Fuel 98/95 RON?

[mkoesel]

Originally Posted by 13eastie

It's possible that manufacturers simply do not recommend higher ratings in the States because (un)availability might put customers off.

Right, yes, I was referring to US spec cars.

I think they may also adjust the car based on gasoline for the region. In fact he ECU will handle that I believe. IOW, US specs cars may have timing retarded slightly compared to UK. Don't know that for sure though - just a guess.

[13eastie]

Originally Posted by southlight

Problem here in Germany is that RON98 is no more available at the big stations, either 95 or Ultimate/VPower (means RON100). That bothers me, especially since the current premium for Ultimate is 13 cent (makes 1.50 € per liter).

Best regards, south

BP offers a RON 102 petrol at nine locations in the U.K.
Don't know the price per litre though.
http://www.bp.com/genericsection.do?...tentId=7017179

[lucid]

Above a certain octane rating, higher octane fuel would no longer yield a torque output benefit as the spark can only be advanced so much, at which point the only way to benefit from the higher octane fuel would be to increase the compression ratio by redesigning the geometry. So, it'd be interested in seeing data on a 102 RON dyno run.

[lucid]

Originally Posted by mkoesel

Right, yes, I was referring to US spec cars.

I think they may also adjust the car based on gasoline for the region. In fact he ECU will handle that I believe. IOW, US specs cars may have timing retarded slightly compared to UK. Don't know that for sure though - just a guess.

This must be true. It probably does not require calibration and is something that the ECU does automatically based on knock sensor input. Or, maybe the US ECUs are progmmed for it at the factory.

[OzStriker]

Thanks for posting that graph eastie, thats awesome!

[13eastie]

A lot of interesting stuff here.



Salient points:

1. B.P. RON 102 costs (wait for it) £2.50 per litre!
2. B.P. RON 102 does not appear to offer a significant performance benefit over Tesco RON 99 on the E46 M3 CSL
3. Tesco RON 99 appears to be the best option in terms of absolute performance and value for money

[lucid]

Originally Posted by 13eastie

A lot of interesting stuff here.

Salient points:

1. B.P. RON 102 costs (wait for it) £2.50 per litre!
2. B.P. RON 102 does not appear to offer a significant performance benefit over Tesco RON 99 on the E46 M3 CSL
3. Tesco RON 99 appears to be the best option in terms of absolute performance and value for money

Thanks for the 102 RON data. As I mentioned, above a certain octane rating, higher octane fuel no longer yields torque output benefit as the spark can only be advanced so much. It seems like 102 RON might be close to where that's happening for the CSL.

[JPH]

Does anyone know the maintenance implications of using a lower grade fuel? In other words, if you ust a lower grade fuel, what long term damage is expected...if any?

[GregW / Oregon]

Originally Posted by JPH

Does anyone know the maintenance implications of using a lower grade fuel? In other words, if you ust a lower grade fuel, what long term damage is expected...if any?

Not specifically, but why even consider doing it? The US manual calls for AKI 91 minimum (93 preferred). Why would you use, say 89, to save maybe 3% on fuel? Likely the engine will be less efficient, negating any cost savings on the fuel purchase.

[rvacha]

I think all modern engines are OK with low octane since they have rather sophisticated knock sensors. There are vast expanses of North America where the only thing available is 85 octane, and I've run a lot of that stuff in all of my BMWs. The only time I've had an issue with 85 octane was in the M5 in Death Valley with temps running 108-115F. Here the SES light came on and stayed on the whole time I was in the Valley. Fuel economy really doesn't suffer that much, but power does. This possibly explains why 85 octane is so prevalent in the Rockies and Colorado plateau. Where I have a choice, however, I always use 91 or higher

The M5 was panting here at 112F on 85 octane:

[JPH]

Originally Posted by lucid

Thanks for the 102 RON data. As I mentioned, above a certain octane rating, higher octane fuel no longer yields torque output benefit as the spark can only be advanced so much. It seems like 102 RON might be close to where that's happening for the CSL.

The efficiency point is a good one (direct cost savings negated by less engine efficiency). I mix it up and run 87 oct. in my 330Ci from time to time and i can't say as I have ever noticed any incredibly significant differences in performance. But, that is a 330Ci...not an M3.

Truth be told, I won't run anything less than 91 oct in the new M3...until about year 2 when I catch myself feeling like a cheap bastard and filler-up with 87...just to see what happens

[kbk_75]

Originally Posted by mkoesel

...At the same time, I doubt BMW will recommend anything over 91 for this car. Can anyone point to a non-exotic car that actually recommends above 91? I am not saying there is not one, but I will be interested in hearing which car that is.

That's because there are very few road cars (including exotics) that run a 12:1 compression ratio like the current M3 does. I don't know what Lamborghini recommends for the just-announced Gallardo LP560-4, but that car has a 12.5:1 compression ratio, so it would be interesting to know, for comparison's sake.

[mkoesel]

Originally Posted by kbk_75

That's because there are very few road cars (including exotics) that run a 12:1 compression ratio like the current M3 does. I don't know what Lamborghini recommends for the just-announced Gallardo LP560-4, but that car has a 12.5:1 compression ratio, so it would be interesting to know, for comparison's sake.

Certainly compression ratio is the limiting factor. I brought up exotics precisely because those are the examples where high compression is likely. I agree that high compression ratios are rare overall, but if we consider only exotics then they are actually quite common. The point here is that most manufacturers (even those of exotics) don't design road going engines such that they require higher than 91 octane (US). Being that this is the case, it followed that the M3 will unlikely be the one to buck that trend. And as it turns out, that was very sound logic. Though as pointed out above, while 91 or higher is indeed recommended, 93 is preferred.

Furthermore, even if it turns out Lamborghini (or whichever supercar make) does recommend 93 or whatever for some car, that does not change the fact that a 60k car that is meant to function well as a daily driver will only the very far-fetched and most highly unlikely of cases require higher than 91 octane gasoline.

Having said all that, I don't know what the LP-560-4 requires.

[JEllis]

Originally Posted by mkoesel

Ok true. My point to JEllis, though, was that 98 RON in UK does not translate to "98 Octane" in California.

Okay, 93 Octane is hard to find in Cali...most places have 91...

Oh well

Jason

[swiss_cornholio]

Originally Posted by southlight

Problem here in Germany is that RON98 is no more available at the big stations, either 95 or Ultimate/VPower (means RON100). That bothers me, especially since the current premium for Ultimate is 13 cent (makes 1.50 € per liter).

Best regards, south

In Switzerland you get 95/98 everywhere except at some Shell stations where you get 95/100.

Compared to 95, 98 is +4cts and 100 is +13cts. So 98 is really best value for money.

[southlight]

Originally Posted by swiss_cornholio

In Switzerland you get 95/98 everywhere except at some Shell stations where you get 95/100.

Compared to 95, 98 is +4cts and 100 is +13cts. So 98 is really best value for money.

I should think about moving to Switzerland. What does 98 cost per liter?


Best regards, south

[par4bmw]

Originally Posted by JPH

The efficiency point is a good one (direct cost savings negated by less engine efficiency). I mix it up and run 87 oct. in my 330Ci from time to time and i can't say as I have ever noticed any incredibly significant differences in performance. But, that is a 330Ci...not an M3.

Truth be told, I won't run anything less than 91 oct in the new M3...until about year 2 when I catch myself feeling like a cheap bastard and filler-up with 87...just to see what happens

This logic confuses me. Why would you pay a +$15K remium to get the M3 over the 335 and be worried about 3% higher fuel cost to keep the performance at its peak? At 18 MPG and 10K per year and $.10 difference, the cost is only $4.62 per month.

[ersin]

Just for reference, I always put 93 octane in my E46 M3. The one time my wife took the car she filled it up with regular (87?). I did not notice a difference with regular fuel. Then again, I didn't drive it very hard on that tank either.

[Yonkers]

Consumer Reports did a study on this and found no neglible difference between the two. They said mainly it's for peace of mind.

[kbk_75]

The best fuel I can get in Bombay is 97 RON and I use it exclusively. It costs me 10 INR more per litre (that's around 20% more than 91 RON), but there's no way I'd want my M3 losing power for the sake of cheaper gas!

[lucid]

Originally Posted by Yonkers

Consumer Reports did a study on this and found no neglible difference between the two. They said mainly it's for peace of mind.

Did you not see the data in post #28? What exactly did consumer reports test?

[ersin]

Originally Posted by Yonkers

Consumer Reports did a study on this and found no neglible difference between the two. They said mainly it's for peace of mind.

If they are talking about lesser cars this is true. However, the M3 senses knock through the spark plug wires and adjusts the spark timing to get the best performance from the engine. If you have better gas you get better performance. The E46 M3 did this too, but it had two microphones to sense knock vs. monitoring the electricity in the E9x M3s.

I don't know how many other cars do this, I would guess the majority of cars in the same price range as the M3. For these cars premium gas does make a difference in performance. What is not clear is will lower than premium gas be harder on the engine in terms of longevity, reliability and maintenance. Backing off on timing does protect the engine from bad gas, but how much?