Boulder GT3

It's not uncommon for the track to be out of race gas or not be able to find the guy that can pump it. You head to a close gas station and all they have is regular and that's what you pump. I've done that at Pahrump several times. Unless you're running something that requires race gas like a Radical my experience has been that everything works out ok although the performance drops.

I did pick up a bad load of gas in a 355 Ferrari at Pahrump when I was tracking it. A crisp $5K to fix the cats.

Two motors I've seen apart that had run on regular a lot. The first is a 4.4l out of a 2005 Range Rover. Probably pretty similar level of tune compared to a 350 benz. I know the owner and she never ran premium. An oil pump failure killed it but the heads and tops of pistons were clean. The second was a tt that the guy had sometimes run regular at track events and no damage there either.

I had a white paper on fuel octane I'll try to find. The net is, race gas in a car that isn't tuned for it can generate some heat.

Benz-O-Rama

A little off topic:

Suppose someone has an E500 with a 93 octane ECU tune. Meaning, don't even think about running anything lower than 93. Let's also say that this person has, available to him, CAM2 racing fuel. Is it safe to run a much higher octane in a car that's not tuned for it? Or is it possible to grenade your motor?

I can't remember what octane this particular flavor of CAM2 is, but it's available at a Sunoco station near me. I wanted to try it but I'm skeert!

Polar Bear

Should be OK if it is unleaded, but I don't think you will really see much performance benefit, it any. It will just smell better out the exhaust!

If you had forced induction and the right tune, a huge difference could be realized.

220S

Octane is burn resistance; so at higher compression and temp that means much less chance of pre-ignition and/or detonation. Higher octane then higher compression rates are allowable.

And if you're tracking a high compression motor, keeping it at max rpms, then it's imperative for cooler burning and no detonation (or pre-ignition) issues.

Depending on your compression ratios, you either benefit or you don't. That's why there are several levels of octane ratings (and there are different ways to rate octane, too: motor octane, research octane.) And higher compression motors will run COOLER on higher octane, NOT hotter. Even if it's your street car. High octane simply means it won't burn as readily when the motor's hot, and the fuel won't tend to burn improperly. And that's its resistance to burning. It won't burn as readily as low octane will. Not until it meets the proper source of ignition (ie sparkplug) along with air mixture.

High octane on a low compression car is not harmful, it's simply a waste.

All sanctioned track events will have adequate fuel available. It's such a rarity that you have to actually leave the track to go get gas. Doesn't help you much during the event that's for sure. Unless it's a small club event that has rented a track and nobody's prepared.

Tracking a car on regular means you're contradicting the purpose of being there in the first place. And your car is running hotter at those high rpms.

We all agree that running low octane on a few occasions will not destroy the car. We all agree that the motor's DME will help prevent fuel burning issues. The question put forth was is it okay to run regular as a fuel in a motor spec'd to run a higher octane. And the answer is why?

As for the Range Rover, well good for it. I'm sure the performance was pretty limited, and she drove it like a mouse. The DME rescued it and therefore you see no damage to the top of the pistons. And if it was as clean as a baby's bottom, then their oil is tight and there's no coking/carbon buildup from burning oil residue, either. And who really knows the history, the mileage, the driving conditions, the driver's habits, etc..

220S

Benzo, cam2 is 100% octane. No issues whatsoever. Except it's expensive and as PBear says, you won't really notice (unless you are really keeping up the rpms.)

I sometimes will do a mix of premium and 100% in my P-car. It makes me feel good

ejsheltra

I had been told the same thing by the local Bobby Rahal dealer in Pittsburgh Pa that the 08' and09' models will run fine on regular. The compression is set low enough and the antinock sensors control to a wider range than in the AMG tuned performance motors. Polar Bear is right. The man is asking a legitimate question. At least give a decent and intelligent answer.

Vik888

If anyone can get a dealer to put this in writing to them, I would like to see a scan or faxed copy of it.

What some sales guy said to so and so, is all hearsay.

Polar Bear

I have checked two 2008 cars and the ECU is indeed set to 87 octane. Two things to note - 1. This settings would not exist if it were not meant to be used and 2. It is defaulted now to 87 so perhaps the salespeople are accurate about this. But I do know from experience that changing this setting to 93 octane makes the car get better mileage and have better drivability, so I think it's a no brainer to get better performance and economy by running the better grade fuel.

I don't have access to a 2007 or older to check to see what the timing is set to on them. Perhaps the salesperson is right - they have changed the factory default settings for ignition timing on the newer cars. I know that Cadillac started allowing regular fuel so perhaps MB decided to do the same thing.

I don't have an owners manual to review to see if the wording has changed from "required" to "recommended" on the 2008+ cars.

I looked at a Volvo S60 at one time, and the dealer told me the cars run just fine on regular fuel, without me asking. The filler door did say premium fuel recommended, and this was a turbocharged car even. If I had bought it I would have only have ran premium, but I do find interesting the conflict of information.

Vik888

Are you saying my 08 E550 is set to 87 and I should have the dealer change it to 93 (although 91 is premium in socal) since I only use premium?

Thanks!

Carl Lassiter

Depends on the engine. Most German car makers say run 91 minimum to protect themselves. I run pigswill-grade 87 in my truck as it's only making 380bhp/402lbs. I'd perhaps adopt the same approach with the 500 or 350 engines from MB, unless I was planning on stringing it out long and often. I'd never run less than 91 in an engine that runs beyond 6,500rpm and had a high specific output.

This being said, 91/93 will never hurt matters.

dvmak

Yeah, Volvo has/had a few different engines. The one in My S80 is Volvo's own I6 and that they say needs premium but then on the S40 and perhaps even the S60 they sourced (Think it's mitsubishi) and allows for regular.

On the Cadi CTS they recommend premium if you want to get the 304HP otherwise regular is fine ...

Polar Bear

I am not sure if the E550 is set the same as the E350 and C350, but I would have them check. I think 91 octane is a setting as well.

But yes, I would have them check. It is in SDS under Control Units --> Drive -- > Motor Electronics -- > Control Unit Adaptations --> Ignition timing (off the top of my head).

russianczar

If we decided to buy a MB, we need to treat it as such, my e320 likes gas only from premium Gas stations, otherwise it starts acting up. So I think it is only fair to say that extra 20 cents per gallon is better that thousands at a MB dealer to repair the damage.

dvmak

Polar Bear,

I'd have to somewhat disagree with your earlier post that "premium has better cleaning effects on the engine" ..

I definitely agree that premium should be used to get optimum performance but cleaning additives aren't necessarily the same in premium gas. There are differences in the additives used in premium stations like Shell vs some no name station and the price probably reflects such.

So you may get premium from a no frills station that has less cleaning additives then say regular gas at a Shell station .. IMHO ..

Polar Bear

Yes - I agree.

reyzbenz

Article from Mercedes-Benz Anaheim E World (http://www.imakenews.com/mercedesben...71kky,b9pRh4VT) January 9, 2009
What Grade Do You Give Your Engine?
By the way, this is no “knock-knock” joke!


You pull up to the pump and usually have three choices: Regular, Mid-grade and Premium. Are these grades the equivalent of “good, better and best?” Have you ever been tempted to give your car a “treat” and upgrade? Do you really have to feed your high performance car that outrageously priced Premium grade?

These questions are not “fuelish,” and the answers are based on something called the octane rating of gasoline. The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. This is meaningful when you recall how a four-stroke, gasoline-fueled engine works. One of the strokes is the compression stroke where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a sparkplug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. High performance engines generally have a higher compression ratio. Higher octane fuel can better tolerate the greater pressures in high compression engines.

When gas ignites by compression rather than because of the spark from the sparkplug, it causes a condition known variously as knocking, pinging or pre-ignition. Knocking generally occurs when climbing steep grades, rapidly accelerating or driving at unusually high altitudes.

Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like Regular-grade 87-octane gasoline) can handle the least amount of compression before igniting. So, the compression ratio of your engine determines the octane rating of the gas you must use in the car.

The gasoline grades have corresponding octane ratings, typically 87 for Regular, 89 for Mid-grade and 91 for Premium with slight variations around the country. Most filling stations sell three grades, but some offer a few more choices between Regular and Premium. Even so, the typical gas station has just two underground storage tanks. Midgrade and other octane ratings are created by blending these two at the pump.

The basic question we want to answer is, “Should you consider spending the extra money for Premium gas?” The answer is a qualified, “No.” The fact is, for most car and truck engines, Regular grade 87 is fine.

That’s good news, but what if your owner’s manual recommends Premium grade fuel? The key word is ‘recommends,’ which really means it’s okay to use Regular under most driving conditions. Virtually every expert – even those from oil companies and auto manufacturers – say that using Regular will not harm engines, but you’ll probably not get the ‘advertised’ performance. In other words, you may add a second to the zero-to-60 mph time a reviewer said you should expect from your car. Again, using Regular gas will not damage the modern engines of most of today’s cars.

Modern engines with advanced computerized engine management systems rapidly adjust their ignition timing at the first indication of knocking. For this reason, using Regular will not void your manufacturer’s warranty unless, in the rare case, your car’s owner’s manual states that Premium grade gasoline is REQUIRED. The owners of high performance engines that require the highest octane are well aware of this fact because high performance was an important factor in choosing their particular cars.

However, if you own a “classic” car or a vehicle that is 10 years old or older and lacks such stuff as electronic fuel injection, computerized engine management and knock sensors and the owner’s manual specifies Premium grade fuel, DON’T USE ANYTHING OTHER THAN PREMIUM! If your vehicle has a supercharger and you drive aggressively, you might also want to use Premium. In this latter scenario, knock sensors cannot sense the condition fast enough because the supercharger boosts pressure too quickly. Of course, if your engine does experience knocking, no matter what vintage or sophistication, feed it the next higher grade of fuel or bring it in for a diagnosis and possibly a tune-up.

Using Premium grade fuel in a vehicle designed to operate on Regular is a complete waste of money. It won’t add to performance since the engine is not designed to make use of the higher octane. Don’t believe that bunk about Premium gas doing a better job of keeping an engine clean. All grades of gasoline contain detergents and additives intended to promote clean combustion.

ohlord

the op's question?
"Other than that, are there any long-term negative effects?"
if not. Yes there are long term effects.The dealer can pull up the engine knock data and void the warranty if you end up with one of the other long term negative effects.A big hole in the crown of a piston.Use premium.Or are you a gambler for 20cents a gallon savings?
Which I figure comes out to be less than 200 bucks a year at 1 fill per week.
If you need to worry about 200 bucks spread over the next year
Maybe as some have suggested a different Make car is in your future

BobbyT

Thanks, ohlord. I really don't have to worry about 200 bucks spread over a year, being something of a plutocrat, but I didn't get this way by ignoring details and being reluctant to ask questions. Comments such as yours notwithstanding, so far no one has weighed in with any hard data on engine damage or voided warranties.

220S

Call MB-USA yourself.

I just called them. Here is MB-USA's position: "If it is determined that using a lower octane fuel than what is recommended by MB-USA is promoting or has caused any damage to the vehicle, then MB-USA has the right to deny a warranty claim and or repair."

This doesn't mean that they will automatically deny an engine repair warranty claim, but if the ECU records a change due to octane, or if they feel that you have voided your warranty, then you are taking a gamble. Have fun in court.

So it's up to you, folks. I'm under warranty and I plan to use the recommended octane. If you want to take the chance while under warranty and save a few bucks on fuel, then by all means do whatever floats your boat.

vettdvr

I use Prem 93 in my E500 and even though my boat will run 87 I use 100 gallons of 91 in it due to the loads and full throttle operation above 5000 rpm consistantly.

So this is what floats my boat.

timeskew

Is there an easy way to learn what my car is set to? Self-diagnostics? Or must I go to a dealer to find out?

dvmak

BobbyT,

You can't seriously expect a black and white type answer on this topic. This is a discussion rehashed in just about every car forum around and many so called experts have their own opinions on both sides of the fence.

The bottom line is that there is a knock sensor that will COMPENSATE for running regular. I highlight compensate as this should set off an alarm. Just becasue the engine can comensate doesn't imply that it's not having some adverse effect in the long term .. IMHO.

What are the long term affects? Could be slight damage to the catalytic or other emission systems. Maybe the pistons are worn sooner ... maybe if you only put average miles on each year or trade every few years .. you would never realize the 'damage'. The next guy who buys it will have to deal with that!

it's your car .. do what suits you .. personally I bought a premium car and want to realize the slight performance advantages that it supposedly holds over other cars .. so I run premium and replace with OEM parts ..

akbro93704

whenever we have had C-class loaners (C230 V6's, C280s), I've noticed they ping like CRAZY because people just put 87 in them. Yes, these cars have knock sensors, but they can't stop all the pinging. SO, USE PREMIUM!!

Scott E350 Saks

That is very much the truth. When I was shopping for my 2nd Benz, I couldn't begin to tell you how many told me it had Xenon lights only to get to the dealership to find it hadn't. That's when I learned--on my own--Xenon only came in PII or Saks packages.

To the question. The cost to run premium over the other is very minor. Stay with the premium and take care of your engine/performance.

Untertürkheim

It often costs less to run premium once you factor in the decreased fuel economy of substandard fuel. Once the voided warranty is factored it, it IS cheaper.