All time low!

[DrewD]

I consistently get 43mpg in winter and 45 mpg in summer with 75-80 speed during my daily commute.

Today: 1000 miles into my 1500 trip to Florida from Colorado. I have gotten only 31mpg! This is my first foray into anything below 40mpg.

I do have two mountain bikes on a bike rack but didn't think they would cause a 30% decrease in fuel economy with cruise set on a hard 75mpg (5mph above their speed limit in Kansas and Missouri). I was battling high winds on my first tank and was not troubled by the poor mileage. However, the winds died down during my second tank and fuel economy was similar :-(

Any idea what could be causing the low fuel economy? BTW, on the highway the vehicle sounds great but at idle when I take a fuel stop, the car's idle is very rough ..it has never benn this bad before. I dumped twice the required powerservice concentrate in my last two tanks with no improvement in indle smoothness or stumbling and no difference in highway performance (its normal).

When I get to Florida,I'm pulling the filter and replacing it just to be safe. Is it possible the diesel fuel I got on the way may have been old or bad?

 

[wjdell]

My lifetime average is 42.7 or was - two trips to Melbourne at 72 mph and I went from 43 to 40. At 80 I get < 35 mpg, with no air brakes and 3 passengers. So if you had two air brakes going at a hard 75 then 31 may be about right.

Once you go above 2200 rpm in my car anyway the mileage goes down fast.
My best is at 1425 rpm 66 mpg and my worst was 35 mpg at 2800+ rpm.

 

[osomphane]

never heard of a "required powerservice"...

 

[Driver_found]

The bikes on the roof did it. I went down to @ 35pmg with three bikes on top. Just the rack alone sucked up @ 4 mpg.

-Mike

 

[buckeye96]

rough idle sounds like a filter issue. What about the air filter when was it changed last?

 

[IndigoBlueWagon]

It's not the bikes alone. I would believe 5 MPG for them, but not 12-15. A clogged fuel filter could be part of the problem. A rough idle may also indicate over-fueling, check your Injection quantity, although if it's 'way low you'd see smoke. Also check your snow screen and you may want to renew your air filter. Drive around some without the bikes and see what you get for mileage: then you'll have a realistic comparison.

 

[BMac]

My experience with a rough idle on a road trip ended up being failing DMF, however my milage did not change.

Bmac

 

[Fireblade_rr]

http://forums.tdiclub.com/showthread.php?t=202342

 

[Vipervnm]

I consistently get 43mpg in winter and 45 mpg in summer with 75-80 speed during my daily commute.

Today: 1000 miles into my 1500 trip to Florida from Colorado. I have gotten only 31mpg! This is my first foray into anything below 40mpg.

I do have two mountain bikes on a bike rack but didn't think they would cause a 30% decrease in fuel economy with cruise set on a hard 75mpg (5mph above their speed limit in Kansas and Missouri). I was battling high winds on my first tank and was not troubled by the poor mileage. However, the winds died down during my second tank and fuel economy was similar :-(

Any idea what could be causing the low fuel economy? BTW, on the highway the vehicle sounds great but at idle when I take a fuel stop, the car's idle is very rough ..it has never benn this bad before. I dumped twice the required powerservice concentrate in my last two tanks with no improvement in indle smoothness or stumbling and no difference in highway performance (its normal).

When I get to Florida,I'm pulling the filter and replacing it just to be safe. Is it possible the diesel fuel I got on the way may have been old or bad?

Hmmm, I'm not sure what the problem is but my Jetta typically gets 43 mpg on a road trip to NH in which I'll generally be going up and down mountains and averaging 80 mph. I don't ever have anything on the roof, but that seems like a stiff penalty to me.

 

[DrewD]

Got 33 mpg today over 800 miles. Still way below average I get on the highway. Tomorrow I will pull and replace the fuel filter.

Fuel filter has 12,000 miles on it and air filter has 4,000 miles on it.

Vehicle has normal power but takes more pedal to maintain speed than before.

 

[Joe_Meehan]

It does not sound that far off considering "75-80 mph" with bikes on the roof and add in you likely ended up with some winter blend on that trip.

Remember the faster you go the larger the penalty for the bikes. That said, replacing those filters is not a bad idea.

 

[DrewD]

Sorry for the misperception. The bikes are not on the roof but are on the back of the vehicle.

I'll be done with my trip today and will remove the bikes and trunk mounted rack and then do a quick 180 mile round trip to visit friends. Hopefully my MPGs will be back to normal.

 

[DRbillZ]

"ON THE BACK"
What you have there is a parachute! That is worse than being on the roof.

 

[dhdenney]

Just a side note, I can run my car at the 3K RPM range on the interstate and my mileage still doesn't drop much. I don't haul bikes though.

 

[MJ72]

You may have some poor quality diesel, but the drop in MPG has to be from the bikes. They have to be changing the way air is moving over and around your car while driving. Try holding your hand out the window at 75 MPH. While doing that consider how difficult holding a bike out your window at 75 MPH would be. It's going to drag down your MPG, especially at higher speeds. I think throwing two bikes on your roof and getting 31 MPG while driving at highway speeds is pretty good. How many other vehicles could do that?

 

[bulabula]

The lowest mileage noted in my sig (33 mpg) is due to having a couple of bikes on the Yakima rack during a 600 mile run.

Just having the rack onboard without any bikes netted a few mpg loss.

 

[MyAvocation]

A gasoline Metro is not even close to a diesel TDI. The intake restriction on you Metro changed the air fuel ratios, it does not work like that in a diesel.

Thanks Joe, post deleted.

 

[DrewD]

Took bike rack off for a 800 mile trip. I set cruise at 70mph and netted 43mpg.

On another trip with no racks, I got 49mpg at 65mph. I'm happy.