fuel requirements - Page 2 - Mercedes-Benz Forum

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post #11 of 15 (permalink) Old 03-04-2011, 03:42 PM
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Originally Posted by gyrate View Post
you are not going to save money on lower octane so why wouldnt you use 93?
What are you saying? There is no price difference? Typical 20 cents per gallon between mid grade and premium in our area and as was said above, no noticeable difference in mileage or performance. So how do you say "you are not going to save money on lower octane"?

I'm not saying that is true for all cars, but at least for some.
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post #12 of 15 (permalink) Old 03-04-2011, 04:14 PM
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Originally Posted by gforaker View Post
What are you saying? There is no price difference? Typical 20 cents per gallon between mid grade and premium in our area and as was said above, no noticeable difference in mileage or performance. So how do you say "you are not going to save money on lower octane"?

I'm not saying that is true for all cars, but at least for some.
In my case, I get BETTER mileage with mid-grade. There I said it again--BETTER! And again I say: It's not a cost thing, it's a performance thing. The mileage is better and other factors such as temp and oil consumption remain the same.

Of course your mileage may vary. Burn what makes you happy.
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post #13 of 15 (permalink) Old 03-04-2011, 04:14 PM
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simple version? they are full of it.

if you have an ancient car that runs like crap you wont tell. if you have a proper running motor, you will syphon it out 20 seconds after you pour it in.

but what do i know

mid grade can be a fair compromise for some motors. not all but some. but 87 makes premium only vehicles run bad.

vw phaeton. when vw copies mercedes, but forces you to service it next to golfs and jettas

Last edited by gyrate; 03-04-2011 at 04:17 PM.
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post #14 of 15 (permalink) Old 03-04-2011, 04:32 PM
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Originally Posted by 300E91 View Post
Myths about premium gas continue. The only thing octane does is increase the compression threshold of the fuel before detonation. The detergents and other additives of a brand are the same across the grades.

In a previous post I cite various experts on octane, including Mercedes, Porsche and SAE engineers.
Each agree that octane is not such a big deal. A Porsche engineer comments: "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.

After a long period of comparison testing, I have found that my M103 engine runs better on mid-grade than the specified premium--better mileage and identical operating temperatures and oil consumption. For me it's not about the cost but the performance.

This is a debate that won't die. Burn whatever makes you feel best. If you're curious about the reality, set up a spreadsheet and run some comparisons.
Maybe you will not notice the lower performance on 350 HP Porsche and measuring 0.01 sec difference in acceleration is a deal on its own, but in the past, when our family car was 4-banger Volvo, I was filling it up with Premium for going to Sierra even the car should run on regular.
Having Premium would allow the engine to take lot of grades without downshifting. I never liked to grind the engine at 6000 rpm for 1/2 hr so the 25% more expensive Premium (at the time) was money well spend for me.
Bottom line, with small engine run on Premium I could definitely tell I am getting there faster.
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post #15 of 15 (permalink) Old 03-04-2011, 06:06 PM
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When I use to deal with small engines, I mean small like on Argos and smaller bombardier vehicles the biggest killer to an engine was "regular" gas. Maybe it has to do with tiny welsh plugs on the carbs and tiny jets but you could always tell the difference between two identical carbs run on regular vs premium. Reg carb would be varnished and fuel tanks full of sediment. Prem carb would be much cleaner and significantly less varnish on welsh plugs and jets and floats and the fuel tanks had less sediment. Oh, yeah if they are the same why do they taste different, additives? nah

The mid grade makes sense, again, higher octane rating, less detonation. Could very well be a sweet spot or "room for error" thing with varying quality of fuels between countries. Again, when detonation occurs and timing needs to be retarded fuel no longer burns properly due to conditions in the chambers and you begin to get more carbon build up due to lack of heat and lower power as a result. And less scavenging of the exhaust which means moist cool exhaust sitting in your exhaust system longer leaving even more deposits.

As I pointed out earlier I was over the top in my post(except on the fuel cost over time, that was fact, oh and engine replacement costs less labour and incidentals, you got the point though) for the simple fact to prove a point on the effects of risk versus gain. So the guy saves $520 a year going regular, wow, clap, clap, clap...guarantee him he will never damage his engine running regular it's entire life, however long, or short, that may be...the owner manual says premium.

My wife's Alero says regular. 200cc's larger than my engine and 50hp less, hmm.

A Benz is like a good wife: Not overly expensive to maintain, but neglected gets expensive awfully quick!
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