akbro93704

hey!! my grandpa seems to think that you can use any gasoline fuel as long as its unleaded in his car(which every fuel now a days is)...and he's been using 87 octane in his '04 E320 since it was brand new...is that ruining his engine??thanks!

EclassOzz

sorry to say this..but yer grandpa is a cheap ***..im pretty sure its not good for the motor...why's he worried about saving 2-3 dollars? tell him get a echo or something..cheap ***..hah

northbenz

I don't think you are going to do anything to hurt the motor. It is all the related smog gear and fuel injection parts that could be costly to repair. That stuff is so sensitive that if you leave your engine running when you refuel you are likely to set off the check engine light.

vtec26

the main thing octane affects timing. it does so by the car's computer sensing "knock" (a bad thing). running lower octane will increase the chances of knocking, especially in high compression cars. i'm not sure what the compression of the e320 is though. but to make a long asnwer short, the computer won't let anything bad happen to the motor or parts. it will adjust timing to make sure nothing bad happens. the result of this can be less power. hope that helps a bit. if you really want to know everything about octance, i can post up some links for you.

jyg e500 maybe

as timing is retarded and you get poorer gas milege on the cheaper fuel. stay with 91

Silver_Lana

JYG E500 is absolutely correct.

When you use a lower grade fuel than the car is desiged to, the ECU retards timing to reduce or eliminate the possibility of engine knock which can cause damage. What does that translate to in the real world?
a) Loss in Power.
b) Loss in fuel economy.

Unless the driver of the car is a relatively slow driver, they will not notice any increase in fuel economy and might even see worse economy.

What I do in my SLK is mix the 89 grade and the 93 grade fuels to average things out towards 91.
When I reach a half tank on 93, I top off with 89 from the same brand. On reaching half again I top off with 93.

This works for me and I see an average mileage of about 25-27mpg with agressive driving on an SLK320.

Cheers!

Disclaimer: Your mileage may vary from mine.

NATS64

This is what I do also. Some Shell stations in this area have 91 octane, but they are sometimes hard to find.

GDawgC220

the computer retards timing so that your engine does not detonate. Short run, not really a problem. Long run, maybe some carbon build up.

every owner who has tried other than premium has experienced same MPG or a few miles lost. It really depends, it's not the same across the board. you may also lose a few HP, which you would not feel anyhow.

Stricks

All of the above are correct. Loss of power should only be noticed (maybe) when doing some hard acceleration or climbing a steep hill. This same question pops up every time gas prices spike. Years ago it was answered in the "Technical Section" of The Star Magazine (MBUSA Club Magazine) and the answer then was "no problem" (short description of the long technical analysis that was written of going from "super" to "mid range" fuel. The next issue had an "official" retraction from MBUSA that was somewhat blustery and lame. Understand that was before the AMG cars were running around here. Frankly I would not use a lower garde in those cars, but for the "run of the mill" 4, 6 and 8 cylinder cars it should not be a problem. The modern computer systems should take care of any lower grade issues and stop any potential "pinging" in the engine. As to carbon buildup, most all fuels these days have enough detergent in them to negate that concern.

GDawgC220

yes, also another statement to back up the use of the range of fuels offered was that in a study done, when MB was interviewed, they said "if you do not use premium, then you may not achieve the power output specified for your specific vehicle." If they are strictly to run on premium, then I would think they would state it for everyone to read and show how strongly they stand by it.

What I would do or tell your grandfather, mix it up every few tanks. Give it 91/93 every other tank.

kort677

In my Volvo I've always used regular in it, with no obvious bad results, the car has almost 30k miles on it, the mfg. Like MB the mfg. says to use only premium. so much for their advice

Barry45RPM

Where I live (USA) the difference in price between 87 Regular octane & Premium gas that is called for by MB, is NOT 15 cents a gallon...However even using this vast a price difference, if you figure .15 X 18 Gal Full tank fill-up X 52 Weeks = $140.00/year... Not that much when you consider loss of power & milage, which you will get since the computer WILL retard the timing to avoid pre-detonation, or knocking, which will hurt an engine.

Juggle those figures if you fill up more than once a week or the price difference is greater or lesser than fifteen cents.

Of course, if you NEED to fill up & premium is NOT available a couple of gallons of anything, followed by a fill-up of premium as soon as possibe, will have to do. If these "shortages" persist, you'll have no alternative...

Also bear in mind, the Federal Govt will be stepping in to override State laws which require a certain gas formulation be offered for sale in THAT state only. There will be federal specs on the gas formulations, so that plentyfull gas in a neighboring State can be shipped to a State low on supplies, which under current State llaws CAN NOT be done now. This will happen within weeks.

TechSuperstar

Using the better gas does seem to have more power. As far as mileage, I'm not too sure. I have heard people say they get better mileage with the better gas and I thought I was too. Recently I decided to use the onboard computer (C230k) to check the fuel mileage. I filled up with 91oct, reset the trip counter, when the tank was almost empty I check the readout and it was 23.2 mpg. So then I filled up with 89oct and reset the trip. When the tank was close to empty I checked it and it read 23.2 mpg. I actually filled up a couple times now and each time it reads 23.2 near the end of the tank. Just a guess but whatever math formula Merc is using to compute this has some small error in it.

Emirati

On Owner's Manual minimum octane number 95 RON / 85 MON

we have 98 and 95

I use 95 is that bad?

tntmcj

when asked this question by customers i usually tell them what the techs here told me long term use of lower octane fuels is evident in benzes when the motors had been taken apart, heavy carbon build up in cylinders and heads, now that the newer cars have knock sensors and electronically controlled engines not seeing it as much but do notice higher concentration of carbon build up, long term 50-60-70k, do not have time to do the math on savings but probably penny wise and dollar foolish.

GDawgC220

if your worried about detonation and knocking, you can have the dealer set the ECU to take a lower octane rating.

But I think the best way would be to mix up the tanks...one week put in 91/93 and the next 89. If your going to put in a lower grade, put 89 minimum.

But his benz, his choice.