Diesel Engine Break-In Myth?

dubStrom

Veteran Member
Joined
Aug 6, 2007
Location
Kansas City Missouri
TDI
2003 A4 Jetta (sold), 2010 JSW (sold), 2013 Passat 6MT traded for 2014 JSW with 6MT-TOTALED in November 2016, 2003 ALH 5MT conversion (sold), wheezing 2015 GSW/DSG and a new 2021 Tacoma Access Cab 4x4 p'up
broken in during Summer Heat

I know cooling systems are supposed to keep the block relatively constant temp, but peripherals get heated by/or cooled by ambient temp as well. I bought my JSW in late May. It was a HOT Summer. So it run up to temp FAST while I drove the first 4000-6000 miles. Now it is Fall, and even before it was cold I noticed a distinct improvement and consistency in mileage.

So this brings up two questions... how much of the improvement is due to break-in (I am at 10k now). And second question... Do you get better mileage in winter, or when it is colder anyway? Efficiency in a diesel has something to do with heat differential (even more than gasser), doesn't it?
 

TornadoRed

Top Post Dawg
Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Golf GLS 5-spd, indigo blue; 2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (retired); 2003 Jetta TDI wagon, Candy White (sold)
I know cooling systems are supposed to keep the block relatively constant temp, but peripherals get heated by/or cooled by ambient temp as well. I bought my JSW in late May. It was a HOT Summer. So it run up to temp FAST while I drove the first 4000-6000 miles. Now it is Fall, and even before it was cold I noticed a distinct improvement and consistency in mileage.
So this brings up two questions... how much of the improvement is due to break-in (I am at 10k now). And second question... Do you get better mileage in winter, or when it is colder anyway? Efficiency in a diesel has something to do with heat differential (even more than gasser), doesn't it?
Some of the improvement is due to break-in. And some is due to cooler air temperatures, making the intercooler more efficient. However, in a few weeks you'll be filling up with winterized fuel; your fuel economy will decrease because of longer warmup times and because winterized fuel has a lower BTU content.
 

NewTdi

Top Post Dawg
Joined
Jan 15, 2004
Location
NorCal
TDI
2003 Bora, Reflex Silver
How much crap do you have in an E class to get it to 5800lbs
He loaded it with bricks and concrete for the break-in procedure to make sure it was working under load! :D
That is one heavy car!
I am trying to talk the wife into a BMW wagon diesel for our next car, but she does not like wagons at all, so she's saying a Taureg 6 cyl is best for us!
 
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