<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Diplomat Don:
PL KIDS.....I don't have a CAT, but have the 400 Cummins in a 36'. I would think that our mileage should be similar. Are you checking your mileage by doing the actual math of gallons into miles and are you averaging at least 3 or 4 tanks. With the large tanks in diesel motor homes, unlevel fuel staions and different delivery speeds it's easy to overfill or under fill them.
You need to do some averaging to get a good figure. My 400 ISL is averaging 8.3. If your doing all of the above and your numbers are accurate, you might have some issues that need correction like a turbo or ECM flash. </div></BLOCKQUOTE>
Re ECM flash - the ECM takes 145,000 miles before one gets an accurate reading because of what is called First Fill Effect
This a graph depicting effect:
This shows it using a 200 gallon tank
I've cut it short but I think one can get the idea.