Discgolfer74

When I picked up my car in Phoenix and drove 1900 miles back to Ohio, I noticed a BIG difference in Octane ratings for Premium Gas. It ranged from 90 Octane to 93 Octane here in Columbus. Our Plus (midgrade) rating is 89 Octane. Due to the high gas prices, I've been mixing my fuel, half tank 89, and half 93.

Does anyone know what the Octane requirements are for our MBs?

I also would like to hear what Octane you guys (and girls) are putting in your cars.

whoover

91. 90 is standard in the mountain states because the car gets less air, but anything lower than 91 at sea level will lower performance when the knock detectors retard timing.

rsatmans

93 after i bought that chip from speedtuningusa. Not a problem to find in georgia

rbpeirce

My 2007 CLK 350 calls for a 95 Research Octane Number (RON) with a 91 minimum. Our gas averages Research and Motor, and the spread is 8-10 points. Therefore, you can easily get away with running 89. It will have a RON of 93-94.

I did it for years on an NSX I was tracking and I have been using 89 in my MB and my wife's RL. There is the possibility you are not getting all the horsepower your engine can generate, but I doubt you will notice it. Further, modern engine management systems can easily deal with such a small difference. Finally, 89 is $0.10-0.20/gal cheaper than 93, which is overkill.

I haven't tried it, but I am told you can easily get away with running 87 for relatively short periods, but I don't know how short.

Discgolfer74

So, I should be fine if I keep doing what I've been doing, 50% @ 89 & 50% @ 93? I just want to make sure I'm not gonna mess anything up.

rbpeirce

I am saying you can use 100% 89 without any problems, assuming your car has the same requirements as mine, 95 RON with a 91 minimum. Most 89 you are likely to encounter in the US will be at least 91 RON and probably 93 or 94.

Musikmann

I think your math and method are both fine. MB specifies 91 and that's what you are using with the 50/50 blend.

Discgolfer74

Thanks for the feedback guys! This really helps!

aznAMG07

I use 93 octane. I thought about going bold and use E85, which has an 101-105 octane, so it can yield more power. However, I haven't done much research about it on the MB yet.

rbpeirce

My CLK 350 is supposed to use 95 with a 91 minimum. Other models may be different. However, MB specifies in terms of Research Octane (RON), which is 4-5 points higher than what you read on the pump. The pump octane is the average of Motor and Research.

The 89 we see on the pump has a RON of 93-94 or maybe more, and the 93 is 97-98. A 50/50 blend would have a RON of 95-96, which would be more than enough for my car. However, I have never had any problem running 89 in any high performance car requiring "premium".

I recommend the OP at least try a couple of tanks of straight 89. I doubt he will notice any difference, but if he does he can go back to the 50/50 blend.

Discgolfer74

I might try 89 on a couple fills, as long as it won't damage anything. That could save me a lot of money in the long run.

GGM

What Math are you using to get your savings? Factor in the drop in miles per gallon and you will be lucky to break even. What is the price difference between 89 and premium (either 91 or 93 depending on where you live)? If it's still the .10 a gallon it used to be (or even .20) you have to figure the percent difference.

Just to use round numbers, say the price difference is .20 per gallon on 4.00 per gallon. That's a 5 percent savings. If you average 25 miles per gallons on premium and your mileage goes down 1.25 mpg on 89, you break even. Any more mileage loss and you are actually spending more for gas when you use 89.

Why anyone would buy a Mercedes and put anything other than premium makes no sense. You have invested in a well engineered car which functions best on premium fuel. Anything less actually costs you more money. You're talking about saving pennies. In absolute terms, it seems like more, but it really isn't when you figure it in percentages.

This scenario is subject to change as the price differential goes up. But the price differential would have to increase substantially for there to be any savings. But as the overall price goes up, so the differential also needs to increase by a larger factor in order for there to be a savings in using anything other than premium.

I hope this helps.

rbpeirce

If you are running the correct octane, increasing it will not help in performance or mileage. Some people think higher octane gas then required by the manufacturer will improve engine performance. It won't. It just wastes money, and nobody, not even an MB owner, should do that

Note, I am not saying you cannot modify an engine to get better performance on higher octane gas. I am talking strictly out of the box.

I have driven many different cars over the past 50 years and tried "better" fuels. I never found that it made a measurable difference on the road. The one exception was when my 1977 6.9 developed a vacuum leak and started to knock on regular. I had to run 89 until I got it fixed. However, running 89 did not improve mileage or performance. It just stopped the knocking.

Discgolfer74

I agree. Granted, I would only save about $1.60 per fill-up, which is no big deal. But over the course of a year, that could add up to $100. I drive 200 miles per week just to work and back, which doesn't included weekend trips to play discgolf, or to visit the in-laws.

I'm not saying that I'm broke, otherwise I wouldn't have bought a MB. But I'm just the type of person that will bend over to pick up a penny whenever I see one. Pennies add up! Last year, my saved change added up to over $880, which paid for a weekend away for my wife and I in Chicago. This year so far, I've saved over $750 in change, which will contribute to our upcoming vacation in the Keys.

Plus, the more money I save, the more I can MOD my Benz!

M-bENZ

[QUOTE=Discgolfer74;2855091]I agree. Granted, I would only save about $1.60 per fill-up, which is no big deal. But over the course of a year, that could add up to $100. I drive 200 miles per week just to work and back, which doesn't included weekend trips to play discgolf, or to visit the in-laws.

I'm not saying that I'm broke, otherwise I wouldn't have bought a MB. But I'm just the type of person that will bend over to pick up a penny whenever I see one. Pennies add up! Last year, my saved change added up to over $880, which paid for a weekend away for my wife and I in Chicago. This year so far, I've saved over $750 in change, which will contribute to our upcoming vacation in the Keys.

Plus, the more money I save, the more I can MOD my Benz![/QUOTE]

Thats what I do too...anyway back to the gas thigns I cant find no 93 octane around here so I have to use a premium 91.

Discgolfer74

This was the best answer I got to explian this:
So therefore, in the states where the car would get more air, the Octane level would be higher.

aznAMG07

Higher octane produce less knockings, which means more power only if the car is prepped for that.

As GGM said, MB recommended it for a reason whether it maybe for a profit or real advice. This is comparable to engine oil. Why don't you save a little and get cheaper oil than use recommended synthetic one or downgrade cheaply made tires than use performance tires? Why do some people prefer certain manufacturers to others? Gas might be gas in the end, but it depends on how the company refined it. Higher octane is used for high performance cars because it produce less knocks, which means it can run on a more aggressive set-up/tune; therefore, the car produces more power. Sure you can run lower octane, but you won't be at 100% power most of the time. Most people who drive their car don't really care much about the specifics. For car fanatics, these little detail can be major. I for one will never put anything that is less than 93 octane. Then again, it's the owner's car, and he/she can do whatever he/she wants to it.

Discgolfer74

That really puts things into prospective for me, which makes for a difficult decision to make; saving a few bucks vs peak performance. Geez, I'm so indecisive. I am such a penny picher, yet the reason I bought a 500 was for the power... I guess it really depends on what is more important to me. Well, since the only time I drive like a grandma is when my daughter is in the car, I guess I'll save on MPG then.

GGM

I never said to use higher octane than recommended. Mercedes recommends "premium." Here in Orlando, "premium" is 93 octane. In my travels, sometimes "premium" is 91. Either way, I use "premium."

My experience with gas mileage comes from my wife's Chrysler 300 with the 3.5 liter engine. She used to run regular in it because it was cheaper. I then tried the recommended midgrade and compared the mpg she was getting with regular vs. the mpg with the midgrade. She got about a 10% increase in mpg vs the less than 10% price differential between regular and midgrade. So she is actually saving money by spending more for midgrade.

I have never tested using a lower grade gasoline in my E350. I get better mileage than she does and I don't want to mess that up.

I believe manufacturers make recommendations based on the engineering of the engine. I don't think there is any ulterior motive.

Just sharing my experience. YMMV

rbpeirce

The only thing I can disagree with on that is that MB uses RON and our pumps use the average of Motor and RON. My CLK350 actually recommends 95 RON (with a 91 minimum), which would be 90-91 pump. I use 89 because we don't have 91 in my area and 93 is overkill. My 6.9 calls for regular.

As for mileage, my CLK gets 30, believe it or not, running 75 on I-81 through the Shenandoah Valley but only about 22 in the mountains of Western PA. If I could actually find 90 or 91 pump octane, I wouldn't expect to do much better.

The 6.9 seems to get 10 city and 14 highway no matter what I run, which suggests 87 actually is about right. Can you believe that, 10/14!! What a waste.