How much difference can temperature make?

[CALL911]

So I purchased my 2001 Golf TDI last fall, and have been averaging at best 52 ish MPG (55 and 60 MPH to and from work). It has been fall and winter since I got the car, so it really hasn't seen much warm weather.

Last week, there was a slight heat wave, and temps got in the mid 50's Farenheit. I noticed that my MPG was better, and sure enough with my fill up, I got 58 MPG!

My question is, what is the most ideal temps for MPG? I know these cars are more efficient the warmer the engine temp is, and I would think the warmer it is (especially away from near freezing temps) the better the mileage would be. What kinds of improvements can I expect to see in the summer when it is 75 Farenheit?

On another note, I purchased a scanner with a TDI buddy, and recently found that my timing was low. We plan on increasing the timing to where it should be probably within the next month, and I would think that would equate to more MPG, but it also is almost hard for me to believe getting better than what I am getting now. Any thoughts?

 

[ruking]

Probably in your case, the slight heat wave and temp in the mid 50's F. Sea level gives the best mpg readings. Also generally the best is the drier the humidity the better.

The best is to have the timing dead on.

 

[CALL911]

Well the timing is WAY off (on the low side). I guess I'll see what that does.

 

[Bob_Fout]

Spring and fall net the best MPG in most parts of the US. Not so hot to require A/C or impact IATs, not so cold that warm-up times are a major factor.

 

[jnapier]

HUGE Difference for me. Look at the SPIKE here in recent days, then look at the BIG Drop. Temps were upto 70 in the spike, and around 30 in the drop. Same basic driving.

My Fuelly Profile

Jay NaPier

 

[Lightflyer1]

Make sure you know what you are doing when adjusting the timing.

 

[CALL911]

Make sure you know what you are doing when adjusting the timing.

Yeah, a buddy and me have found the info on how to do it. We went in on a scan software to read everything our TDI's computer is showing. I believe we have everything we need to accomplish it correctly, except for time in our busy schedules right now. Hopefully in the next few weeks we'll be able to tackle this.

I am very curious given the very low timing setting on my TDI what kind of MPG change it will make once it is advanced to where it should be. I already thought averaging 52 MPG in the winter was really great.

 

[dieselfuel]

call911,

What is your timing set at now? What is your IQ setting at?

 

[Lightflyer1]

Yeah, a buddy and me have found the info on how to do it. We went in on a scan software to read everything our TDI's computer is showing. I believe we have everything we need to accomplish it correctly, except for time in our busy schedules right now. Hopefully in the next few weeks we'll be able to tackle this.

I am very curious given the very low timing setting on my TDI what kind of MPG change it will make once it is advanced to where it should be. I already thought averaging 52 MPG in the winter was really great.

I am hoping that doesn't include paint or markers of any kind and does include the required lock down tools.

 

[CALL911]

call911,

What is your timing set at now? What is your IQ setting at?

If you are really curious, contact 5SP TDI as he has the laptop we looked everything up on. From what I recall, the timing was so low, it wouldn't even register properly. I forget the exact reading it gave.

I am hoping that doesn't include paint or markers of any kind and does include the required lock down tools.

We got the info to do it properly from this board, and from my discussion to 5SP TDI, I don't recall anything about paint or markers.

 

[Lightflyer1]

excellent!

 

[Peter Cheuk]

I know, it's a gasser, but, my TDI didn't have an on-board trip computer like the GLI does. When I was working evenings I had noticed that I had gotten consistently better mileage driving to work despite there being more traffic at 1 PM than when driving home at 11 PM, though it was a lot cooler driving home. Having switched to mornings, I'm finding that I get better mileage driving home after 3 PM compared to driving to work at 5 AM when the air was cooler. The only thing I can think of is that the cooler air resulted in lower mileage numbers on th MFA. Best mileage achieved was driving with a light foot going to work (30 hilly miles) when I was working the evening shift was 34 MPG. The best driving home mileage I have seen so far, again, driving with a light foot and even doing some hypermiling, was 32 MPG. I know, it's all anecdotal evidence, but, I have noticed this trend and it's fairly consistent.

 

[5SP TDI]

Here is CALL 911's timing chart from VCDS...

 

[CALL911]

Well, BIG thanks to 5SP TDI for helping me last night. We got the timing adjusted back where it should be. I instantly noticed a much better throttle response, and seems to be generally more peppy.

We'll see what the difference is in fuel economy. Honestly, even if it doesn't change, I will have peace of mind its back where it should be, vs where it was.

BTW, 5SP TDI, I was able to get a couple extra gallons of fuel after that other mod we did last night. Amazing!

 

[NewTdi]

Wow,
The timing was really retarded. I am guessing 3-5mlpg improvement at least now that your timing is right on.

 

[CALL911]

Wow,
The timing was really retarded. I am guessing 3-5mlpg improvement at least now that your timing is right on.

Given that I got 52 MPG on average, and have gotten a best of 58, an additional 3-5 MPG would be amazing!

Give me a few weeks, and I'll post up the difference in MPG (if any).

 

[dieselfuel]

So, where on the graph is it set now? 65?

 

[CALL911]

So, where on the graph is it set now? 65?

It was right in that 65 to 70 range.

 

[CALL911]

Well, filled up yesterday, and got 53 MPG. I am guessing this will fit into what I average, which increase 1 MPG over what I got previously. Granted the temps have been warmer now than before (averaged 75 F, comapared to my best at 58 MPG at 60 F).

 

[2002MK4]

Probably in your case, the slight heat wave and temp in the mid 50's F. Sea level gives the best mpg readings. Also generally the best is the drier the humidity the better.

The best is to have the timing dead on.

How much of a difference can timing make?

 

[CALL911]

How much of a difference can timing make?

In my case, even the big change in timing only made a small difference.