says Bob Furey, chemist and fuels specialist at General Motors.

Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey.

Automakers say they don't test premium engines on regular to check the difference, but some auto engineers estimate that power declines roughly 5%.

"We can't guarantee the vehicle will perform as specified if other than premium fuel is used," says Mercedes-Benz spokeswoman Michelle Murad. All U.S. Mercedes engines specify premium.

All Porsche engines are designed for premium, too, but it's not available everywhere. "Our cars must be able to drive all over the world, and so we are able to run on regular," says Jakob Neusser, director of powertrain development at Porsche's research and development center in Weissach, Germany. "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.

Premium, in fact, sometimes is worse fuel than regular. It resists knock because it's harder to ignite than lower-octane fuels. As a result, some engines won't start as quickly or run as smoothly on premium, notes Gibbs, the SAE fuel expert.
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