Best brand of diesel for W123?
 

I've had my '79 240D for around a month now. Filled it up for the second time last night.

The first time I filled it up, I went to Shell.

Last night, I filled up at Arco (I'm in the Los Angeles area). I could swear that from the moment I started it after filling it last night, the engine is not running nearly as smoothly. Idle seems rougher, acceleration (which, as everyone knows, is not exactly strong on the 240D in the first place) is weaker, etc.

1. Is this just my imagination, or have others found that fuel from different refineries makes a noticeable difference in how their cars run?

2. If there is a difference, what brands do people find to be better for their W123s?

Ehh, in my W124 300D it all seems about the same, with the exception of Propel Diesel HPR. Just fill up from a station that has good turnover and keep driving.

I tend to avoid discount chains for the very reason you state. By the time you leave the parking lot, you can tell the difference. My car will nail loudly with crappy fuel, and earlier this year I got a surprise fillup of diesel bug. Joy.

I tend to stick to truck stops, Shell, or Valero stations. I avoid grocery stores and Stripes (used to be Town & Country) like the plague. For a penny or two difference per gallon, I'll buy a known brand.

Perhaps more important than brand is turnover. Always fill up somewhere with high tank turnover - when it sits in there for a while, you get water and biological issues.

The Diesel Fuel that your Car was made to run on is no longer made due to emission issues.

You can look on the pump and see if there is a sticker on it that has the Cetane rating.
https://en.wikipedia.org/wiki/Cetane_number

Some Diesel Additives raise the Cetane number.

If you can go someplace where the Big Rig Diesels fuel up and where they still have the skinny more car like pump instead of that fat over one inch nozzle that is designed to fill a 200 gallon fuel tank fast. Not hard to fine out here as people on lots of diesel pickup trucks and so on.

Going some place were the Truckers go is because if a Trucker gets a bad load of Fuel his is on the Radio telling everyone that can hear to stay away from that Station. That means the Station looses a lager chunk of money and encourages them to take steps to insure they have good clean fuel and to fix a problem fast if they have one.

My Wife usually driver the Mercedes and now lives out of town and I don't know where she fills up. However, when she lived in Long Beach I told here to go to the same place I go. That place way back in the 1970's was known for having good clean fuel (I worked in a Fuel Injection Shop and the Truckers told us that). And, they have commercial accounts so I have never had an issue buying there.


The good news is that the majority of bad fuel issues don't cause damage. They are just a PITA to take care of.

This is all very helpful - thank you.

Diesels are persnickety when it comes to fuel quality. You can tell just a few minutes after filling up whether the fill is good or bad.

It may be regional, but I've found that my 190DT runs consistently better on Shell than any other brand. Smoother, and better fuel economy.

My '79 240D used to run best on the Propel diesel HPR. Better idle, noticeably better acceleration, less smoke. I had decent luck with Arco in the past as well, but the cheap gas stations always caused issues for me.

Fuel Issues
 

This is why it's so important to only use the clear plastic primary fuel intake screen ~ at a glance you can tell if you got dirty fuel or if it has fungus in it .

I mostly buy HPR bio diesel because it's bug free but once in a while I get stuck out on the open road and have to fill up at a branded filling station, the Chevron in Jurupa, Ca. sold my crap dino diesel that looked like COFFEE for chrissakes, that was a pisser .

I've never been able to notice any difference. I have used kerosene in it before too and did not notice anything, though it seemed possibly a bit smoother.

Same with me Tom. The only time I get worried is when the pump is filling really really slow; then I know the tank filters are dirty.

I do try to avoid buying at stations which obviously don't sell much diesel. I have wondered why some stations fill so slowly. Clogged filters he?

bio,if you can get it,lights up faster,and less engine wear.

Since in CA, try Propel's Diesel HPR. My 1985 300D runs smoother, cleans the system and greener than an e-car.

ProPel HPR Bio Diesel Fuel
 

I've been using mostly this ever since my Son hipped me to it, indeed it makes the engine run better and doesn't kill your original rubber hoses like veggie Diesel does .

However, I recently discovered there was still some fungus lurking in the IP when I ran the car nearly to empty (20 gallon fillup) and filled with Dino Diesel and Biobor, within 250 miles my filter in the fuel return hose filled up with incredibly fine black silt .

I think the “seat of the pants” fuel quality assessment is for real. I would say that my personal experience has been consistent with what has been described above. Just substitute brand BP for the one I usually try to get and Exxon for the one I try to avoid.
I suspect that it has everything to do with cetane numbers.
I usually run a bio blend of around 10-20% which I feel deceases tail pipe smoke and increases smoothness overall. I did run some jet-a one time and I can say I could definitely feel that in the seat of my pants.