[xboxgod]

So my car went in the shop for service at the first of May and ever since then it has been getting very bad mileage. I took it back to the dealer for a couple small things and asked them to check it out. They basically said that if something was wrong, the SES light would be on. Since it's not, they are pretty much telling me "too bad". I log all my mileage and have since the day I bought the car. I know it isn't getting the same mileage, but I don't know how to get them to fix it. My car is right at 40,000 miles, so I have 10,000 miles to get this figured out. I have no idea what it is, but it is consistently worse since the service. They say all they did was air filter, fuel filter, and oil change. I don't want injectors or something major to go out at 50,800 miles. Any ideas?

Here is the mileage I used to get (41.7-43.5 mpg range):


Here is what I've been getting lately(30.5-32.2 mpg range):

[Mark M]

Couple random things, did they do any software updates when they had the car?

- Have you checked tire pressures?
- Are you now driving with windows / sunroof open? - ~2mpg
- Are you now driving with AC on? - ~2mpg
- Have you changed fuel stations / brands?
- Have you hand calculated to verify this decrease is accurate?

[AzureHaze]

That is strange. So you never had any fuel injector/DDE issues before? Double check your invoice to see if they did anything else other than maintenance?

I'd still strongly think about getting the extended warranty just for the peace of mind. I'm sure you already seen some of the '11 models posting their carbon build-up issues so we're not in the clear.

Average speed is 73mph? Damn I need to move back to Texas. I don't think I ever reached past 40mph!

[335dFan]

Frankly your current mileage seems more realistic. Being up in the low 40s is quite ambitious unless you are driving highway legal speeds with no winds and no traffic for the whole tank. At least that's my take on what a 335d is capable of. My best tank ever was 40 mpg on an interstate run from SC to MD, but usually around MD suburbia I am down around 30-32 mpg. My lifetime mileage is shown in my signature block, which does include a few hot rod runs (a track day and some tanks where I was driving a bit more aggressively).

[litxus]

Originally Posted by Mark M

Couple random things, did they do any software updates when they had the car?

- Have you checked tire pressures?
- Are you now driving with windows / sunroof open? - ~2mpg
- Are you now driving with AC on? - ~2mpg
- Have you changed fuel stations / brands?
- Have you hand calculated to verify this decrease is accurate?

+1

Research if other owners had similar experiences after a dealer visit. Not sure if it was 335d, but others mentioned before of crappy MPG after software updates. When I was looking on 335d it was a mixed bag, some indicated worst MPG after dealer visit, others had no change. Others noted that the main reason update was done is to help with soot, but a trade off was lower MPG.

[FormerRotor]

Originally Posted by Mark M

Couple random things, did they do any software updates when they had the car?

- Have you checked tire pressures?
- Are you now driving with windows / sunroof open? - ~2mpg
- Are you now driving with AC on? - ~2mpg
- Have you changed fuel stations / brands?
- Have you hand calculated to verify this decrease is accurate?

+2

26 miles is far too short of a sample to determine anything, And I would agree with @335dFan that the latter seems more realistic if you had a real sample, but it never hurts to ensure that you are up to date on maintenance!

When was your last oil change? have you tried any injector cleaner like bg 244k? Did you replace the engine air filter yet? How about the fuel filter? (You should be getting ready to replace each of these for the second time now). Verified that the MAF sensor is clean?

At 40k miles, may want to have your intake checked for carbon once you've exhausted the above options and those in Mark's post, but this will be out of pocket.

[xboxgod]

So maybe I need to elaborate. I read the invoice/receipt and they only did air filter, fuel filter, and oil change. I had them do the gearbox update many months ago when it was first out.

On the mileage, I was getting 32-33 combined (across the whole tank) driving normally with not much effort. I am now struggling to get 28-29 combined. So my daily drive to work is down 10mpg, but my overall combined is down 4-5mpg. I do keep track of EVERY tank of gas in an app and do not rely on the iDrive for my mileage.I used to get 530 miles out of a tank and now I'm getting like 465 max.

- Have you checked tire pressures? Tires are consistent.
Just had it in for an alignment.
- Are you now driving with windows / sunroof open? - ~2mpg
Never open them
- Are you now driving with AC on? - ~2mpg
AC is always on for the most part. It is set to auto and on 72
- Have you changed fuel stations / brands?
Nope
- Have you hand calculated to verify this decrease is accurate?
Yep.

The MPG needle used to sit close to 50mpg when driving to work and I am now struggling to keep it above 30mpg. I have this happen on windy days, but usually driving back the opposite direction has the opposite effect since the wind is pushing me. This is not the case here. Windy or not, it does this.

I guess I'll have to have the intake checked for carbon and see what I can find out.

P.S. - The car has different wheels and the VSS is off by 3mph, so 73 is actually 70. BUT 70moh is waaaaaay better than 40mph. I can't imagine never going over 40. Haha

[FormerRotor]

Originally Posted by xboxgod

So maybe I need to elaborate....

P.S. - The car has different wheels and the VSS is off by 3mph, so 73 is actually 70. BUT 70moh is waaaaaay better than 40mph. I can't imagine never going over 40. Haha

Ding ding ding!!! we may have a winner!

What is the new wheel/tire setup & what was the old?

[F32Fleet]

Originally Posted by 335dFan

Frankly your current mileage seems more realistic. Being up in the low 40s is quite ambitious unless you are driving highway legal speeds with no winds and no traffic for the whole tank. At least that's my take on what a 335d is capable of. My best tank ever was 40 mpg on an interstate run from SC to MD, but usually around MD suburbia I am down around 30-32 mpg. My lifetime mileage is shown in my signature block, which does include a few hot rod runs (a track day and some tanks where I was driving a bit more aggressively).

This

[Mark M]

Another thought I had. Perhaps your car has been trying to do a DPF regen but has been unsuccessful at completing it due to short drive cycles? I read one article where a user stated his regen took over 20 miles at steady rpms to complete. Not sure how the regen works, but I read it uses more fuel to create the heat needed to cook off the soot on the filter. If it is a separate diesel injector in the dpf or if it is just greater fuel metered in through the cylinder injectors, I don't know. Just brainstorming at this point.

[AzureHaze]

Originally Posted by xboxgod

P.S. - The car has different wheels and the VSS is off by 3mph, so 73 is actually 70. BUT 70moh is waaaaaay better than 40mph. I can't imagine never going over 40. Haha

Well I do go over 40 from time to time but it's just the afternoon traffic during the weekdays that kills my average mph. I even get off work earlier than the average worker and the freeways are still jam packed! Who are those people on the road seriously...

[335dFan]

Originally Posted by AzureHaze

Who are those people on the road seriously...

Yeah, I agree. I thought we owned the road. Who gave them permission to mess with our driving experience? I also hate it when some slowpoke is interfering with my taking a high speed corner. It just ain't fair. And that's what causes our carbon build up....all these other drivers using our roads.

[xboxgod]

Once again, not to be rude, but let me go over a couple things.

- I didn't come here to have people decide which mileage was better, current or previous. Telling me I don't have a problem because you think that's the mileage I SHOULD get is ignorant. It used to get better mileage and now it gets worse. The actual numbers are variable. That is my problem. I fully understand where the mileage SHOULD be as I am not an idiot. I have never gotten over 33.6mpg COMBINED. My current "lifetime" number is 29.6mpg. I also understand that this car is only supposed to get 27mpg COMBINED mpg. I am trying to detect a problem before my warranty expires so I don't get stuck with a massive repair bill. That is the point of this post.

- Again, I am aware that these cars get close to my 2nd number COMBINED. I reset my iDrive mileage every single day at the same point to track what I am getting each day and I don't reset the one on the dash until fill up. This is how I KNOW there is an issue.


Mark M - That is worth a look. Thank you for useable information. Both of your posts were right on par with what I was looking for. And nice e30. I also have a 1991 318is.

AzureHaze - Might need to do the extended warranty. Read it was like $6000 for powertrain. $2500 for maintenance only. I think they have a finance option for it though. Haha

FormerRotor - The car was delivered with the 5 spoke 287 wheels instead of the M Sport 193 wheels. The dealer claims this is why the VSS is off. I am not sure how true that is since they are both 18" wheels, but GPS verifies a 3-4 mph difference.
I also need to try an injector cleaner.

litxus - I remember that update. I think that was for the older 335d's and was already applied to the newer ones. I'd have to go back and re-read the posts.

Sorry to be so "upfront", but I hate when a post takes a nasty turn because someone throws it off-topic with stuff that doesn't relate to the original post.

[joe_planet]

I think Mark M is onto something.. this is the only thing I can think of. I also have a diesel truck and I dont typically drive it long distances. Well one week I think I saw that regen message a dozen times.. then I said fk it and drove it to work which is 60 miles one way, lol. Finally it quit the regen. It even popped up a message saying regen is completed.
Can you try to drive it maybe an extra 20 minutes and see what will happen?
I'm getting between 30~34mpg avg on my d but this is driving 80~85 and 90% highway, so I'd definitely say your mileage is on the low side right now.

[Puerto Rican 335d]

xbox I am with you even though you changed your wheels this cannot be the problem the most is losing 2mpg but almost 10 mpg is something to worry about even if the SES light aka IDIOT light does comes up or not!! something is going wrong. Try using cetane booster and injector cleaner and BEAT the sheit out of her for a least to runs at 150 mph and she'll loosen up thats what i did to my car and Ive gotten better mileage since then

BTW that was last December when we ran the 1/2 mile here in Puerto Rico

[Mark M]

xbox.....here is a great article on the operation of a dpf and regen cycles......albiet this is from the VW community but believe much is similar for us.

http://uk-mkivs.net/forums/t/343695.aspx

[floydarogers]

Originally Posted by xboxgod

- I didn't come here to have people decide which mileage was better, current or previous. Telling me I don't have a problem because you think that's the mileage I SHOULD get is ignorant. It used to get better mileage and now it gets worse. The actual numbers are variable. That is my problem. I fully understand where the mileage SHOULD be as I am not an idiot. I have never gotten over 33.6mpg COMBINED. My current "lifetime" number is 29.6mpg. I also understand that this car is only supposed to get 27mpg COMBINED mpg. I am trying to detect a problem before my warranty expires so I don't get stuck with a massive repair bill. That is the point of this post.
...
AzureHaze - Might need to do the extended warranty. Read it was like $6000 for powertrain. $2500 for maintenance only. I think they have a finance option for it though. Haha

Except that you hadn't explained (with the text I italicized) the real situation. Don't blame us for poor communication in the original post: we were ignorant of the complete situation. The addition of a single sentence BY YOU would have clarified things immensely. (One of my tenets is "always assume that it's your fault", with "your" being self-referential.)

A regen takes 5-10 minutes; it uses post-combustion injection to run. Shouldn't cause that much lower mileage, over a 23 minute commute that includes a regen.

Extended warranty (there are three levels) for 2 additional years/100K miles platinum (no radio/iDrive) should be around $2500-$2800 if you beat up the dealer (they initially quoted me $3400 but came down right away.) Lowest I've seen is around $2500.

[xboxgod]

Thanks guys. I will try some cleaners/additives and see if I can get my local shop guy to check for carbon build up. I will read that regen article also.

joe_planet - I drive mostly highway too. I live right off the highway and work right off the highway. All DNT, GB, 380, and 114. That's another reason why I'm concerned.

[sohcpunk]

Your current MPG is what everyone here is getting. Being in the low 40s sounds like something is wrong with your car. Maybe your car fixed itself.

[Mark M]

I agree with the OP. To the rest of you, beleive you are not looking at his full screen shots. His mpg measurements are not on an entire tank. Rather they are repeat measurements of his commute. (Segment measurements) Which some would argue is a more accurate and indicative way to measure as you have fewer variables which you would have across an entire tank of fuel.

It is totally realisitic to get 40+mpg segment mpg. I did it yesterday in mine on my commute, 42.7mpg over my morning 34 mile commute.

[xboxgod]

Originally Posted by sohcpunk

Your current MPG is what everyone here is getting. Being in the low 40s sounds like something is wrong with your car. Maybe your car fixed itself.

Is it because you are a "Second Lieutenant" and feel like being an a-hole that you posted this? Or are you having difficulty comprehending the issue? If you have no valuable input, please refrain from posting on people's threads. I literally JUST went over this.

[FormerRotor]

@Mark M, I'm glad you're on board,brother. Your knowledge, research, and approach are going to prove hugely valuable to the diesel group.

Originally Posted by xboxgod

FormerRotor - The car was delivered with the 5 spoke 287 wheels instead of the M Sport 193 wheels. The dealer claims this is why the VSS is off. I am not sure how true that is since they are both 18" wheels, but GPS verifies a 3-4 mph difference.
I also need to try an injector cleaner.

Sorry to be so "upfront", but I hate when a post takes a nasty turn because someone throws it off-topic with stuff that doesn't relate to the original post.

Well (as you likely already know) the specs on these two wheels are exactly the same...
F 18x8 ET34. 11.23kg
R 18x8.5 ET 37. 11.93kg
...And come with the same size tires, thus, unless there was some HUGE discrepancy in tread depth, I would believe your skepticism in your dealers remarks to be well-based. Unfortunately, this also rules out the wheels as a possible culprit unless you changed the rubber significantly which I don't believe you did based on your previous post about the tires.

FWIW (and its worth nothing as I am but an Internet stranger),I understand what you are saying, but I think some of your responses have been a bit brusque. I think most folks are attempting to be helpful and no one has taken the thread too far off track. Curbing the negativity tends to make participation in a thread much more pleasurable.

I seem to remember you researching tunes and I believe you were running JBD at some point (based on your post history). Are you still running JBD? I see no mention of it in this thread, thus I assume you are not still running it but--If so...

• since what mileage have you had it plugged in?
• Has it been unplugged at any point during or directly preceeding your sample period?
• Have you tried removing it for a few tanks to see what affect it has on your mileage?

Some additional questions...

• Do you log any other data beyond gas mileage? Most folks do not, but this can be helpful with getting to the bottom of such matters as those you are describing. I often find myself wishing I had access to more historical data for my vehicle.
• Ever been on a dyno? See any degradation there?