smiledr996s

Seems slow today so thought I'd ask. 🙄


I have a 2008 gl 320 cdi and I Typically Try to use shell or Exxon diesel . But does it really matter? I read once that the top tier gas stations put more detergents in the diesel but was not sure if true. Some stations have much cheaper diesel but not worth 8$ if inferior fuel

i have a modified 944 turbo that I only run shell premium in. So if I need to go the same with the 320 cdi no problem

alx

there is no rhyme or reason in regards to diesel fuel quality.

you want to refuel at stations that sell a lot of diesel.

and also avoid biodisel because quality there is very very inconsistent.

DennisG01

I agree - high turnover rate is the key. I've found there can be a cetane difference, but so far I've never found there to be enough of a difference to worry about checking on it.

Now, I do typically use an additive such as FPPF Total Power. There are others and I've tried a number of them without noticing any obvious difference. I don't use the additive for whatever MPG improvement is claimed - haven't noticed any, either. But primarily for the injector cleaner, anti-gel qualities and lubricity. Whether I truly "need" it or not can be debated but for the, literally, pennies a gallon it costs I feel better about using it.

Oh... and stop using the term "gas" in relation to diesel. That would be the BIGGEST mistake you could make by putting gasoline in your tank!

BlownV8

Was this a trick question? Do not ever put gas in your 320 regardless of top tier grade. Use diesel instead.

smiledr996s

I'm actually on the go a lot in different towns short of going to a large 18 wheeler gas station is there problems with ones that have lower volume?

I have no idea how often these diesel tanks are emptied

alx

Go to the truck station. By far the best diesel fuel is there. The nozzles are bigger and will not fit your tank, but you can finesse the trigger and fill up without spilling. And anyway most of them have the "small nozzle" pumps too if you look carefully.

smiledr996s

I will keep a check on that they're not usually close to where I am and also usually much more expensive

I will probably have my injectors pool to replace the seals soon is there anyone the test flows or rebuilds and check these out?

a2j

+1

Fourdiesel

There are a few folks who test/rebuild these injectors but 'precautionary' replacement of the seals is NOT recommended and may cause more harm than good.
Your M-B dealer can run an injector 'dispersion' test by plugging the shop computer in to your vehicle and give you a print out. It only takes a few seconds. Send that to your favorite rebuild shop and have them interpret the results. I had that done and the injector service I use told me I had about 85% service life left and to leave well enough alone [I now have 125k miles on ours and I have a concern about decreasing mileage from several years ago]

smiledr996s

I have never really use the larger truck stations but almost always the smaller ones

I have 145,000 miles on my mileage has seem to be better but I was primarily changing the sales after seeing pictures and tails of the Black Death. I would think replacing the seals would be simple. Is there a problem when pulling the injectors as far as reseating or breaking things?

I have pulled the injectors frequently on my 944 which I know is simpler but I've never had an issue

eric_in_sd

Why not?

Unless you're referring to something in the injector system, there's no problem running gas in a diesel engine.

It's silly to do it, but diesels can tolerate many fuels. Gas engines can't tolerate diesel, though.

BlownV8

Try running gas in a modern MB diesel and see what happens. It will cost you.

eric_in_sd

What happens?

DennisG01

There's too much compression in a diesel engine for gasoline. Gasoline is too volatile. It will "explode" inside the chamber well before it's supposed to. You know how "knocking/pinging" in a gasoline engine can be from pre-detonation? Multiply that by a factor of "X" for what will happen in a diesel engine. Even in older diesel engines, it's a bad idea.

Kerosene, heating oil, etc, yes. With the caveat, of course, that modern diesels are much more finicky. But not gasoline.

eric_in_sd

Nah - I poked around a bit and all the info was basically, this should be a problem, but nobody saying they showed it is. http://www.bellperformance.com/blog/...nd-diesel-fuel even says don't put gasoline in diesel, because the flash point is too low - and don't put diesel in gasoline because the octane (= flash point) is too low.

Terrible for the fuel system, though, because the fuel system uses the oiliness of the diesel for lubricating.

Show me something where they demonstrated rod or crank bearing damage from running gas in a diesel engine. Otherwise it's just that it seems like it should be a problem.

P.S. for the petro-nerds out there: "Octane" refers to heavy hydrocarbons included in the gasoline to raise its flash point - meaning you have to get it hotter before it spontaneously ignites. However, ethanol, added here in the U.S. because we like to make corn farmers rich, also raises the octane rating. That's because the ethanol is lower volatility and the mix raises the gasoline's flash point. Ethanol doesn't contain octane molecules, but raises the octane rating.

P.P.S. Adding diesel should raise the octane rating, but diesel contains few octane molecules ... dunno how that would wash out. Probably eff up your emissions system, much like my GL's habit of drinking oil prolly ain't good for my cats.

DennisG01

Ah, but... why are gas engines limited to about 11:1 compression ratios (and most in the 8 to 10 range)? If the engine's compression is raised higher, then you get pre-ignition. Depending on where in the stroke that happens, the piston might start trying to reverse the engine rotation. Depending on the severity of that, obviously determines possible damage. For example, one piston trying to turn the crank one way, while another is trying to rotate it the other way. Something has to give.

Agree on the fuel system/lubricity.

Diesel is typically rated in regards to cetane.

alx

putting diesel in gas engine will require a fuel system flush. maybe. i personally just drain the diesel from tank and crank for a while and it eventually starts and all is good.

gasoline in diesel engine results usually in catastrophic damage as fuel timing is significantly altered resulting in rotating assembly damages. dpf also gets literally cooked and can start a fire.

eric_in_sd

Source? I found nothing solid about internal damage. The most was why it seemed like it ought to be a problem.

What's a dpf?

alx

source is me

dpf is diesel particulate filter.

you get severe pre/post ignition as gasoline when squeezed that much will detonate way way too early. this results in piston hot spots and destroyed piston faces.

not to mention that gasoline is a detergent. any sludge (and there is plenty in the diesel tank) will clog everything as well as destroy fuel injectors and high pressure pump as unleaded gasoline is not a lubricant.

eric_in_sd

Ah. Diesel Particulate Filter.

So it burns out the particulates. I fail to see the problem with that.

eric_in_sd

well that settles it then


Dunno. Looking into it a bit more, looks like diesels are frickin complicated. Note they're all basically direct injection. I'll bet some are able to handle it better than others.

It's definitely not the same as running low octane gas in a high compression motor.


Didn't know about cetane, btw.

alx

problem is dpf is designed to work at specific exhaust temps.

at cruise speeds typical egt of diesel is 500 degrees... 1100 for gasoline...

eric_in_sd

I was being silly, but had no idea how on-point I was. Since then, I learned what DPFs are, and that they are "regenerated" by purposefully raising the exhaust temperature, or heating the filter.

(However, this is a crummy thing to do from a health standpoint, as invisible nano-particles result from the heating: Soot is broken up into invisibly small particles, which are vastly worse for health. They lodge in your lungs.)

Seems to me the big problem with running gas is that it initiates the regeneration, which generally includes burning off the particles, in an uncontrolled fashion. Apparently some Ford diesels had this problem - particulates would accumulate, and then catch fire, and burn a hole through the side of the DPF. Of course, this is only a problem if the DPF is flimsy; catalytic converters run all day long at elevated temps.

I wonder why the DPF doesn't run more like a catalytic converter. The exhaust gases are cool (relatively) but you could get the exhaust temps you need by running the post-cat exhaust gases back around through a heat exchanger. Use the heat generated by burning the soot to preheat the incoming exhaust. Bulky, but it should work.

The more I learn about diesels, the more I think they really suck. Can't beat the efficiency; the lower temperature of the exhaust is exactly where you see it; but for short trips they're awful. My UPS guy starts the truck, clatter clatter clatter drives a block, stops. Repeat. Diesel is great for big ships, but delivery trucks?

BTW that 1100F exhaust - yeah, maybe if you're running full throttle at high rpms. I've seen glowing exhausts on dyno tested engines, but that's about it.