Which is better gas to fill your car up with--Premium or Super? - Page 4 - Mercedes-Benz Forum

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post #31 of 50 (permalink) Old 08-17-2004, 09:07 PM
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RE: Which is better gas to fill your car up with--Premium or Super?

I have a SLK 320 and when I read the article on the Microsoft web site of using a lower grade will get you the same results of a higher grade. Well, I tried the 87 grade and my car ran like crap. I thought I killed my car. The acceleration was bad. That whole week, I was putting in 93 grade in my car as soon as the 87 grade got out of my car. I will never put in anything lower than 91 grade which is recommended on the SLK320.

The bottom line is never put in anything lower than what is recommended for your car.

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post #32 of 50 (permalink) Old 08-18-2004, 01:16 AM
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RE: Which is better gas to fill your car up with--Premium or Super?

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kb13 - 8/15/2004 10:57 PM
I spoke with a chemical engineer who did research on the subject and discovered the only difference between high octane and regular was additives. He said, unless you are experiencing knock, use the lowest octane. They just add additives to the same basic gas to increase the octane level.
For the most part that is a true statement. There is more than one way to make a higher octane fuel and not every company uses the same recipe. The octane rating is really a ratio of octane, the stable component under pressure, to heptane, the unstable component or a mixture that gives you the equivalent performance of that ratio. One thing not really discussed in this thread is the fuel's sensitivity. A fuel with high sensivity would be one that behaves like a lower octane rating under stress. I imagine that this is more of a concern in areas that use RON instead of (R+M)/2. That's because a high RON fuel can have a low MON. That may be why the dealer recommended that Skipper use the 98 rating instead of 95 [based on some anecdotal experience].

Just because you don't have ping or knock, because the engine management system is able to compensate, doesn't mean that the fuel is burning efficiently. It won't burn efficiently and there will be deposits that could cause bigger problems later. This is a cost you won't see right away.

A recurring theme seems to be that using a lower than recommended octane will save you money. Now, how much are your really saving if you use the lower octane? If you live near me, you might see 87 at $2.11, 89 at $2.21, and 91 at $2.31. Most of our current MB's in the NA require 91. Let's forget about 87, it is too low. The difference in price between 89 and 91 is $.10/gallon or 4.5%. Based on some reports on the R170 forum, using 89 degrades fuel economy by ~3%. That gives a net savings of ~1.5%. If you purchased 20 gallons of 91, you would need 20.6 gallons of 89 to go as far. You would pay $46.20 for the 91 and you would pay $45.53 for the equivalent amount of 89. That would be a net savings of 67cents not the $2 you saw up front. Rather than trying to save a few cents with the lower octane, why not up your tire pressure a little and get a gas card, or equivalent, that gives you 5% back on your gas purchase. Plus you'll get better performance and you won't have to be concerned about those nasty deposits.
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post #33 of 50 (permalink) Old 08-18-2004, 08:36 PM
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RE: Which is better gas to fill your car up with--Premium or Super?

Up till 100 I try to find the highest octane I can get my hands on, notmally its 98.
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post #34 of 50 (permalink) Old 09-15-2004, 11:50 PM
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RE: Which is better gas to fill your car up with--Premium or Super?

SledDog,

are you an accountant?

not giving you a hard time - i really enjoyed your analytical approach to octane vs. $$ spent!


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post #35 of 50 (permalink) Old 09-16-2004, 12:48 AM
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RE: Which is better gas to fill your car up with--Premium or Super?

[QUOTE]SledDog - 8/17/2004 9:16 PM

For the most part that is a true statement. There is more than one way to make a higher octane fuel and not every company uses the same recipe. The octane rating is really a ratio of octane, the stable component under pressure, to heptane, the unstable component or a mixture that gives you the equivalent performance of that ratio. One thing not really discussed in this thread is the fuel's sensitivity. A fuel with high sensivity would be one that behaves like a lower octane rating under stress. I imagine that this is more of a concern in areas that use RON instead of (R+M)/2. That's because a high RON fuel can have a low MON. That may be why the dealer recommended that Skipper use the 98 rating instead of 95 [based on some anecdotal experience].

QUOTE]

How would I find out what my fuel company is using? Sled dog, Id like to know more on this type of ratios and what is MON?
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post #36 of 50 (permalink) Old 09-16-2004, 06:42 PM
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RE: Which is better gas to fill your car up with--Premium or Super?

i tried both Premium and Super but found that desiel fuel was still best for my 300SD
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post #37 of 50 (permalink) Old 09-17-2004, 12:21 AM
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RE: Which is better gas to fill your car up with--Premium or Super?

Quote:
FishOmatic - 9/16/2004 5:42 PM

i tried both Premium and Super but found that desiel fuel was still best for my 300SD
I see you're the icebreaker here...a new one too...

[:D]

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post #38 of 50 (permalink) Old 10-09-2004, 03:57 PM
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RE: Which is better gas to fill your car up with--Premium or Super?

Quote:
420SEL Realtor - 9/15/2004 10:50 PM

SledDog,

are you an accountant?

not giving you a hard time - i really enjoyed your analytical approach to octane vs. $$ spent!
Funny.... No because in my world all the numbers really do have to balance[:D].

Blast26, you might check your fuel company's website, some give out info like that, others don't. RON is Research Octane number which is measured under gentler conditions (lower RPM) than MON, the Motor Octane Number. RON is almost always higher than MON.

This is why Storm's comment doesn't apply [;)] (j/k) but really, his numbers are RON and will always sound higher and thus be more impressive[:D] while ultimately the fuel he uses may actually have an (R+M)/2 the same or even less than what we have in the states.

Fishomatic, at least you didn't bring up cetane ratings[:0]. I thought that the 300SD was a 300 from San Diego[:o)], or was it South Dakota?
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post #39 of 50 (permalink) Old 10-09-2004, 04:45 PM
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RE: Which is better gas to fill your car up with--Premium or Super?

alltough your math is correct your thoughts are not, in the uk the fuel here is better quality than the usa which is reflected by the price ( we refine it better ) the usa dosnt really give a shit on emmisions but thats life[:)]
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post #40 of 50 (permalink) Old 10-09-2004, 04:49 PM
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RE: Which is better gas to fill your car up with--Premium or Super?

storms comment does apply here
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