Super Unleaded 98ron - wow!

gizze

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Then why quote my post questioning my responses?


I didn't understand your first reply, post 2, but reading it back I now see that that is what you were saying is the same. I'm still not sure what the 'excrexon' is meant to be, but I get the gist of what was being said now.

Never ever noticed a difference excrexon a car designed for 98 where filling with 95 negatively affects power.
This discussion has been had many times and there is NO technical reason your car should be any better in 98 than 95 unless the car is designed for 98.
 

gizze

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The manual for my car says, 'Use premium unleaded petrol with a minimum octane rating of 95 Ron for all petrol engines except the SL600.'


Yeah, that is the minimum.

But as I posted above, for some reason Mercedes UK doesn't specify using 98 on cars that are set up for it. It is very strange.
 

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I didn't understand your first reply, post 2, but reading it back I now see that that is what you were saying is the same. I'm still not sure what the 'excrexon' is meant to be, but I get the gist of what was being said now.


excrexon = EXCEPT ON

Never ever noticed a difference EXCEPT ON [excrexon] a car designed for 98 where filling with 95 negatively affects power.
 

LostKiwi

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excrexon = EXCEPT ON

Never ever noticed a difference EXCEPT ON [excrexon] a car designed for 98 where filling with 95 negatively affects power.
Yep exactly. Autocorrect on here occasionally screws up badly.
 
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Blimey gents, just on page 2 of the replies haha! Many comments thanks, a good discussion to be had I reckon with lots of opinion and thats what its all about! It is definitely smother as I think John L noted esp. at tickover, possibly thats all? There was pinking frequently if using say Morrissons own 95, no such pinking with super. I will read the next few pages with great interest!!
 

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I hope you've got a good excuse for coming back to the party so late!! :D
 

C350Carl

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So as LostKiwi says above more power is obtained using a higher Octane / Cetane fuel but with diesel no advance or retard of a spark?

BUT if a cleaner burn happens then the bang gives more power ....even if it can`t be measured.....some of us have are more into car`s and therefore have a more sensitive bum!

Adding 2T gives a better burn because of the higher cetane rating it add`s to the diesel......none of you can argue unless you try it?

Speaking as someone who has spent considerable sums of money tuning cars.

Having tried 2T in my C350 CDI for circa 4K miles as well as 2T and VPower Diseasel for circa 3k miles I can categorically say there was NO difference in power or MPG that couldn’t be put down to traffic, road conditions, time of day, ambient air temp, weight in the car, time since last service etc etc

In other words the difference is negligible if there is any.

VPower and other premium diseasel doesn’t give you more power. It may restore and then maintain lost power by cleaning a dirty engine. However once the engine is clean, it’s clean and can’t get any cleaner.

There is nothing other than anecdotal or placebo ‘evidence’ that says 2T does anything in a modern Diesel engine.

Petrol on the other hand does make a difference, assuming your ECU is tuned to take the difference into account.

My Octavia vRS was tuned to use VPower (which in Germany where I was living is 100RON) and gave circa 10bhp and 20lbft more than standard 95. As measured on a dyno. I could also feel the difference in the ‘butt dyno’

I even had a fancy control unit that I could plug into the OBD to switch the map if I happened to need to fill with 95RON fuel. I once forgot and I could feel the car pull back over 4k rpm.

But the key factor is the car was tuned to use the higher octane.

In a standard car (petrol or diseasel) it probably makes sense in terms of mechanical sympathy and preventative maintenance to fill with premium fuels say once every 5 fill ups. It’s something I do.

Looking at this screenshot it will show you that Tesco Diseasel would seem to be the best.

However look just how close VPower and Standard Shell are in terms of MPG (the app won’t show power). The standard at nearly double the distance is only 1mpg ‘worse off’ and shows it’s certainly not worth paying the price for premium diseasel. The extra £8-10 it costs per tank only gets me around 17miles (80ltr tank). I could get around 70-80 miles more by adding £8-10 of standard fuel.

636876a675f97df65b757836f354a656.png
 

gizze

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There is nothing other than anecdotal or placebo ‘evidence’ that says 2T does anything in a modern Diesel engine.

Petrol on the other hand does make a difference, assuming your ECU is tuned to take the difference into account.

In a standard car (petrol or diseasel) it probably makes sense in terms of mechanical sympathy and preventative maintenance to fill with premium fuels say once every 5 fill ups. It’s something I do.




It is worth looking for the thread where the guy runs 2 stroke oil in one of his Freelanders for 100k miles, and then the same fuel in the other Freelander, the difference between how clean the internals were on the car with 2 stroke was stunning.


What is a standard car though?

I think this is the problem with Mercs here, many don't realise they have a car that has a map for 98ron.

If you have a car that has a knock sensor and set up for 98, then there is absolutely no reason at all to use 95.
 

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If you have a car that has a knock sensor and set up for 98, then there is absolutely no reason at all to use 95.
Cost?

Even on my Smart Roadster which is mapped (high state of tune to get 141bhp/litre!) and requires 98 I will run it on 95 if I'm doing a long motorway run where I'm not going to need the power. Can't see the point in paying 10% more to sit on cruise the same speed even if it does do 1-2 mpg less (still ahead on overall cost).
As with Carl's findings the Smart runs best on Tesco Momentum and worst on BP (97) or Shell (98) RON fuels.
 

C350Carl

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It is worth looking for the thread where the guy runs 2 stroke oil in one of his Freelanders for 100k miles, and then the same fuel in the other Freelander, the difference between how clean the internals were on the car with 2 stroke was stunning.


What is a standard car though?

I think this is the problem with Mercs here, many don't realise they have a car that has a map for 98ron.

If you have a car that has a knock sensor and set up for 98, then there is absolutely no reason at all to use 95.

I did say on a modern engine. Can’t comment for older engines. But modern ones (once common rail tech became prevalent so 10yrs or younger) there is no point.
 

gizze

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I did say on a modern engine. Can’t comment for older engines. But modern ones (once common rail tech became prevalent so 10yrs or younger) there is no point.

But many of the new turbo petrols from BMW and Mercedes have maps for 98ron. Just the UK often doesn't mention it.
 

gizze

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Cost?

Even on my Smart Roadster which is mapped (high state of tune to get 141bhp/litre!) and requires 98 I will run it on 95 if I'm doing a long motorway run where I'm not going to need the power. Can't see the point in paying 10% more to sit on cruise the same speed even if it does do 1-2 mpg less (still ahead on overall cost).
As with Carl's findings the Smart runs best on Tesco Momentum and worst on BP (97) or Shell (98) RON fuels.

Ah, but if you have a knock sensor you will *often get more back in MPG than the extra cost of the fuel.

*I say often as it used to cost about 8-10p more, so 6-7% increase, and you would often see 10% better mpg no problem. Shell V Max has often been 20% more at the pump recently, which then means you are paying more.
 

C350Carl

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But many of the new turbo petrols from BMW and Mercedes have maps for 98ron. Just the UK often doesn't mention it.

If I recall correctly they do mention in the owners manuals that lower rated fuel may result in reduced performance.

My mates latest vRS stipulated 98RON in his filler cap cover. But mine only ever said 95.

I’ve yet to see a diesel car stipulate anything other than ‘diesel’ in the filler cap.

Even the likes of a 3/535D and 750D only say diesel.
 

LostKiwi

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Ah, but if you have a knock sensor you will *often get more back in MPG than the extra cost of the fuel.

*I say often as it used to cost about 8-10p more, so 6-7% increase, and you would often see 10% better mpg no problem. Shell V Max has often been 20% more at the pump recently, which then means you are paying more.

The Smart when cruising on motorways (as when we go to France) drops 1-2mpg maximum (from 50+ down to 48+). Serioualy not worth using 98 for those long hauls down the French motorways.

Knock detection only really comes into play at wide throttle openings when boost and cylinder temperatures are high. Fairly rare to have knock detection come into play at cruising speeds on fairly light throttle (at 80mph the Roadster only runs 0.5 bar max whereas WOT is 1.5 bar).
 

Botus

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per litre super unleaded is crazy money, I have not seen an uplift in reduced fuel consumption at all, and unless on it (as LostKiwi says) the only change is an empty wallet

in fact on my bike designed to use 98 can't really say I noticed any change in performance, only a rather nasty coarse vibration in the bars is about 200% more on the silly money stuff
 

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Ah, but if you have a knock sensor you will *often get more back in MPG than the extra cost of the fuel.

The big problem would be on and engine without a knock sensor though as it will cause damage if unsuitable fuel is used.

A lot of engines run a twin spark per cylinder, how do they prevent knock?
 

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Gizze, I wonder if you can tell me whether my 14yr old SL500 (R230) is set up for 98 Ron? I'd like to know what Mercedes Germany advise there, but withold from us Brits. I'd like to run my car on the prescribed fuel.

Thanks
 

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The big problem would be on and engine without a knock sensor though as it will cause damage if unsuitable fuel is used.

A lot of engines run a twin spark per cylinder, how do they prevent knock?
Retarding the ignition. The number of plugs has no bearing on the way the timing is controlled.
 


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