1991 300SE: Premium or regular gas?
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1991 300 SE
1991 300SE: Premium or regular gas?
Hi, I have a 1991 300SE and my dad has been filling it up with regular gas for a pretty long time now. The car used to be my grandma's and when she was alive and she always filled it up with premium and would always get into arguments with my dad saying how it has to be filled up with premium rather than regular. My dad, of course, never listened to her and would always reiterate that regular is better and cheaper for the car. Well, now my grandma has passed away over a year ago and now it is officially our car via her will and my dad still continues to fill it up with regular. Now, I recently acquired my license(18 y.o here) and have been learning a lot about cars and Mercedes. My dad is letting my use the Mercedes until I go to college next year and I keep telling him that it should be filled up with premium but he refuses to allow me to do so. He says that the only thing premium does is that it is a little bit cleaner and gives you a little bit more "oomph" on the highway when you are passing cars. I tried to explain to him that while that is the case, it also gives the car better MPG and is faster and more efficient at all times, not just on the highway. He doesn't think so. I am going to show him this page after you guys give some, hopefully good and informed answers on this issue. Thanks!
Junior Member
Joined: Jan 2011
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From: New Orleans, LA
'94 E420 177K- (for sale, parts car) '92 300E 179K (LEMON)
I ran regular for 2 years in my 94 E420... sure, I have tons of issues with the car because it was never garaged, but the engine is still running strong. While super might be more efficient it still costs A LOT more, and the ends will probably not justify the means.
Super Member
Joined: Nov 2001
Posts: 669
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From: North Bay Area, California
2001 E320
Sure, it will run on regular gasoline, but there is a reason Mercedes puts a sticker on the car that says 'premium fuel only'.
Any time I think of using anything but premium gasoline, I think of the old Fram commercials, with the mechanic saying 'you can pay me now or pay me later'.
Since it's your vehicle, it's your choice of what you think is best for you.
Any time I think of using anything but premium gasoline, I think of the old Fram commercials, with the mechanic saying 'you can pay me now or pay me later'.
Since it's your vehicle, it's your choice of what you think is best for you.
Newbie
Joined: Jul 2011
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300se
Premium fuel has no added energy and is no cleaner than regular fuel. The additional octane allows designers to increase compression and heat in the cylinder without triggering pre-ignition.
If your car does not rattle or ping under load with regular you can continue using it without harm.
See here:http://www.scientificamerican.com/ar...tion-premium-g
Best wishes
Dan
If your car does not rattle or ping under load with regular you can continue using it without harm.
See here:http://www.scientificamerican.com/ar...tion-premium-g
Best wishes
Dan
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Joined: Oct 2009
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1989 300 SE
unblended if you can find it.
A car made in 1991 may, or may not be designed for the ethanol-blended gasoline, you will need to do some research to decide.
Personally, in my 1989 300SE I get the best performance with 91 octane clean gasoline, that is, unblended with ethanol. I don't believe my German-made 1989 straight6 was really intended to burn ethanol blends. on long stretches of highway when it is smoothly purring at 80 like it will go all day, it's whispering to me I made the right decision. Yes it is $4.37 a gal, but don't judge until you try unblended Premium (91) for yourself.
Personally, in my 1989 300SE I get the best performance with 91 octane clean gasoline, that is, unblended with ethanol. I don't believe my German-made 1989 straight6 was really intended to burn ethanol blends. on long stretches of highway when it is smoothly purring at 80 like it will go all day, it's whispering to me I made the right decision. Yes it is $4.37 a gal, but don't judge until you try unblended Premium (91) for yourself.
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Newbie
Joined: Jan 2007
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1991 300SE
A car made in 1991 may, or may not be designed for the ethanol-blended gasoline, you will need to do some research to decide.
Personally, in my 1989 300SE I get the best performance with 91 octane clean gasoline, that is, unblended with ethanol. I don't believe my German-made 1989 straight6 was really intended to burn ethanol blends. on long stretches of highway when it is smoothly purring at 80 like it will go all day, it's whispering to me I made the right decision. Yes it is $4.37 a gal, but don't judge until you try unblended Premium (91) for yourself.
Personally, in my 1989 300SE I get the best performance with 91 octane clean gasoline, that is, unblended with ethanol. I don't believe my German-made 1989 straight6 was really intended to burn ethanol blends. on long stretches of highway when it is smoothly purring at 80 like it will go all day, it's whispering to me I made the right decision. Yes it is $4.37 a gal, but don't judge until you try unblended Premium (91) for yourself.
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MB’s of all kinds.
Run the Premium. There is a reason why Mercedes and many other car makes tell you to. A high compression ratio and/or run at a high temperature and regular gas will ignite prematurely causing detonation and eventually the car WILL knock. Not to mention you get the best performance out of the engine as well. Just make sure your dad puts that he runs regular gas in the ad if and when he sells it... I am sure buyers will come a running. 
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300 SEL 1988
My owners manual (260SE, 300SE & SEL) is very clear 
. "A minimum octane rating of 98 RON and 88 MON is necessary." However on the inside back page a sticker has been put over a line of writing to hide it. The sticker says "Fuel - unleaded only, minimum 91 RON/82 MON."
You wouldn't get knocking with regular fuel because the anti-knock mechanisms would come into play. See http://www.torquecars.com/articles/f...ne-ratings.php
. "A minimum octane rating of 98 RON and 88 MON is necessary." However on the inside back page a sticker has been put over a line of writing to hide it. The sticker says "Fuel - unleaded only, minimum 91 RON/82 MON."You wouldn't get knocking with regular fuel because the anti-knock mechanisms would come into play. See http://www.torquecars.com/articles/f...ne-ratings.php
