I've had my 300SD since late last summer and I've put about 12K miles on it. I've changed oil every 3K miles but I've always managed to put off changing the fuel filters. Until this weekend when I finally decided to stop procrastinating and just do it. Popped in a new air filter also.

Well, let me tell ya, it seems like I'm driving a different car. It's really got some get up and go now. I'm having a lot more fun driving the old boy.

The shift points have changed completely. Under hard acceleration it shifts from 2nd to 3rd at around 3800 to 4000 rpm and into 4th when it gets back up around 3600 rpm. Before it always made the shift to 3rd at much lower rpm and then would almost immediately shift to 4th.
So, was it the new fuel filters that did the trick? Or is a clean air filter the reason for my peppy new feel?

Joe

__________________
Joe

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1980 300SD - 495k miles - 'The Ambassador'
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Former Family Members
95 C280
73 280SEL
90 300D
87 300SDL (X2)
86 560SEL
84 300D
80 300SD

Congratulations on your "new" car. That's gotta feel good

__________________
1994 C280 204k miles

When I brought my 300D up from California (in 1997, then let it sit until 2000) all of the filters were clogged. I firstly replaced fuel filters and adjusted the valves as a way of getting it to run better- some improvement. Then I repalced the air filter. BIG improvement!

I had the same experience when changing fuel filters, but not the same when I changed the air filter.

JCD

Changing the air filter lets the engine get more air. That helps the fuel burn better and improves economy and performance.

A clogged fuel filter will make a diesel run sluggish. The accelerator may need to be pushed to the floor to climb hills. It may be stalling since it isn't getting enough fuel to idle. The engine will require high rpms to keep it running. You'll think the fuel tank is empty, and you could get stranded.

So changing the air and fuel filters really did the trick for you. I've experienced it too, and it is like getting a new engine. If you've always changed the filter before it gets dirty, you won't notice this.

How often do you change fuel filters? I just want to get a sense of what other diesel owners do.

I change my fuel filters and air filter every 20k or two years (usually 2 years lately). I also rotate my air filter every oil change 3k mi. The newer type of Bosch fuel primer pump really makes the fuel filter changing cleaner, easier and faster. Never had a problem restarting with new primer, just intermittent misfires for about 15 seconds.

ATLD

Hi Greg,I have been changing mine every 20,000 km,sometimes I notice a difference,but I've only done 4 changes.My owners manual says every 48,000 km but then I'm a bit anal about stuff like that

__________________
Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

I too have noticed quite a difference in performance when changing fuel filters. I wonder which causes a more significant change the pre-filter or the spin on filter?

I'm another anal one and I change my main fuel filter every year while changing the pre-filter about twice a year or so. Both filters are pretty cheap so I don't feel bad doing it more often. I'm even thinking about doing it more often than that. I have a K&N airfilter which I haven't cleaned yet, but I expect to clean it once a year which is about 15-10K miles.

Alex

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

Could it be that the spin on filter could restrict fuel flow to the IP? I've noticed that the Mann filters have 4 holes compared to the Hengst which have 6. Could this compromise fuel flow?

Question, I heard rotating the air filter... What is this supposed to do???

As diesel fuel seems to be more hydroscopic than gasoline, and cleanliness is more critical, I wonder if there would be merit to an additional in-line filter, or would that put too much of an impediment on the rate of fuel flow, and possibly a strain on the Injector Pump? I know that an additional oil filter is considered to be a good thing, due to the fact that diesel combustion produces sootier deposits in the oil, and that a diesel owner can maximize the drain life of that expensive Mobil 1 Delvac Synth that we almost all seem to be using now. (I plan to add an Amsoil filter in line with the regular filter, just for the additional protection, and possible engine longevity.)
Or am I getting really big and round and smelly?

Big and round maybe Greg,but changing them that often,you shouldn't be smelly

__________________
Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

I change it at 5000 miles whether it needs it or not, & it is still smelly.