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Gas octane ratings

5K views 32 replies 14 participants last post by  cmitch 
#1 ·
I would like to see what you are running in your new ML's. Please let us know what ML you have, and gas octane ratings you run.

I have a ML350 and run high octane, super. Most of the time I run Shell V-power.

Has anyone seen a difference using middle grade vs. super?
 
#27 ·
OK, Here's what I've been doing:
At about 1/4 of a tank left, I first put in about 5 gallons of mid-grade 89 octane. Then I fill the rest of the tank up with premium 93 octane (usually about 7 gallons). My mileage with all 93-octane premium is around 20MPG. With the mixture I mentioned, I get 3MPG better. I never hear any knocks, and on average I guess I'm hitting the recommended 91 octane so I'm probably OK. I haven't tried using the substandard scum-sucking 87 octane regular that the peasants use, but hey I do save about $.80 per tank with my mixture, plus I get 3MPG better.

Any ideas why an overlal lower octane results in better mileage?
 
#28 ·
wvcox1 - 9/9/2005 1:33 PM

OK, Here's what I've been doing:
At about 1/4 of a tank left, I first put in about 5 gallons of mid-grade 89 octane. Then I fill the rest of the tank up with premium 93 octane (usually about 7 gallons). My mileage with all 93-octane premium is around 20MPG. With the mixture I mentioned, I get 3MPG better. I never hear any knocks, and on average I guess I'm hitting the recommended 91 octane so I'm probably OK. I haven't tried using the substandard scum-sucking 87 octane regular that the peasants use, but hey I do save about $.80 per tank with my mixture, plus I get 3MPG better.

Any ideas why an overlal lower octane results in better mileage?
I used to mix 89 and 93 until 91 became readily available here. I experienced no problems ( 91 is mixed at the pump by combining 87 and 93 in the right proportions ). MB has a min. 91 recommendation on my ML.

As for your mixture, 91 may be the optimum rating of fuel to run in your car and you would probably be wasting your money if you bought 93. I wouldn't go under the 91, though.
 
#29 ·
It's interesting to see the varying ratings from posts around the country. Here in North Texas I've only found 87, 89, and 93. I've used the Shell, the Chevron, Exxon, and other independent stores but they all stick to those ratings, no '91' rating gas to be found around here so far... I guess I'll keep mixing as it doesn't affect my performance, I actually get better mileage, and I'm closer to the recommended 91 octane by doing it that way.

How about this question; does running at an octane rating of 93 cause any issues when '91' has been recommended by the manufacturer? I would think that higher is OK but what would be the implications from an engineering perspective?

Thanks,
Walter Cox
 
#30 ·
I just would not worry about mixing gas to save 80 cents a tank. Thats too much remembering to fill up a car's tank. I am just fine using the 93 octane. I guess its just me.
 
#31 ·
In the August edition of Car and Drive magazine, Larry Webster had an intersting article about gasoline. This article references a standard adopted by several automobile manufacturers for gasoline sold in the United States. Following is the link for the article on line.

http://www.caranddriver.com/article.asp?section_id=27&article_id=9752&page_number=1
 
#32 ·
wvcox1 - 9/10/2005 7:36 AM

How about this question; does running at an octane rating of 93 cause any issues when '91' has been recommended by the manufacturer? I would think that higher is OK but what would be the implications from an engineering perspective?

Thanks,
Walter Cox
91 is the MINIMUM recommendation by MB. 93 should not cause problems, even for a car where only 87 is recommended. As I stated before, if your performance doesn't improve moving up to 93, then I'd stay with the 91 since it is probably the optimum octane for your car.
 
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