I'm concerned in a possbile change in performance. Would appreciate some input.

[Fla_Panther]

Hi all,

I bought my TDI around Christmas of last year, and my mechanic friend went with me when I bought the car ... but he's not a VW mechanic so I took the Jetta to this mom & pop VW shop a few blocks away to let him look it over. I'd always heard good things about the place but something about the visit felt off.

I was holding off on doing the first oil change because my friend and I were going to swap out the CV joints/axles ... due to delays in our schedules I decided to allow the shop a few blocks away do the oil change.

That was last weekend. Ever since I've noticed wide fluctuations in my average MPG rating. Prior to taking it to the shop it was steady between 34-37, and now it's fluctuating from as low as 20 up to 40. At first I wondered if I'd switched the display from average to actual but no, I still have that circle with the line through it. I'm not sure what might be causing this, but I'm concerned, never had a TDI before and never had work done at this shop before. My driving habits are no different now than they were a week ago ... even if I was driving slightly differently I doubt it would affect my MPG that much.

Thoughts?

 

[Joeym4692]

Make sure that they used the correct oil first off.
If this is the 2010 TDI you have listed on your profile it must use 507.00 oil.
This is very important as using the wrong oil can cause problems with your emissions equipment.

 

[South Coast Guy]

The only accurate way to measure fuel consumption is the old-fashioned way. Divide miles driven by fuel used. Do it several times to develop a meaningful average.

 

[Fla_Panther]

But how would I find out after the fact? I'm sure if I call up there the guy's going to say he did use 507. Is there a way to check the oil itself?

 

[nord]

And now you know exactly why you either stay at the shop when the work is being done or do it yourself... Trust, but verify!

Unless you do mostly stop and go driving I'd opine that your average economy even before you noticed the current drop was bordering on terrible. Your Jetta should be easily bumping above 40 mpg. EASILY!

If you have any questions about the oil, then dump it. You need to be 100% sure of what's in your crankcase.

Poor performance? First order of diesel business is clean filters. Change them. While you're at it you might check for "sparkles" when you remove the fuel filter cap. Sparkles are not a good thing and tend to indicate a failing HPFP.

The incorrect oil (if this be the case) will not harm the car to any great degree. All the same you need to use the correct VW spec lubricant. I'd suggest that you find someone nearby with VagCom as there may be pending codes. Too many things are at play to say much other than the above.

 

[Fla_Panther]

Your Jetta should be easily bumping above 40 mpg. EASILY!

Well, let's clarify something. The display can either show show ACTUAL MPG (what the car is getting right that second), or AVERAGE MPG. I haven't yet looked into how the car calculates the average. At first I thought it would reset when I reset the trip meter (which I do every time I refill so I can write down actual milage and figure out actual MPG), but I've reset the trip meter a few times already and there was no great change in the average until now.

Up until now it was ranging as high as 80mpg when set to display ACTUAL MPG, but when I set the display to show AVERAGE MPG it was 34-37. Now the car is ranging from 20-40 when displaing the AVERAGE. The only other thing I can think of is that the shop did something to reset the timeframe that the car is calculating the average from.

If you have any questions about the oil, then dump it. You need to be 100% sure of what's in your crankcase.

Great. If I really do have to do all th work on this car myself it's going to be a huge PITA. Due to my schedule and commute my week is effectively shot and my weekends are already busy enough as it is. I don't have a good area to work, nor a good set of tools right now. I'm planning on renovating the house I just bought to add a garage but that's probably a year or two away. This may not be the right car for me at this point in my life.

Poor performance? First order of diesel business is clean filters. Change them. While you're at it you might check for "sparkles" when you remove the fuel filter cap. Sparkles are not a good thing and tend to indicate a failing HPFP.

Yeah, I've read about the HPFP issue. Really praying it's not that. I've only had the car for 4 months, havent' had time to put the mods on it.

The incorrect oil (if this be the case) will not harm the car to any great degree. All the same you need to use the correct VW spec lubricant. I'd suggest that you find someone nearby with VagCom as there may be pending codes. Too many things are at play to say much other than the above.

I found a thread with a list of people in my area, found 5 and emailed them, 3 bounced back as undeliverable. Hope one of the other two will respond.

 

[nord]

Quote:
Originally Posted by nord
Your Jetta should be easily bumping above 40 mpg. EASILY!

Well, let's clarify something. The display can either show show ACTUAL MPG (what the car is getting right that second), or AVERAGE MPG. I haven't yet looked into how the car calculates the average. At first I thought it would reset when I reset the trip meter (which I do every time I refill so I can write down actual milage and figure out actual MPG), but I've reset the trip meter a few times already and there was no great change in the average until now.

Up until now it was ranging as high as 80mpg when set to display ACTUAL MPG, but when I set the display to show AVERAGE MPG it was 34-37. Now the car is ranging from 20-40 when displaing the AVERAGE. The only other thing I can think of is that the shop did something to reset the timeframe that the car is calculating the average from.

Fill to fill with recorded gallons and miles is really the only truly reliable method of calculation. For the record our NMS Passats are bumping 50 mpg right now. This depending on weather and temps.

Quote:
Originally Posted by nord
If you have any questions about the oil, then dump it. You need to be 100% sure of what's in your crankcase.

Great. If I really do have to do all th work on this car myself it's going to be a huge PITA. Due to my schedule and commute my week is effectively shot and my weekends are already busy enough as it is. I don't have a good area to work, nor a good set of tools right now. I'm planning on renovating the house I just bought to add a garage but that's probably a year or two away. This may not be the right car for me at this point in my life.

You don't have to do the work but you do have to be responsible. Find a shop that does things by the book. Word of warning... Our local shops don't.

Quote:
Originally Posted by nord
Poor performance? First order of diesel business is clean filters. Change them. While you're at it you might check for "sparkles" when you remove the fuel filter cap. Sparkles are not a good thing and tend to indicate a failing HPFP.

Yeah, I've read about the HPFP issue. Really praying it's not that. I've only had the car for 4 months, havent' had time to put the mods on it.

Do the important things first. If you have time for mods, then you have time to properly maintain the vehicle. Your Jetta is a great car as long as you don't attempt to cut corners or outsmart the engineering.

Quote:
Originally Posted by nord
The incorrect oil (if this be the case) will not harm the car to any great degree. All the same you need to use the correct VW spec lubricant. I'd suggest that you find someone nearby with VagCom as there may be pending codes. Too many things are at play to say much other than the above.

I found a thread with a list of people in my area, found 5 and emailed them, 3 bounced back as undeliverable. Hope one of the other two will respond.

Good idea.

 

[Fla_Panther]

Do the important things first. If you have time for mods, then you have time to properly maintain the vehicle.

I'm not sure how to interpret that. It sounds like you're saying there are more important maintenance than the mods. If you're referring to things like oil and filter changes, I agree, but if you're saying that proper maintenance will help me avoid the HPFP issue I'd like to hear more about that because from what I've read even people who've kept a close eye on their fuel and oil have had the HPFP blow up on them.

Your Jetta is a great car as long as you don't attempt to cut corners or outsmart the engineering.

And that sounds like you might be advising me not to do the mods. Again, if so, I'd like to know why not. Like I said, from what I've read so far simply doing regular maintenance isn't enough to avoid an HPFP failure.

 

[nord]

Your car your decision. All I'm getting at is if you don't have the time to do basic maintenance then I question whether mods are a good idea.

And, yes, I'm generally against most modifications.

 

[Joeym4692]

As far as the whole shop thing goes. You can always buy the oil and have it shipped to your house off of a few websites or pick it up at the dealer.
When you go to change the oil at the stop hand them the oil and simply tell them thats what you want to go in the car.
Just keep after maintenance and the car should last you quite some time.

 

[eric-satx]

I know not all MFDs are equal, but my BRMs have 2 average mpg displays and a real-time mpg. The first average will reset after the key is off for 2hours. I read somewhere that the "long term" mpg average will reset after 9999 miles.

Some possibilities:
- by coincidence, your car just reached a 9999 mile interval and reset.
- the shop may have accidentally reset the "long term" average. If so, it will settle down in a few days.
- you may be looking at the "short term" average mpg. Which will fluctuate wildly the first couple of minutes you start driving.

 

[DriverJon]

I also am wondering a bit about your description of the fuel consumption gauges and what your seeing on them. They may vary from car year to year, but I have a 2010 Jetta as well... (early Jan)

Excuse the following longwindedness... just in case you don't already know each of these and what exactly they're doing.

So, what I have is this... There are two averaging fuel consumption meters, marked 1 and 2. These take a cumulative average MPG. 1, will reset if the car is turned off for 1-2 hrs. I look at it as a trip MPG average gauge. 2, wont reset until you do. (or probably when it wraps around at 999 mi) I reset at the fill of every tank, and use it as a tank average gauge.

Thirdly, there's a different gauge, not the long average, on a different display page, and it shows the more instantaneous MPG, or averaging only every 2 seconds or so.

Now, on to something you want to hear... I will see a wide range of numbers on the instant average, from down into the 10's, or even single digits, when really flooring it, especially when not moving fast yet.. due to real, actual 10mpg momemts. And, when rolling or going downhill with my foot off the pedal, I see ---, which is representing infinite MPG, 'cause the fuel cuts off. Actually, it will read up to 200mpg, and above that goes to ---. A couple years ago it always read 200, no matter what, but a ECU flash was put out and it changed.

Typical flat ground freeway cruising, 70mph or so, I'll see 43-48mpg. With the bumps up to triple digits, and drops to the mid to low 30's, depending on traffic, inclines, downhill sections, etc. If you don't see something like that under those conditons, something isn't right...

The only real way to know true MPG, of course, is to log the mileage, and log the tank, and calculate. (I reset the external trip odometer at tank fills, too, for a better miles traveled number) I get plus or minus an MPG or two from calculated to the #2 tank average, more typically about 1-1.5 MPG high than the calculated. Pretty accurate. YMMV, but log several tanks and you'll know how close yours is.

Probably more info than you were looking for, but hope that helps...

 

[Fla_Panther]

Okay, that sounds like some of the information I was looking for, and guessing on. Do you know how to switch the display between the two trip-averaging modes? I know how to switch it from the 2-second update to the trip average but didn't see anything indicating the third selection when I was playing with the display settings. Guess I need to make a note to order an owner's manual this week.

 

[Dragracerzzz]

My 06 BRM when the pedal is floored on a county highway will give a instantaneous reading of as low as 7-8 MPG's and and when cruising with light pedal it will read up to well over 100 MPG's. All that matters is the numbers you come up with when figuring miles from your last tank, averaged out over time. Good luck
DRZ

 

[meerschm]

The accurate info on the mpg and other displays are in your owners manual. if you do not have one, you should consider getting one.

(and reading it)

good plan.