What grade of Unleaded fuel do you use?

[GrahamC230K]

I thought there had been a post on this before, but I could not find it.

All this talk of running diesels on Vegetable oil, and a few friends whose performance cars are designed to run on Super Unleaded, have prompted this.

As I understand it:

Regular Unleaded = 95 RON
Super Unleaded   = 97 RON
Shell Optimax      = 98 RON


My manual for the C230K says to run on unleaded fuel better than 94 RON, hence I just use regular unleaded.

I just wondered what you guys use, and what your experiences are?

Can anyone vouch for a performance increase from Super Unleaded or Optimax from a car which does not require it?

 

[Maff]

Day to day I use regular unleaded. Sometimes I use Shell Optimax if i'm in the mood, but not that often.

I've found the Optimax to give better fuel consumption on long distances, and a smoother engine, but thats about it.

 

[fuzzer]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (GrahamC230K @ Oct. 21 2002,14:44)</td></tr><tr><td id="QUOTE">Super Unleaded   = 97 RON</td></tr></table><span id='postcolor'>
Super unleaded is supposed to be 98 RON <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/slayer.gif" border="0" valign="absmiddle" alt=''>

 

[GrahamC230K]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">=fuzzer,Oct. 21 2002,15:27
Super unleaded is supposed to be 98 RON <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/slayer.gif" border="0" valign="absmiddle" alt=''></td></tr></table><span id='postcolor'>


True until 1999 when it was reduced to 97 RON.

 

[fuzzer]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (GrahamC230K @ Oct. 21 2002,15:44)</td></tr><tr><td id="QUOTE">True until 1999 when it was reduced to 97 RON.</td></tr></table><span id='postcolor'>
Ohh , sneaky buggers. &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/omg.gif" border="0" valign="absmiddle" alt='mg:'>

 

[Guy]

I use Optimax, because I am daft enough to think it makes a difference.

The tests I've seen tend to back that up, and one or two people whose opinions I respect say it does what is claimed for it.

More money than sense?

Absolutely.  <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/hehe.gif" border="0" valign="absmiddle" alt=':hehe:'>

 

[Mark300SL]

I've got a selector under the bonnet of ny 300 - and its set to Super - but runs on std unleaded  <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'>
I had it on the rollers to listen for any detonation - and it was fine! - so if you ever have 15-20 mins dyno time left - check it out.

My Rover cabriolet had had nothing but Optimax since the day it was built - and there is so much advance that std unleaded would probably blow it - again

Mark

 

[GrahamC230K]

So if I have the extra change in my pocket, Super or Optimax is worth a tank full?

I know my car runs fine on 95 RON unleaded, but would it actually go noticably better on Super?

I know, of course I need to try it, but I think any difference will be aided by my imagination. I need to look the other way at the petrol pump and see what I get. Hopefully not LRP or Diesel &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=''>

 

[fuzzer]

Im sure that mercedes recomend the use of 98 RON with any car with a supercharger on it .

Ive read in a Mercedes manual that 95 RON is ok for normal running about , but should not be used &nbsp;full throttle in the case of full throttle , 98 RON should be used.

 

[jimmy]

I use regular unleaded for every day use but have tried both super unleaded and Optimax.

I do notice an improvement with Optimax, feels smoother and a bit more lively and slightly more MPG. I personally don't think it is worth paying the extra all the time for daily town driving, but today I filled up with Optimax as I had to go on a long trip and thought it would be better.

Incidently, I have a friend who runs an oldish Transit on used chip shop oil. <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/dontgetit.gif" border="0" valign="absmiddle" alt=':dontgetit:'>  He has been doing it for about three years and collects the oil in drums and mixes a little ethanol or methanol with it.

He says it starts and runs OK, but you don't want to be following him unless you like the smell of fish and chips! <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>  <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>

He must have saved a fortune over the past few years.

 

[GrahamC230K]

OK, I just checked my manual again, just to be sure.

95 RON minimum is the recommended grade. In circumstances where this is not available an absolute minimum of 91ROn is acceptable, however full throttle driving is not recommended and high fuel consumption is to be expected.


I am torn. Optimax claims to be cleaner for the engine as well as increasing power.

I do not really understand how this is so (technically) and their website does not go into great detail. Their claims seem to good to be true.

Who would support this argument:

&quot;Putting a fuel of higher octane than the recommended is like pouring money into the exchequer. Your engine was designed to run on normal unleaded, using super doesn't give you anymore power in your modern engine.

Its produced so that cars with high compression engines would run on unleaded without the need to adjust the timing. Modern injection engines have a knock detector which adjusts the timing if it detects a 'pinking' condition, a result of using lower octane fuel with a correct timimg setting. The use of higher octane fuel is ignored by such systems, the unit believing that because there is no knock the octane number must be correct.&quot;

Can anyone with some expertise comment on the merit of this quote?

If my engine can make use of the higher RON fuel (by advancing the timing?), I would use it. If it can't, then I 'll save my money.

 

[V12]

Always run on regular, never had any problems with any type of merc, from C180's up to S600's...

I do run premium in cars younger than 2 years old though... <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''>

 

[Sp!ke]

My manual suggests I use Super, especially on motorway runs.

I'm rather lucky in the fact that my company pays all my fuel still &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''> &nbsp;(now thats a perk huh&#33<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''> so I always *try* to use super unleaded or Optimax but I find now that many petrol stations dont stock it anymore.

Anyone else notice this, or is it only me?

 

[Koolvin]

optimax promotion:

 

[Mark300SL]

Graham

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">95 RON minimum is the recommended grade. In circumstances where this is not available an absolute minimum of 91ROn is acceptable, however full throttle driving is not recommended and high fuel consumption is to be expected. </td></tr></table><span id='postcolor'>

This is interesting as it appears the &quot;high fuel consumption&quot; would be because of retarded ignition timing

I havnt been around MB's long enough to know for sure on this one - but here is how it works on Hondas

The ecu uses a knock sensor to try and detect any  detonation (pinking) while its still in its earliest stages.  So in the UK the ecu starts at 100 octane settings for advance and begins to monitor.
If it detects knock it will retard the timing until the knock is gone and log the settings in its &quot;adaptive&quot; settings as the &quot;norm&quot; for this driver/conditions

Now lets say I get in and try to drive agressively - the ecu responds by slightly advancing the timing until it can just see knock again -then retards a fraction.

This adaptive learning process happens all the time the ecu detects a change in driving style

So if MB use a similar system - the electronics will detect what fuel you have and adjust the timing accordingly - therefore you can use optimax to all its potential!

HTH

Mark

 

[Guy]

I couldn't have written that.

But having read it, I agree &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/huh2.gif" border="0" valign="absmiddle" alt=':huh:'> &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>

 

[GrahamC230K]

Thanks mark/Guy. On that basis, I will upgrade my fuel.

What is the point of modding, if you don't even run the car on the top juice??

I have just put £40 of regular stuff in, but next week I'll try some Shell Optimax (if I can find a Shell station! LOL).

If anyone can confirm where a modern Merc ECU starts is calibration - 100 RON, 98 etc I think we would all be interested.

Honda may be different, as being a Japanese car, it is probably designed for the 100RON fuel which is the norm in Japan. I guess what we really need to know is - is the fuel available in Germany better than ours?

This Link and others, support the fact that in Germany regular unleaded is 91RON and there Super diffres between 95-98 RON.

This would explain the absolute minimum rating in the handbook and also why some people have see original MB documentation saying to run on Super, I believe.

 

[Shude]

When in DE I ran my car on 98 RON petrol, on the grounds that it was loads cheaper than the supermarket petrol I usually get in the UK and I was getting ready for some high speed driving. &nbsp;It was awesome, I used less fuel (at 120mph+ sustained you tend to use a lot anyway), my car felt a little more responsive, and Steve (MBenzNL) said he could smell all the cr*p being shifted from my engine when I overtook him at 140mph+ on the autobahn <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''> &nbsp;The engine sounded a little sweeter too.

 

[Billy]

I run on Optimax because I collect the Top Trump Cards.

I can also remember playing with them when I was at school. <img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/blush.gif" border="0" valign="absmiddle" alt=':blush:'> &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/banana.gif" border="0" valign="absmiddle" alt=':bannana:'> &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/banana.gif" border="0" valign="absmiddle" alt=':bannana:'> &nbsp;<img src="http://www.mbclub.co.uk/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>

 

[GrahamC230K]

I got my first tank of Optimax last night, so lets see.