555/600 mileage comparison

[ACF]

I know this is not what most people have been writing. But I just did a combination hwy/city mpg test based on the trusted hand calculated method. With allot of city driving and some hwy use I just got 16mpg in 479 miles of driving out of my 05 QC 4x4 48RE Larime SB SRW. The exact same truck in a 04 555 version that I used to own got a best of about 15. 4 mpg with a little less city driving... or less traffic I should say. I am very happy with the mpg on the 610 so far. I have yet to match the 555 while towing however as it was new when I towed with it... still is at just over 3k. My overhead still reads about 2 mpg too high however.

 

[RMalone]

I tend to be in the 16. 5 to 17 mpg on no. 2 diesel I have a 04. 5 325/600. My driving sounds similar to acf. Funny thing is my overhead consistenly reads 1. 5 to 2. 0 low compared to hand calced, thats with no. 2 diesel. With conditioned (winter blend) diesel my overhead is only about . 5mpg lower than hand calc. Im sure someone knows why, by the way why cant they either get the overhead right or just leave out altogether? In trucks that have the overhead milage calc I always try to use it, however I never seem to miss it when the truck doesnt have one.

 

[Gary - K7GLD]

" Im sure someone knows why, by the way why cant they either get the overhead right or just leave out altogether?"



WELL, along THOSE lines, I suppose they could ALSO leave off the oil pressure guage as well, since guys who have installed mechanical guages invariably report the stockers are WAY off... :-laf :-laf



And then there's that inaccurate voltage meter - and has anyone REALLY checked the water temp guage for accuracy?



These ain't 4-wheeled laboratory instruments - and some of the readouts are more for the sake of casual monitoring and comparisons, rather than precise measuring tools!



Work for most of us! :-laf

 

[jwduke]

My overhead reads about 1. 5 mpg low. I'm getting 16. 5 & it reads 15.

 

[CumminsBu]

555= 17 city 20 hwy best was 22 hwy. All hand calc.

 

[BHolm]

I get 2-3mpg better with the 555's over my 610. Where I really noticed the difference was at speeds over 70-75. The 555's seems to get much better milage than the 610. I can get 18-19 at ~80-85mph with a 555 QC srw and get 14-15 with the 610 on the same trip.

 

[ACF]

I will get back to you all once I get to go through several tank fulls in a variety of conditions. Like I said right now it looks as if she is at least as good at if not better than the 555 in my day to day driving... ... . time will tell as this was just based on one full tank of diesel. I have yet to get even close to the 555 while towing my insignificant (for a Cummins) 5300 trailer. The best so far has been 12. 1 vs 14. 1 on a the hwy in the mountains. But then again the truck was brand new and I have only towed once. Once again time will tell. I have only two complaints with the truck... . both very minor. The dome light blew the first time I turned in on with the swith and as mentioned above the computer is way off. Other than that it is a better truck than my 555 as it shifts smoother, has a superior TOW/HAUL (although still could use a little upgrading) and is much more quiet and has less NVH.

 

[jcarey]

Never had the 555, but our 04. 5 has an overall mpg average of 18. 02 since purchase.



Dates run from 5/29/2004 thorugh 2/12/2005 (haven't updated for the most recent tankful yet).



Lowest mileage was 14. 82 mpg (12/11/2004). I think that was due to clogging injectors. Had white smoke rough idle at cold startup. Had TSB and started puttting Redline in. After a couple of tankfuls, mileage was back to normal based on the 1/16/2005 fill-up - 18. 13 mpg on winter fuel.



Highest mileage was 20. 05 mpg on 7/18/2004, 90% highway.



Source: XCel spreadsheet.

 

[BHolm]

Conditions play such a big part in milage, I think it is hard to really compare. When I see east coast guys with high highway milage I take into consideration that the speed limits are considerably lower there than out west. Keeping the 3rd gen trucks under 75mph really makes a big difference in milage. Most states in my part of the country have 75mph limits which means traffic flows at 80+ and when I have a road trip to make I regularly run 85-90mph. No way to get 18mpg out of a 600 at those speeds.