Just put 8K mi on new 02 Cummins. Getting 10 to 13 mpg. Talked to 2 dealers who said it takes 8 to 10K mi to break-in before maleage improves. Can anyone tell me if this is true or do I have another problem? My old 92 got about 18 mpg.

 

My Y2K got as good new as it did later, around 19 to 20 on the frwy. empty.

 

I have 20k on mine now, and mileage is the same as when new- around 18-19 on the highway, empty.

 

Mine was 12-14 on the highway new, but after around 15K, and warm weather, it went up to around 21. You have another thing probably working against you at the moment, and that's blended fuel. I say probably because you don't have you location listed. If you live in a cold climate at the moment, things will start to get better by mid-April or so. Truth be known, if you do a lot of town driving, traffic lights, etc., your mileage is going to stink, and you're probably not going to see better than 12-16.

 

So many factors can affect fuel mileage, that it can be difficult to pin down whether you have a problem, or not.
Type of travel, driving style, trans type, gear ratio, tire size, time of year, etc. are all factors.

In my 13k so far I have seen a little improvement. Nowhere near as drastic as with my '90. You could almost watch it increase by the tankfull.

I have seen a low of 14, (short/medium trips towing light loads), and a hi so far of 18.5, (medium, easy trips, empty). No long road trips, and the taller tires just went on, as did the synthetic in diffs. Syn in engine @ 10k. I expect to get just a bit better. Must be time to add fuel

My impression is that your numbers are on the low side, and I might start looking for cause, or contributing factors.
Majority of your break-in has been acheived.
A combination of the items listed in first paragraph could bring about these numbers, but it is my opinion that most all would have to line up against you to explain your current fuel economy, or lack thereof.

 

Last fill up I got 17.8 MPG. 70% city, 30% hwy. Overhead said 18.8 MPG. 56,000 miles on it.<br><br>Mike

 

Mine is the first generation 24 valve. 98 1/2.<br><br>Ive had mine since it had 5,000 miles on it. Today, it has just a tick over 123,000 miles. I still get 20 mpg on the highway, empty.

 

When I am working a short distance from home, my mileage is down around 13mpg. I am also loaded with 1200 lbs of tools.

 

I get 22 to 24 on the highway, 19 arround town and 15 to 18 towing.

 

Mine has 17,000 and I still only get 10-14mpg. The average is 11.<br> Scooter ??? ???

 

Averaged around 15.5 as new. Now have 14,000 and put in an EZ. I got 17.8 on my last tank.

 

I'm getting 21-24 highway @ 60-70 mph, Maybe it's the AMSOIL ;D

 

I get 7 to 11 loaded,and 17 to 18 emty. Still using Rotella with no mods. 112,000 on it now. not happy.

 

I GET 19-21 ON H-WAY EMPTY@75-80. WITH CAMPER &amp; BOAT 13.5@75-80 I HAVE A VERY SMOOOOOTH DRIVING STYLE!

 

My 02 has just over 8K on it and I'm getting between 19 &amp; 20 mpg on the hwy. with a HO, 6speed, 354 LS, empty.