woofwoofz

Hello folks, any one use Ultra94 from Sunoco? It has 10% ethanol in it. Is that okay for the C300 engine? I saw somewhere that it could also save on gas too.

-DW

Glyn M Ruck

Ethanol has a lower density, calorific value etc than gasoline so it will, at 10%, give you marginally worse gas mileage. If you have a flex fuel car it will do no damage.

angeloxnet

i ONLY use Shell 91 V-power ( Has no ethanol)

Krytech

Not sure where you are from but here in the US, I think all C300's are flex fuel and can run up to E85.

My C350 is not however but here in MN all our gas is mandated to have 10% ethanol. They're considering raising it too...

Mark08859

If you're filling up at Sunoco, you should be using the premium, not the Ultra. The premium meets your engine requirements. You're needlessly spending extra $$ for the octane in the Ultra.

RLE

10% ethanol will drop your gas mileage by 10%. We had four years of that stuff in wintertime here in Seattle before air quality met EPA requirements and it was cancelled. And every November, the first tank of it dropped my mileage from 20 to 18mpg.

The companies that use it year round when they don't have to do so because of the tax advantage. To them.

Glyn M Ruck

It will not drop your gas mileage by 10% - that is suggesting that the ethanol has no calorific value at all. It will drop your mileage by a couple of % - maybe 2 or 3%

RLE

Since you are dismissing my hands-on personal experience based on four years of E10 winter use, I would like to hear your source of info. And not just theory, please.

Glyn M Ruck

My source of info is 38 years in the petroleum industry (an American supermajor) & experience of ethanol laced fuels. Endless dynamometer testing of a vast range of fuels & blends around the globe - see my profile.

Winter fuels inherently have lower calorific value due to a modified distillation curve, and contain a greater proportion of light ends to improve starting and driveability. You would get worse gas mileage in winter with no ethanol present - trust this clarifies without being over theoretical

BerBer63

In your opinion, what do you think the gains are for the N/A 6.3 when using 91 vs. 93/94 octane on a DJ. All other variables equivalent....?

Thanks

Glyn M Ruck

The gains would be Zero - Octane rating of a fuel is it's resistance to knock, pinging, pre combustion, detonation - by whatever name you know it. The potential power to be gained from a fuel is determined by it's calorific value or energy, which is mainly governed by it's density.

One caveat - if the knock sensor in the engine is detecting the onset of knock with the lower octane fuel & perpetually retarding the timing then you will suffer power loss & worse gas mileage.

What is the compression ratio of your NA 6.3? This is however, only one consideration in an engine's sensitivity to knock. Other design parameters such as combustion chamber design etc. can effect this.

As an industry man, unless I'm driving a really low tech engine I tend to run on the highest octane fuel available - accepting that some octane giveaway is taking place. This can of course be a total waste of money because if you don't need it you don't need it. If the vehicle is not modified stick to the OEM recommendation for octane. They will have tested the engines octane requirement to ensure longevity as it ages and deposits build up etc. Knock is extremely destructive.

Glyn M Ruck

Another point - Alcohols such as ethanol tend to raise the research octane of a fuel and don't do much for the Motor octane rating. Do you know what is being stated on your pumps? Motor octane or Research octane? I think that all states in the US now require the petroleum companies to state Motor octane. Some parts of the world don't demand this & things become murky in this regard.

SolanNo1

This is from personal experience. I have ALWAYS filled up my cars with Shell V Power (93?) gas.

Last week, I drove to NYC in my 545i and got 25.6 mpg on my way to on Shell. On the return, I had no choice but to stop and fill up with Sunoco Ultra (NJTP only has Sunoco stations and I was not inclined to exit the highway to look for a Shell station). I averaged 23.2 with Sunoco Ultra. I don't believe I drove any differently on my way back and the comparison is essentially apples to apples.

So there.....

ctgilles

I fill up with whatever comes out of the pump lol

Glyn M Ruck

So there what? Have you any idea how many things effect fuel consumption, gradient, speed, inlet air temperature (huge), prevailing wind, fuel density etc ad infinitum, Just to stabalise fuel consumption on a dyno can take weeks - search - I wrote an article on the subject on the 203 forum.

woofwoofz

Glyn, can you point me to your article?

SolanNo1

I apologize if I have rubbed you the wrong way and ticked you off . You may have written an article and I salute you for that.

Just to clarify
- The air temp on the way to NYC was lower than on the way back (thus the density of the fuel was higher to than from)
- Both NYC and WDC are appox the same altitude. I used the same route going and returning so the gradient is a wash
- The average speed going was higher than the average return speed

Anecdotal, yes. But enough for me to believe that, in a real world environment, I got better mileage from Shell than Sunoco. And I don't own Shell stock.

Glyn M Ruck

You have not rubbed me up - I thrive on robust interaction - Please don't worry

You could well be right & got a load of less dense fuel from Sunoco - If you know the way the oil industry works they exchange product all over the place depending on who has a refinery where so you can buy Shell produced fuel from Sunoco and vice versa. The only difference would be the clean up additives added if there are any. Shell, Chevron, Texaco etc. all use cleanup/keep clean additives. I don't know about Sunoco.

All I'm saying is that getting repeatable fuel economy results on road is impossible.

Glyn M Ruck

Hi woof - I can't find it. We have combined so many threads - It covered what we are talking about in Tru's thread after he fitted an AMS pulley. Tru wanted to do some on road fuel consumption testing & I dissuaded him.

paste from Tru Taing's very long thread:

Tru - no base line makes this futile - don't worry. Wind (direction & force), driving style, tyre pressures, lightly binding brakes, inlet air temperature etc. etc. etc. all have huge effects. I ran tests with our AA a number of years ago on a fleet of 10 cars on a perfectly calibrated Schenk eddy current, rolling road Dyno on friction modified engine oil. We were looking for savings in the 2 to 7% range with >90% confidence & finally achieved 7% saving over 10 Kms from a cold start & 2% fully warmed up. We had to lock the servos on the dyno. Weld braces all over the dyno bed to get noise out of our signals. Fix the throttle positions on the cars. Push back pads in the calipers so they did not touch the discs. Control inlet air temperature with a cooling tower on the roof. etc etc etc & confirm in an altitude compensated dyno room. The test took a year running at 6 in the morning, 2 in the afternoon & 10 at night to achieve proper results.

1 to 2 degrees change in inlet air temperature will cause a float in results in excess of the saving you are trying to prove. So take my advice & forget it. It's a minefield. OK I was looking for results that could stand the scrutiny of opposition oil companies.

It's not worth the effort. That's why no one bothers to try & drive the European cycle any longer. OEMs place their cars on computer controlled dynos in controled conditions & let the computer drive the vehicle & monitor all parameters.

BTW - Sasol's Sastech has some of the few altitude compensated dyno facilities in the world. Most F1 engines come here for testing.

Anyone who tries to tell you that a pulley is giving a reliable 2% fuel saving & has not applied this level of rigor to testing is talking BS.
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01-28-2009, 05:08 PM #171
UK-C200
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Join Date: Nov 2007
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Drives: 2004 C200 Sport Coupe, 2006 SLK-350 Quote:
Originally Posted by Glyn M Ruck
Tru - no base line makes this futile - don't worry.
<SNIPPED>
Anyone who tries to tell you that a pulley is giving a reliable 2% fuel saving & has not applied this level of rigor to testing is talking BS.

Glyn - thanks for the excellent description of what it takes to do accurate, repeatable consumption testing. I was involved in a long duration fuel consumption project at university as a lab slave. When I ducked out, they were still not able to get results within 10% of the deviation. Obviously not the same scale, scope, nor quality of equipment that you got to play with, but still about $2m worth of kit.

I'm still curious about the impact of a lightweight pulley. I do the math, and I can't make it add up.

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01-28-2009, 05:31 PM #172
Glyn M Ruck
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Drives: late 03 C240 Elegance, '65 Jaguar S Type wires Hi UKC - good to see you on the forum again - Yeah - and my description is skimming the surface. I got repeatability down to about 0.2% & that was 3 months of work on the equipment. Not allowing cars out on the road on their skimmed dyno tyres etc. which meant changing wheels all the time while conditioning & deconditioning the engines with friction modified & non friction modified oil. Keeping the control vehicle under strict lock & key so no one could touch it - A real SOB but I was determined to do as well as Schenk maintained was possible. We started with a water brake blueprinted by Atlas Aircraft Corp - NO GOOD. Your 10% is no surprise.

Yeah - this pulley - well I'm trying to be fair - nuff said!
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01-28-2009, 07:29 PM #173
Mu9enx
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dang, glyn, your wisdom and expertise are definitely appreciated, even by a young buck like me! thanks

We were talking about effects of aftermarket pulleys - we moved to this thread so as not to pollute Tru's thread - see our pulley discussion

https://mbworld.org/forums/c-class-w...iscussion.html

You might also find my post on crankshaft resonance of interest

woofwoofz

Thanks Glyn!

NJBNZ

i always use regular gas and never had a problem...it's only a lease so no point in wasting the extra money