help with poor mpg

jahfakin

Well-known member
Joined
Jun 24, 2002
Location
Philly
TDI
99.5 VW NB TDi (techno blue)
i have a 99 NB 5 speed with <35K miles.
I bought it over the summer. Lately I have been getting 35mpg, what's wrong? I know on the highway, the car gets like 40-45 mpg at 80-85 mph ,based on those long road trips. but the problem is when i do city driving, the mpg falls off badly. i know i'm kinda heavy footed, but still. i also know winter fuel gives poor fuel economy, but not that much. today i put in 12.640 gals for 452 miles of driving, i vent.

The car drives great, no mods except mufflerectomy and foam air filter.

Any advice from you veterans on how to drive this car in the city for the best possible fuel economy or performance?? what rpm to do experts shift at?? i know shifting too low will lug the engine. but i don't want to drive sooooo slow that the guys behind me are gonna want to run me over with their H2 Hummers.

any advice is great. i'm not really complaining, my 4.6L Stang gets like 17 mpg in the city, so the TDi is a dream, dispite the current bad fuel economy.
 

paul_cat

Veteran Member
Joined
Apr 4, 2001
Location
Bowie, MD
TDI
2001 Golf TDI [ALH]
1) mileage will drop w/ winter fuel, expect that.

2) up shift at 2500 rpm, even less 4th to 5th.

3) don't ever downshift to slow the car down, just
brake normally. When stopping (as for a light) don't pop clutch 'til rpm gets down to 1000. When slowing and continuing downshift at about 1500 rpm.

4) "85 mph on the highway" will not give you 45 mpg! Try keeping it around 65 if mpg is your main concern. 85 is fun, but not fruggle!

Remember, this is a low rpm high power motor, you don't need to wind it out like a sports car to get the power. [Tho it should wind into the 4000's without a wimper; try it occasionally to blow out the carbon and test your MAF]. On the highway, passing in 5th is the way to go; just floor it, it should go fine without downshifting.
 

Milehog

Veteran Member
Joined
May 9, 2001
Location
Northwest US Connecticut
TDI
2013 Jetta sports wagon TDI
jahfakin,

I'm no expert, but with my 01 Jetta the lowest I have seen this winter is 46.3 mpg. I routinely down shift (although there's not much engine braking from a diesel) and have a heavy foot off the line. Just love the torque. I suspect, your ride, which I assume was purchased used, has a problem. Not knowing it's history it could be a clogged intake, timing, or a MAF going south (or just dirty). If you have not checked make sure the intake snorkel screen is clean as well as the air filter. Also the length of your drive may be a factor. I drive 50 miles one way to work and it takes 7-8 miles in this really cold weather for the engine to produce cabin heat let alone reach operating temp. Just some things to consider!
 

Nitejav

Veteran Member
Joined
Apr 1, 2002
Location
North Wales, PA
TDI
NiteJav
My econ has tanked since I came back to philly. A lot of it has to do with the winterized diesel fuel. I drive pretty much the same way as you going 80-85, and many times much faster then that. If you hold 70 on the highway and cruise, you should get about 50mpg. The more you raise the speed from their the worse it will get.

Add philly's stop and go traffic, and stop and go at lights, and you have a perfect formula for some sub-par mileage. I would also look at the fuel your getting, their is a Hess at Grays Ferry which is pretty good from what I know. I think some one else on this forum knows where you can get some 50 cetane diesel at an Amaco station off of route 1.

Normally averageing about 80-85 I will get about 43-44mpg in the summer. I have never spent the summer in the city with this car yet, so I have no mileage observations for you in that catagory.
 

eetsoot

Veteran Member
Joined
Dec 15, 2001
Location
Oxnard, Ca (at least for now!)
TDI
Jetta, 2002, galaxy blue
I'm a little on the heavy footed side too. I average around 44mph. On long trips with cruise set @ 75 I get 49-50. This weekend in driving up to a GTG I did spend some time at the 100+ mph range(according to the MFA my average speed for the tank was 85) and only got 39mpg.
My worst tank ever was 38 mpg, I was racing every ricer I saw.
 

jahfakin

Well-known member
Joined
Jun 24, 2002
Location
Philly
TDI
99.5 VW NB TDi (techno blue)
according to the MFA my average speed for the tank was 85) and only got 39mpg
<font size="2" face="Verdana, Helvetica, sans-serif">i had no idea that driving that fast would hurt your mpg that much. And that's on winter fuel. so i guess i just got to take it easy on my ride a bit. i do some short trips, like on the weekends to run some errands, and i know that hurts me even more, since the car doesn't warm up.
 

79Wabbit

Member
Joined
Jan 26, 2003
Location
New Jersey
TDI
New Beetle
I just picked up a 2000 Beetle TDI in late november. Once I learned how to really use the power the TDI puts out I've been getting around 30MPG in town. Mostly because I will rev it up to 3800RPM or so before shifting. When I just drive normaly I tend to shift 1st around 2250, 2nd around 1900, the about 1500 for 3rd and 4th. Driving like that in town nets me about 51MPG.

About 2 weeks after I picked up my Bug I took a little road trip to see my sister in CT from OK. 1588 miles later, round trip highway miles, I averaged 50.26MPG and 74.35MPH
 

Derrel H Green

Top Post Dawg
Joined
Jun 2, 2002
Location
Murrieta, California
TDI
An '05 MBZ E-320 CDI (W-211) replaced the '10 TDI JSW
Originally posted by jahfakin:
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> According to the MFA, my average speed for the tank was 85 and only got 39 MPG.
<font size="2" face="Verdana, Helvetica, sans-serif">I had no idea that driving that fast would hurt your mpg that much. And that's on winter fuel. [NOT] so I guess I've just got to take it easy on my ride a bit. I do some short trips, like on the weekends to run some errands, and I know that hurts me even more, since the car doesn't warm up.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">


gedster has big injectors (0.205s). Probably using ECD-1 ULSD fuel which will drop mileage at least 2 percent.


Califonia fuel is not winterized to the best of my knowledge, at least in SoCal.


 
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