Not very good fuel mileage

I see people getting like 700 miles on one tank and mine only gets 320ish. What am I doing wrong?

and Your Tank is on EMPTY at 320ish?

TDI smile said:

and Your Tank is on EMPTY at 320ish?

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Yes just about

I've been having similar issues (not as bad) with my 01 Jetta 5-speed where I'm only averaging about 40mpg and I've been slowly eliminating the things that are the usual causes. Hopefully I can save you some of the research I had to do and with some luck one of the Gurus will chime in. Here are a few things to check/consider:

Is it a manual or automatic? The Mk4 auto transmission (pre-DSG) was nothing to write home about mileage wise.

Is the engine reaching proper operating temperature? If the needle takes forever to get to vertical or if it heats up but doesn't quite to straight-up/down than you're engine isn't warmed up properly and it could be a temp sensor (easy) or thermostat. That effects mileage.

Are all of your filters relatively new? (air/fuel)

Tires and tire pressure can have an effect but not to the extent you're describing.

Finally, are you sure the transmission is the right one for the car? Mk4 trannies are interchangeable but not all geared the same way. I know of a case where someone bought a Mk4 TDI that had a 2.0 gasser box in it and it revved WAY too high on the freeway. Check the code stamped on the top of the transmission near the gear tower, if it's for a TDI it will have either EBJ, EGR, or DQY code stamped on it.

I'm still scratching my head over why I'm still only getting 40mpg. I just bought a Scangauge and with Cruise Control on, driving on the freeway, I'm only averaging about 38 and I'm not sure why. I'm thinking it may be the MAF sensor so if anyone reading has any ideas, I'd be very appreciative.

One thing to note is what RPM you're turning at a given highway speed, say 100 kph/65 mph. That alone will give an indication of how the tranny is geared.

My wife drives the Mk4 with an auto... unfortunately she does 75% city so she gets roughly 35mpg out of it...

If I drive it gently for a week, mostly highway, I can get 38-40mpg but that's about it from the 01M tranny... best ever was 42mpg on a road trip.

ketchupshirt88 said:

My wife drives the Mk4 with an auto... unfortunately she does 75% city so she gets roughly 35mpg out of it...

If I drive it gently for a week, mostly highway, I can get 38-40mpg but that's about it from the 01M tranny... best ever was 42mpg on a road trip.

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I had a '03 Jetta automatic. I hypermile, but could not squeeze better than 36mpg highway out of it. My 1988 Honda CRX HF got 50+ on the highway. Some people do better with automatic transmissions, but I can't explain it.

Mike in Anchorage said:

One thing to note is what RPM you're turning at a given highway speed, say 100 kph/65 mph. That alone will give an indication of how the tranny is geared.

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at 65 mph my rpms are at about 2,100. It seems pretty normal to me.

That does indeed seem normal, so no slipping in the tranny.

charlieruu said:

I see people getting like 700 miles on one tank and mine only gets 320ish. What am I doing wrong?

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Empty to full is around 14 gallons at the pump?

Your fuel delivery system could be messed up. We had an aircraft that would dump fuel overboard due to a broken fuel line, and looked like it was consuming much more fuel than it really was.

I get around 34-36mpg delivering pizza. I know my injectors are shot and turbo is sticky tho. I was getting like 18mpg when I first got it in dec but I've put w couple grand into it fixing up things getting to where I am. After a tune and injectors I should get 40ish


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Have you done a ventectomy yet? At least then you will know that the tank is actually full when you fill.

Also, the autos seems to very a lot from car to car. I've seen people getting as low as 30mpg, and I was getting as high as 48mpg (50mpg one time).

Do the ventectomy if you haven't already. You can find a write up in the forums. Check tire pressure also. That can really help. I run the max sidewall of the tire. Perfectly safe to do so.

Does anyone know what might cause over-fueling at highway speeds? My 01 ALH 5-Speed averages in the 35-37 mpg range (according to my ScanGauge) on flat surfaces at 60mph with the windows/roof close, no AC, tires at max pressure per sidewall. I've replaced the thermostat/coolant sensor, filters, new EGR valve, etc. The IQ is at about 3.0 at idle which is what I've read is normal but I'm wondering if that setting (done by the Hammer Mod with the VCDS running) is wrong. I feel like on the flats at 60mph I should be seeing higher averages.

Sharkey said:

I feel like on the flats at 60mph I should be seeing higher averages.

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Maybe so, but what are you getting when you hand calculate the MPG? Check your odo with GPS, and do a couple full tanks and hand calculate MPG. Forget about what the Scangauge is telling you. Also, don't worry about IQ so much...focus more on timing. Make sure engine base timing is correct, and then advance from there.

As for the OP only getting 320 miles to a tank? Assuming that's a 14 gal fill-up, that's almost 20MPG...the diesel would have to be pouring out of the tail pipe or pouring out of the fuel tank. I'd be checking all the basics such as timing, tune-up items, anything that create drag (brakes, etc) and confirm the odo with GPS.

Thanks Rembrandt, I'll look into the timing.
Cheers!

Rembrant said:

Maybe so, but what are you getting when you hand calculate the MPG? Check your odo with GPS, and do a couple full tanks and hand calculate MPG. Forget about what the Scangauge is telling you. Also, don't worry about IQ so much...focus more on timing. Make sure engine base timing is correct, and then advance from there.



As for the OP only getting 320 miles to a tank? Assuming that's a 14 gal fill-up, that's almost 20MPG...the diesel would have to be pouring out of the tail pipe or pouring out of the fuel tank. I'd be checking all the basics such as timing, tune-up items, anything that create drag (brakes, etc) and confirm the odo with GPS.

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I wish I could do a fill up in mine. It spews out the last 2 gallons or so from somewhere above the tank. Everything on the top including the big seal is all dry when it does this. I've been told the ventectomy would solve this but we have a Jetta that does the same and it has had that done.


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AnotherPerson said:

I wish I could do a fill up in mine. It spews out the last 2 gallons or so from somewhere above the tank. Everything on the top including the big seal is all dry when it does this. I've been told the ventectomy would solve this but we have a Jetta that does the same and it has had that done.

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I don't know where it might be coming from, but it sounds like a leak in the filler neck somewhere? I have both cars vented, and can fill both of them to the cap. I even fill them and leave them overnight like this once in a while, although I try not to.
My 2000 Beetle usually takes about 14.5 gallons to fill, and with that I have been getting about 715-720 miles every tank. My Golf will take 16 gallons, and will hit about 750 miles mixed driving and once in a while 800 if I'm doing full tanks on the highway.

If the ventectomy was done incorrectly, such as removing the entire valve assembly instead of the guts of the assembly, it could be siphoning off fuel when going down the road. It would also explain the last two gallons when filling the fuel tank.