? Fuel filter/fuel mielage? 2000 Beetle TDI

I read somewhere on here that a bad fuel filter can cause poor fuel mileage. Can somebody please explain how?
I'm currently getting 43.6 MPG on the interstate. It has gotten 58.6 MPG.
I've looked it over w/VagCom and can not see an issue. It has all new maintenance items except for the fuel filter. It has a new stat and is doing 92°C./197.6°F. The EGR is set to minimum. PVC is blocked off and is running a draft tube. The snow screen has been removed.

Thanks fwd for all of the help.

News flash! I found the IP timing off. The advance solenoid was running 29.6-30% and corrected it to 2.8 %.

Just replace the fuel filter, it should be replaced every 20,000 miles and the thing is only like $25 tops. It's not much harder than the oil filter, you just have to clamp the lines so you don't leak fuel or get air in them, and don't forget to fill up the filter as much as possible with diesel or power service/similar.

While you're at it you can run a can of LiquiMoly DieselPurge (you could either add it to the tank, fill the fuel filter with it, or run it through the lines like this).

TDIs like clean filtered fuel these are not trucks.

10k = Air, cabin & oil & oil filter.
20k = Fuel filter.

Use ONLY quality parts and oil. Your NB will love you for it.

TDIs like clean filtered fuel these are not trucks.

10k = Air, cabin & oil & oil filter.
20k = Fuel filter.

Use ONLY quality parts and oil. Your NB will love you for it.

Thanks for the replies.

We've owned this ALH car since new in 2000. It's been a great car.

I work as a diagnostician at a Nissan dealership and have for 39 years.

I know maintenance and our cars get it.

Will somebody please answer the question.... Why does the diesel fuel filter w/water separator have the ability to diminish fuel economy?

FranticFrank said:

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Will somebody please answer the question.... Why does the diesel fuel filter w/water separator have the ability to diminish fuel economy?

Click to expand...

Because once it fills up with sludge & the filter pores get blocked, then the fuel can't get through easily & you get fuel starvation.

(??I'm confused why you think a clogged fuel filter might not affect fuel delivery??)

MikeMars said:

Because once it fills up with sludge & the filter pores get blocked, then the fuel can't get through easily & you get fuel starvation.

(??I'm confused why you think a clogged fuel filter might not affect fuel delivery??)

Click to expand...

I agree a clogged fuel filter would affect fuel delivery, engine performance and eventually economy. The symptoms would be horrendous IMO.

This car has no driveability symptoms, at all. There is nothing to suggest the fuel filter IS restricted.

Wasting money replacing the air and cabin filter every 10K.
The air filter will go 40K easy in normal conditions. yes, I have a restriction meter on it.

PeterV said:

TDIs like clean filtered fuel these are not trucks.

10k = Air, cabin & oil & oil filter.
20k = Fuel filter.

Use ONLY quality parts and oil. Your NB will love you for it.

Click to expand...

VWBeamer said:

Wasting money replacing the air and cabin filter every 10K.
The air filter will go 40K easy in normal conditions. yes, I have a restriction meter on it.

Click to expand...

I replace mine every 20, like the owner's manual says. Wouldn't doubt you could go farther, especially if you clean it every 10k.

Of course we all should remember that there is a big difference between driving in Ohio and driving in dusty Georgia.

Everyone should remember to take local conditions and your personal driving situations when they are deciding on their personal maintenance schedule. I would guess that VW factors in some flexability.

"News flash! I found the IP timing off. The advance solenoid was running 29.6-30% and corrected it to 2.8 %."

What is the current setting now on the VCDS TDI graph...?

FranticFrank said:

Thanks for the replies.

We've owned this ALH car since new in 2000. It's been a great car.

I work as a diagnostician at a Nissan dealership and have for 39 years.

I know maintenance and our cars get it.

Will somebody please answer the question.... Why does the diesel fuel filter w/water separator have the ability to diminish fuel economy?

Click to expand...

Until the filter would become clogged enough to restrict fuel supply (at which time I think you would have some noticeable performance/drivability issues) it would possibly affect the pressure the IP could develope and not make for good injector firing, spray patterns, etc. I've yet to ever have a fuel filter get clogged and the one I took out of the '03 when I got it looked original (165K miles, original TB also-prior owner wasn't into maintainance) and upon cutting it open it was still very clean, although the canister was almost rusted out from the outside.
My fuel mileage has never improved from replacing a fuel filter, but as stated, I have never had a filter get clogged up.

dieselfuel, I got to the graph and found it a bit off. finally got it on the blue line and shows 1.5° BTDC.