I wasn't aware of this until recently, but gas stations that sell diesel will sell one of a varrying level of cetane. From my understanding, Cetane level is similar to octane level in a way.

The higher the cetane, the faster it burns, but the better teh car runs. The lower the cetane, the more economical driving the car is.

In Europe a lot of the diesel is cetane 50. From my experience all Amoco's sell 47 cetane, the highest i have seen here. Texaco usaully has 40. Exxon usually has 45. The difference in driving is notable.

Anyone have any opinions on what is best for the life of the car to use?

Cheers

Eric
1985 300TDT (280,005 miles as of today!)

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1995 E320 Sportline Wagon "Bernard"
black on black leather

http://i.imgur.com/BdZ7jM3.png

I have never had the opportunity to try Amoco Premier 47 cetane, but I have had some good results with Sunoco, where the pumps had a sign over them saying "Premium Diesel" but the pump itself said just "Diesel".

Our Gulf station that was selling "Dieselect Premium Diesel" closed, moved, and is now selling Shell at a reopened/formerly closed Amoco station. I haven't tried the Shell yet. There is a Texaco station selling premium diesel, but I haven't tried it yet either.

The only station that posts cetane around here is Hess 42. It's been exactly two fillups since I've either used additive or premium diesel, and I have noticed an decrease in performance. Time for another bottle of Redline DFC or Power Service additive.

As to your question about longevity, I've been under some different impressions. From what Redline puts on their label, I thought that higher cetane meant better fuel economy, less "nailing", and improved performance. I never thought there was any downside at all to using a higher cetane fuel. In other words, I've been under the impression that more is better, in all aspects. I've only been following diesels for a bit over three years, so maybe some more experienced persons may have better information, but that's just what I thought.

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic

I think all things being equal in terms of diesel quality, then sure, higher cetane is better. But, I don't think the variance in cetane from diesel to diesel is as great as the variance in quality from diesel to diesel. In other words, the difference between good diesel and bad diesel is much much bigger than the difference between different cetane ratings. I've never tried 47 cetane diesel, but I can't really tell the difference between Mobil 40CE diesel and Hess 42CE diesel.

Go for the pump with the freshest diesel, not the one that has the highest cetane rating. That is unless the pump with the freshest stuff is also the one with the highest rating. That would be awesome.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Octane is resistance to ignition, cetane is ability to ignite. They are really the opposite ends of the spectrum. Cetane will not make one burn faster than the other, just easier to burn. Easier to burn can make it burn more completely and give more power. I have noticed some pretty substantial differences in power between fuels, but it is the BTU content (specific gravity) of the fuel that makes the difference. In the upper midwest we use a blend of #1 and #2 diesel in the winter to help prevent gelling. The BTU content of #1 is quite a bit less than #2 and the blend makes less power. The heavier the fuel (higher S.G.) the higher the BTU content. Hope this helps clear the cetane subject up a bit.

thanks for all the replies. i'll continue to use the 47 Cetane i find at Amoco who has now merged with BP. so anyone who see's teh green flower on the sign- that's Amoco/BP and try their diesel.

ive had the most success in terms with additives with BG 44K. It's AMAZING. i had a knocking in a cylinder and a local mechanic told me i he would need to flush my system and run a fuel cleaner through everything which would cost $75. i called my home mechanic who said "no way, just go buy 44K and see if it still happens"

so i add 44K and the knocking disappeared almost immediately. 44K is a harsher cleaner for everything including injectors and fuel tank. it cleaned my injectors and removed the knocking. i only use 44K every oil change, but in the meantime for prevantative means i use BG 248 which i also like a lot.

my mechanic likes them both better than readlines products..

cheers
eric

__________________
1995 E320 Sportline Wagon "Bernard"
black on black leather

http://i.imgur.com/BdZ7jM3.png

to post the cetane/octane ratings, and my Texaco "Premium Diesel" pump is rated 45 cetane. My 240 does well on a pretty steady diet of this, but I do notice a difference when I fill up at a Baltimore station where the pumps are 50 cetane. I think the big difference for cetane is in winter starting. The car behaves differently on trips where I often fill at truck pumps...sometimes runs smoother, sometimes rougher.

Just wanted to chime in on the benefits of BG44K. This stuff is great, even cleaned my tank so well as to necessitate a filter change. Now the car is running better and faster than it has in years! I heard Pat Goss (Motorweek, Goss's Garage(local)) touting this stuff, even saying he uses it in his E300 Turbodiesel. Who am I to argue?

FWIW, I get 47 cetane in Northern Virginia.

-Reed
'84 300D/T 148,xxx

I was in northern VA last night and fueled up at an Amoco station that was sellling something called Premium Diesel, though I didn't notice this designation until I was finished. It wasn't until I poured enough Power Services Diesel Kleen into my tank to raise the cetane rating by 6 points did I notice the rating of this Premium Diesel to be 47. So, theoretically, I am now running on a 53 cetane rated tank of fuel. Is there such a thing as too high a rating? My occasional rough idle hasn't been helped yet by this (I figured to try some cleaning additives first before fooling with the rack damper), but it does seem smoother when actually moving along. Though this may be my wishful imagination.

Dan

Simply
Fuels with a low cetane rating , reduce power efficency and mileage because they resist ignition untill after the piston head has passed top dead centre. These fuels also create detonation wear in the combustion chamber because they explode violently rather than igniting evenly.

and now for the really technical bit.....

Cetane- colorless liquid hydrocarbon C15 H34 used as a standard in determining diesel fuel ignition performance

Cetane number- measure of the ignition quality of diesel fuel, expressed as the percentage of cetane that must be mixed with liquid methylnapthaline to produce the same ignition performance asthe diesel fuel being rated, as determined by the test method ASTM D613. (American Society for Testing and Materials) A high cetane number indicates shorter ignitionlag and a cleaner burning fuel.

Now you all know!!!

Surprising the amount of 'useless' information I need in the pursuit of my day job

And for those exponants of renewable fuels Biodiesel is a highly oxygenated fuel which gives it a high cetane reading

In Scotland we have choices diesel or diesel. Though in some stations are now getting 'city' diesel which is low in sulpher and better for you to breathe in cities

I wonder,

Does more than "sufficient" cetane improve running or do you just have to reach a certain cetane level for a given engine? In gas engines, once the required octane rating is reached given a certain combustion chamber design and compression rating, more octane is not going to help much.

Related question: Do you have to reset the injection pump timing advance in order to make use of higher cetane?

Sholin

p.s. I don't own a diesel, so these questions may be obvious to someone who does.

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What else, '73 MB 280 SEL (Lt Blue)
Daily driver: '84 190D 2.2 5 spd.

Hi,
The Cetane Rating has a great bearing on how the engine will run/sound
The reason for this, is The higher the cetane rating, The shorter the delay before combustion initiates.
Combustion does not start immediately, the fuel-whatever the Cetane rating, has to warm up.
On injection, there is a pressure rise phase, during which time the fuel mixes with the air, and vapourises, this leads to greater temperature, and a greater pressure rise untill such time as the fuel ignites.( one reason why there is an advance of so many degrees, to diesel injection)--Direct burning of the fuel does not occur unless the engine is under full load, and only on certain types of motor. ( one reason diesels sometimes sound quieter while accelerating, than while idling!)
The shorter this period of time is, The better, to achieve this you need a high Cetane rating fuel, or a higher temperature air in the combustion chamber.-The lower the cetane rating the longer the delay, and the greater the apparent "Diesel Knock/nailing.
Desmondo and I have been discussing Cetane rating and Biodiesel ( which has a Cetane rating of around 55, and you would be suprised how much quieter the motor will run with it! ) over on the Infopop forum recently, as to how it affects the Injection Timing requirements. For the high Cetane of BioD and SVO, it has been found for the interests of NOx emmissions, that a reduction in Injection advance is needed, of around 2-3 degrees, to in part compensate for the reduction in combustion delay, and hence the peak combustion temperatures, the higher the combustion temperature, the more NOx is created. This is one reason why manufacturers of Gasoline vehicles have tended to lower the compression ratios since the introduction of Emmission Regulations.

Alastair, At The Diesel Combustion Theory Div. SWC.

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http://i190.photobucket.com/albums/z...0TDnoplate.jpg

Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....

As someone already mentioned, higher cetane is great, but fresh clean diesel is better. Sure a pump might have a high cetane number, but what if you're that stations only diesel customer for the week. I say follow the trucks. Here in NJ, it's real easy to find fresh diesel simply because of all the truck stops. Being it that this state is relatively narrow and divide down the middle by the turnpike/Rt 95. Truckers are always pulling over to fill up. Where they fill up is where the fresh stuff is. Follow the trucks

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

don't go to a gas station to fill up right after they have filled their big tanks of fuel.

you see, there is a good bit of water inside those tanks which settles and seperates more or less from the fuel. so after it has been sitting it draws good fuel. but after a truck comes in and fills up the station with fuel, it stirs all the fuel around with the water making the fuel less than optimal


cheers
eric

__________________
1995 E320 Sportline Wagon "Bernard"
black on black leather

http://i.imgur.com/BdZ7jM3.png

To all the expertswho suggested BG 44K. Where can this good stuff be found? Thanks for any help locating this item!

This is where I get it -

Ryno Performance Products

I guess BG Products does not distribute directly to consumers. This was the best on-line deal I found.

-Reed
'84 300D/T