It's doesn't really burn faster, if anything, lower octane burns slower. What makes your car consume regular faster than premium is if the ECU detects a knock it will pull back timing and enrichen the mixture. At this point you'll start losing fuel mileage probably beyond the 5% or so you are saving at the pump. Of course you wont know it from your MFD read out of mileage, you'll have to calculated it manually to see if there's a difference.

 

 

If you want to be a proud owner of a luxory-car fill it up with premium, you guys start complaining when gas prices go up a couple of cents. Here in Europe we almost pay the double for gas. But for my car that runs on fuel I fill it up with 98 octane and we just have one kind of diesel so the car that runs on diesel can't choose. So stop whining or sell your car. The higher the octane the smoother the engine runs, the more miles you can make per tank so if you fill it up with lower quality you will loose on the milage. One way or the other you keep on paying the same amount. If you don't make more miles with higher octane, it just means that you use what your engine has and you should have always bought premium.

 

Let me repeat my post, as this still seems to be a discussion:

I know this debate keeps coming up and I keep wondering why? Why do people keep asking about gas prices, can I use mid-grade, regular, blah, blah, blah. Guys bottom line, and research proves this: Use what gas is intended for your vehicle. If you have a Benz, across the board on any Benz it says Premium of 91 octane is required.

Required is not a suggestion, recommendation, or anything up for debate. It is required. This should end this debate, or any other questions surrounding it, and others have posted pics and sources as to why.

If you cannot afford Premium gas, or if it is hitting you that hard, then other alternatives are needed, the first is to possibly sell your Benz to someone else. JK, but all jokes aside, I am not being insensitive, or a jerk about it at all, but why would you abuse or attempt to abuse your car? You spent a premium price on the car, and you should know what was attached to it.

Take care of your car, and hope gas prices will come down some. All I can say.

 

From the owners manual (see below) -And if this isn't enough to scare you into not using regular I don't know what is.




Now the only exception MIGHT be if you change the ECU settings to accept the crappy fuel and accept the reduced performance.
Buell posted on that a long time ago. I had been considering trying it, but
since I'm running OVER boosted, it's likely not a good idea + the amount of money I've spent to increase performance would be a waste.
Still, I have a guy down the street that likes to tinker, digs what Ive done with my car, and has a SD system. (and occasionally will do a hook up for free if I bring cold GERMAN beer)
I'm curious to see what would happen, but I think it might be better to try on a stock car.

 

I drive 310 miles per day in my C280 and in my experience with my C-cvlass that is not true. I have found it to be absolutely true in another car I own, which is a high-performance ride, but not in the C-Class where my day consists of

-300 highway miles, 10 city.
-Mostly flat ground with a short stint thru a mountain pass
-Speeds 65-70 mph depending on the limit.
-Always using cruise control.

MPG over the morning trip is consistently 34. The return trip in the evening, with a typical headwind coming from the coast, I get 30. Doesn't matter what gas type. I've tried premium (we only get 91 in California) for extended periods and unleaded for the same. No diff in mileage. No pinging *if* you leave it on cruise and let the computer do the throttle management.

Where there is a difference is if you need to accelerate out of a situation. Doesn't happen often but the reason I drive a Benz as a commuter car is for the sake of safety in that uncommon, unsafe moment... and getting flattened because I can't get out of the way of something big is counter to that principle.

Asked one of the mechanics at my dealership about this. He told me they run 89 in their cars with no ill effects.

Not taking a position either way on this. Just throwing out some info to chew on.

 

Of course they do this, the dealers are cheap *******s just trying to sell cars. They don't care if regular gas will cause any type of carbon buildup or long-term future damage...by then the car will be sold and it won't be their problem.

I would never go by what the dealer says. 9 times out of 10 they have been dead wrong about a problem or any question I had about my car and I have had to later prove to them why I am right.

 

Honestly that just sounds like negligence to me. Talk about possibly causing damage to your product inventory.

 

I would be hard pressed to argue that a dealership for any marque is loaded with product experts.

Like I said, just throwing that out there. I ran some tests on mpg over a few hundred miles and it was a wash over a long set course.

 

i have run only regular (87 octane) since November. No problems, no noticeable difference in performance. I wont fill up at the 10% ethanol stations though. MPG suffers pretty bad with that stuff

 

Have you guys heard of hypermiling?
http://www.hypermiling.com/
I started doing it this week. My normal commute is about 25 miles one way. Depending on how fast I drive I get anywhere from 26 mpg to 31mpg. Using this method for the first time I got to around 35.3 mpg. I tend to stay in the slow lane and follow large trucks/suvs closely also to help. I drive a 2003 c320 by the way.

 

Ha, thats how I've always driven, well I do at times LIKE to drive agressively, but it drives me nuts when I get behind someone who's constantly applying the brake instead of coasting.
If I see the light is red I try to coast, and hope it turns green and the cars start moving so I don't have to stop.
If I see traffic slowing down (and no way around) I'll reside myself to just taking my foot off the gas and coast. Nothing new there.

Coming down the backside of hwy17 (about 1200 ft elevation)
I try to coast as much as possible, just keep my foot away from the gas pedal, and the brake unless I have to.

On flat if I can just set the cruise control and forget it, I can
get the best mileage....but there's always some dumass moron in the fast lane going 50 and I am forced to slow down and speed up which eats gas.

Of course other times I like to haulass and to hell with the gas!

 

To me, it's still about taking care of your car. Taking care of your engine should really be top priority over saving a few dollars. That savings will never equal the potential costs of, though maybe highly unlikely, engine repairs.

Your engine is worth much love and tender loving care. It should be fed the right thing, always.

 

I might be wrong but I feel like all the gas in NJ has 10% ethanol, so I wish I could avoid it but I probably can't.

Does anyone know if this is true, or if there are places to get gas in NJ that doesn't have the ethanol?

 

I also do something else I rarely hear mentioned to save gas. I'm not sure how much it saves if anything noticeable, but I always put up my rear sunshade, close the sunroof cover and put in an MB sun reflector in the front window when parking in sun. Also leaving the sunroof tilted open helps a lot to keep the car cool. When you return to the car, the cooler it is, the less the air conditioning has to work to cool down the hot car and thereby saves some gas.

 

for the people worried about gas, have you considered using e85? (depending on your model year)

 

E85 is not an economically wise decision. Ethanol has about 30% less energy per gallon than gasoline which means your vehicle will eat a lot more of it to go the same distance.

I use 91 exclusively in my overboosted C230K. I'm not worried about $2 on a $50 (higher now) fill up for the peace of mind for the next 40K miles. Changing your driving habits; combining trips as well as the other techniques mentioned here or simply driving less have a huge affect on fuel consumed.

Also, I'm not so sure about the safety with hypermiling. In an emergency situation, you won't have your power brakes, abs, or power steering.

 

I have decided to stick with premium 91 octane (wats a guy gonna do). I need to know what rpm to stick at 2000 through perhaps 3000? I have been getting 29mpg. Will like to bump that to 35.

 

I think you been getting good mpg. Mine is like 21 mpg or so.

 

Only way to do that is trade it on a C230.

 

Uh, thats REALLY good imo for a c320. Shed some weight? How are you gettin 29mpg anywhoo?!

 

Mostly by insisting on going 65mph when I can help it and only going to 70mph to overtake or when I am tired of someone breathing down my neck. At 65mph I am usually at 2500rpm.

Throw in some coasting to stop signs and keeping my distance so I do not have to brake and accelerate all the time.

Hard acceleration has also gone out of the window.

BTW I have no weight to shed. Only a jacket on the trunk.

 

lowest rpm in your highest gear

 

:eek thats really good. at best i can average only 24-25mpg on a 50 mile trip. but i'm usually going 80mph or so.

 

There is no clear answer to your question since lower revolutions per minute equal less piston cycles which means less gas being injected into each cylinder.



I can't imagine getting 35mpg from a car weighing 3500 pounds being motivated by 6 cylinders at 3.2 Litres of displacement. Also, 3 valves limit breathing potential and SOHC limits variability of valve timing. Furthermore, a twin-spark plug setup in the combustion chamber doesn't help with efficiency.

For reference, imagine just under 1 1/2 (2 litre) coke bottles and that is the size of the combustion chamber. Also, use a gallon milk jug to get a feel for visual reference and the weight of fuel used.

29mpg is quite a feat. The only way to get 35mpg is to drive downhill with a tailwind for a couple hundred miles.

For best MPG,

ALWAYS use cruise control on highway set to 65 max

pump tires to 40psi,

make sure the car suspension is properly aligned

Set tranny to WINTER mode

Use Denso Iridium Power spark plugs (change every 30k)

Change tranny fluid every 50-60k with Redline ester based fluid.

Check the health of your 02 sensor both primary and secondary. The 02 sensor determines whether your engine runs rich or lean. Worn 02 sensors lower gas mileage by running the engine rich even if the CEL doesn't come on.