Fuel mileage question

Being new to the TDI community, I bought a 2010 jetta, in hopes of getting great gas mileage. As I drive, I get roughly 35mpg, cruise is usually at 65-70ish. Not a heavy footed driver. Kind of lost in the diesel community here. Reading post and hearing people getting 40 plus, mpg. What am I doing wrong? 84k miles, and I do about 90 percent highway. Air filter is good. Any help would be appreciated. Thanks in advance

Do you have a manual or automatic transmission? Also check your tire pressure. A little over inflation (within reason) is good for mileage.

Automatic and I usually will keep the tires at 40, seeing how I drive so much HW.

What type of diesel do you use? Mine is like that when I use Biodiesel. When I use #2 Diesel it jumps to the upper 40's/gallon.

What RPM's are you seeing at cruising speed? Are you more towards 73-75 mph? I get 36 with my 14 Passat around town, but I've been having fun driving it. Do you have a modified ecu, or a tune installed? Assuming you're all up to speed on service, beyond just air filter. Also curious if you're running bio. You guys don't run bio in those 2010's do you?


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I use number 2, and I run a diesel additive to try and make it better , it may go up a bit but not enough to brag about. . Its all stock, no mods at all. Stock ecm. Was told by the dealership when I had an oil change, that I need to do the fuel filter, and water separator,would that cause almost a 10 mile per gallon decrease? guess you could run biodiesel in with them if you want to, I don't see what it would harm.

Not sure which engine yours has. My 14 Passat is supposedly not compatible with biodiesel. The warranty is void if you use anything more than a B5 or something like that, (except Illinois?) but beyond warranty issues, I was under the impression that it is to be avoided. I do run it in our 06 Jetta, and burn thousands of gallons on the farm, but not in the new rig.

You should change your fuel filter right away, just to rule that out.




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I have the 2.0. I just run 2 in it. There are some gas stations around here that say they have bio in them.
Yeah, I was thinking I should just do it anyway. Not sure when the last time it was changed or if even has been????? I'll find out soon enough. Possibly get it tomorrow. Where exactly is the fuel filter it self? Found the water separator. I just don't feel like going through all the panels underneath it and not finding it. Then have to put it all back together again. Are there any other things that I can rule out in reference to getting better fuel mileage. The only time I've ever seen better gas mileage, is in the morning when I'm not using the air conditioner and I have the cruise control set at 65.

The fuel filter, a.k.a. water separator, is one in the same. It sounds like you found it, but it is located on the passenger side just behind the headlight assembly, and you can't miss the the four fuel lines connected to the top of the filter housing. All you replace is the filter cartridge. With your engine, it is extremely important to purge air out of the fuel lines after replacing your filter using VCDS. Many on this forum will tell you to just fill the housing with fresh diesel and crank it over. I am not one of them.

Refer to the following DIY for more information:

http://www.myturbodiesel.com/wiki/fuel-filter-replacement-2009-vw-jetta-golf-jsw-and-audi-a3-tdi/

1) the DSG is going to hit you in mileage and will give you less than a manual. Say 3-5mpg

2) are you using cruise control or your foot, you can get better mpg with your foot IF you really pay attention to what you are doing. Otherwise it can actually detract from your mileage.

3) While on the highway how often do you use your brakes. If it's more than rarely, then that's probably a big part of your issue. Braking is nothing but lost fuel. Best economy is always looking well ahead and working to maintain a steady speed with absolute minimal use of brakes.

4) Do you pass pretty much at the same speed you're traveling or do you gun it hard and then coast or even brake?

5) How long are you on the highway?

6) Are you looking at your trip mpg or the current mpg?

7) Depending on how you drive before you get on the highway and how long you stay on it, you may find it takes awhile to get your trip average up there. If using the trip try resetting it sometime once you're on the highway and see what you're getting just on the highway. Maybe the issue isn't your highway mileage, but what you're doing before you get on.

8) What tires do you have on your car, size, make and model. This can drastically alter your mpg since rolling resistance and weight can very greatly from one type of tire to another.

9) How much do you carry in your car? This can matter depending on your driving style. With more variable speed, particularly involving braking it can directly impact your fuel economy.

Scoutx said:

1) the DSG is going to hit you in mileage and will give you less than a manual. Say 3-5mpg

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I'm curious as to where and how you came up with those numbers.

I recently posted on MPG on my 2104 vw golf tdi. I will tell you that my mpg has gone up. Iam getting 35-37 combined with 40-45 on the highway. How many miles you got on it? Also you need to learn the DSG to get the most out of your ride.

kcunniff said:

The fuel filter, a.k.a. water separator, is one in the same. It sounds like you found it, but it is located on the passenger side just behind the headlight assembly, and you can't miss the the four fuel lines connected to the top of the filter housing. All you replace is the filter cartridge. With your engine, it is extremely important to purge air out of the fuel lines after replacing your filter using VCDS. Many on this forum will tell you to just fill the housing with fresh diesel and crank it over. I am not one of them.

Refer to the following DIY for more information:

http://www.myturbodiesel.com/wiki/fuel-filter-replacement-2009-vw-jetta-golf-jsw-and-audi-a3-tdi/

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Great timing. I just purchased the filter and will attempt to DIM(yself). I'll be sure to read through your link first.

hybridkiller said:

I'm curious as to where and how you came up with those numbers.

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See the data in the monthly fuel economy data being collected.

cheoah said:

Not sure which engine yours has. My 14 Passat is supposedly not compatible with biodiesel. The warranty is void if you use anything more than a B5 or something like that, (except Illinois?) but beyond warranty issues, I was under the impression that it is to be avoided. I do run it in our 06 Jetta, and burn thousands of gallons on the farm, but not in the new rig.

You should change your fuel filter right away, just to rule that out.




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Correct, except Illinois and Minnesota (no others so far that I know of).
Owners of MKVI's in these two states have received letters that state VW will honor warranties with the use of up to B10 in IL (I think....IL people may correct this if it is wrong) and up to B20 in MN. Just have to watch the oil level.

Also, I have not noticed a drop in mileage since it changed over to bio. In fact, my record tank came using it, at over 54 mpg. Now that the weather is cooling off though.....normal hit in mileage to follow.

BeachBum-
I would consider 35mpg horrible for highway cruising. I have about 75% highway driving, and cruise at 70-80mph. I'm not out blowing the doors off of people, but I'm not hyper-miling, either. Just pretty much sensible, normal driving. If my FE was that poor, I'd be finding out what is wrong. Break-in does not account for it, or at least mine never did that poorly during early break-in. I think the effect of break-in on FE was more pronounced on pre-CR engines.

I'll leave it to those with DSG to comment on the difference that may make.

I reset my mileage when I got on the highway and got about 41, no ac, and using cruise at 70. I would say about 90-95% of my driving is highway. Moring commute is about 60 miles, 120ish, round trip.Im sure I past the break in period with 85k miles on it. I am very lost with diesel motors. I know gas, inside and out. Figured id try something different. ....lol, not working out the way I planned. But its clean though.ha

? Bump

Tire pressure? auto or manual? lots of hills (you're in florida so I'd assume that's a no)?

Can you confirm what RPM's you are maintaining at highway speed?


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BeachBumTDI, I wouldn't complain too much at 41 mpg on a CJAA. Given the sophisticated emissions system that ends up eating some mpgs, you're within the real-world range reported by others within this forum.

use DSG like manual?

does that help fuel economy more than just leaving it strictly in auto mode?

Ironman11142 said:

does that help fuel economy more than just leaving it strictly in auto mode?

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It should not make a difference. The reason DSG gets worse fuel mileage is due to 2 things:
More parasitic loss.
Shorter gear ratios.