Octane: 98 versus 95 in a '91 M104 engine

[rayhennig]

Not an M119 engine but similar vintage.

Is this my imagination?

This is European octane ratings.

I use premium fuel; usually Total. Our 2 local towns both have Total garages. One sells E10, E85, Diesel and 98. I usually get the 98 there.

Today, I was in the other town. Diesel and 95 E5 only available there. Filled up with 80 litres.

On the way back, I felt that things seemed smoother. Responses are always good but there was a suggestion of greater smoothness.

Has dementia finally set in? Anyone else experienced any 98/95 differences?

Comments?

Best to all.

RayH

 

[gsxr]

I've never experienced, or heard of, improved running of any kind (smoothness or otherwise) with lower octane fuel.

Strange.

 

[rayhennig]

I've never experienced, or heard of, improved running of any kind (smoothness or otherwise) with lower octane fuel.

Strange.

But you have heard of dementia?

And dilusion?

R

 

[R129 UK]

I've never experienced, or heard of, improved running of any kind (smoothness or otherwise) with lower octane fuel.

Strange.

Am I missing something here?

Isn't E5 (which OP filled up with) a higher octane that E10?

 

[rayhennig]

Am I missing something here?

Isn't E5 (which OP filled up with) a higher octane that E10?

Here in France, E5 is available as 95 and 98. I use one or the other but more often 98 as that's what's served up at my town of choice.

E10 is usually referred to as E10 95? Not 98.

My son once put E10 into my M104 and he said it was fine. But I worry about rubber in the fuel system, particularly the newish Ke-Jetronic fuel distributor installed in 2017.

Does that clarify?

R

 

[R129 UK]

Here in France, E5 is available as 95 and 98. I use one or the other but more often 98 as that's what's served up at my town of choice.

E10 is usually referred to as E10 95? Not 98.

My son once put E10 into my M104 and he said it was fine. But I worry about rubber in the fuel system, particularly the newish Ke-Jetronic fuel distributor installed in 2017.

Does that clarify?

R

I think so, I was just going off the EX number in your OP and not considering the octane rating.

 

[BRABUS124]

Long story short. The M104.980 engine is the high revving 3.0-24 engine with dual head cams and variable timing.
Thise engines uses the KE jetronic with EZL canbus ignition module with nock sensors.
Rhat said the knock sensors are only to avoid knocking. Not for automatic gasoline octane adjustments. Just like the Ealy M119 did.
Theres a knob/plug to be fitted on the EZL module for what octane rating your driving on.
This kniv is factory set for the highest octane possible for this engine and that 95 unleaded octane. Meaning what ever you fill it up with as higher I tanke raton won't be better or more effecuent or better bang. In fact it's the opposite of that as the ignition has to be set to make use for getting more power from it. Othervice it's just harder to ignite hence the benifit of more agresive ignition timing to gain more power without knocking.

Only the AMG 3.4 and 3.6 is set for the use of 98 octane in the software of the EZL or HFM and will be running hot if used with 95 octane. As the knock sensors constantly tries to readjust back to 98 octane ignition setting. Making it taste a bit of knocking micro seconds ever now and then,

So that's about the octane ratings RON ratings.

The E for ethanol is the % of ethanol mixed in that gasoline. And of cause you want as low as possible for the car not a twining to much moister in the tank and fuel system under storage. Always go for the least amount of E

So enyrhing felt or convinced is making the car run more smoth or better is pure placebo effect.

 

[phoenix217]

I might just share an observation I made as I am often in France with my AMG's.

In Germany, of course, I only fill up with 102 octane. But in France (especially in Normandy and Brittany) they usually only have 95 and 98 octane.

My M113K for example runs much more aggressively on the 98 octane - I do not have that in Germany. I get a lot more blubber and generally have a lot more fun. Same with my M113 NA's and M120.

I do not use the Total petrol stations in France unless absolutely necessary. Instead I use the supermarkets - mostly Carrefour.

 

[BRABUS124]

The octane number you AMG is set to use is 98 octane as the higher octane were not around when the car were born. Meaning thus is what it will run most efficient on.
Higher octane number means harder to ignite. Again meaning if you ignition setting is set to use 98 octane the 102 will be less efficient burning as it will need more aggressive ignition to fit the 102 octanes maximum just before making the knocking.
So that's eksactly why you have that eksperince

 

[phoenix217]

The octane number you AMG is set to use is 98 octane as the higher octane were not around when the car were born. Meaning thus is what it will run most efficient on.
Higher octane number means harder to ignite. Again meaning if you ignition setting is set to use 98 octane the 102 will be less efficient burning as it will need more aggressive ignition to fit the 102 octanes maximum just before making the knocking.
So that's eksactly why you have that eksperince

In Germany I drive my cars very hard, so I like the extra reserve before the engine starts knocking.
France is a different way of driving, much more relaxed, almost no full throttle. That adds to the blubber.

 

[BRABUS124]

In Germany I drive my cars very hard, so I like the extra reserve before the engine starts knocking.
France is a different way of driving, much more relaxed, almost no full throttle. That adds to the blubber.

But in fact you don't need Ekstra reserve as the engine knock sensors will catch that and in that given 98 octane setting the cars alreaddy has a margin build in safty for not knocking or being close to it. In fact the engine builds up less carbon dioxid as aresaukt of a better more eficient combustion. We, are, talkibg in the small here but it is a difrence to the better to run on the octane the car is meant to drive on. But each should we do what we want.