TRANSMISSION AR 4499612 - Caterpillar

Fuel consumption complaints are related to engine owners expectations. They may often times be related to the engine itself, causes other than the engine, and in some cases the fuel consumption may be normal for the application. Only a good discussion with the owner/operator, as described in the "Owner/Operator Input" section, will give guidance as to a correct repair or to prevent unnecessary repairs.Owner/Operator Input
The following are some of the questions which should be asked before beginning any diagnosis or repair for an engine performance complaint. There Are No Hard And Fast Answers For These Questions. There are many factors that can cause poor fuel mileage or make users believe they are getting fuel-poor-mileage.There are also a variety of customer expectations which are acceptable. The answers to these questions will give you a better understanding and perspective on the complaint and may identify characteristics which will help pinpoint the cause of the complaint quickly.1. Are miles measured accurately? A most common problem in determining mpg is errors in recording the number of miles traveled.A. Is this vehicle hub or cab odometer accurate? The easiest way to check an odometer is to install a hub odometer known to be accurate and for the tire size on the truck. Run the truck over several hundred miles and compare the reading with the original odometer.Odometers may also be checked by comparing them to interstate mile posts or by running over a course of known length - a 50-mile run is required to get a good check.B. Are "book miles" or "driver-paid miles" correct? Another way in which miles for mpg calculations are obtained by a fleet is the use of "book miles" or "driver-paid miles". The use of this system can short mileage accumulation by 10 to 15%; thus, mpg is low by 10 to 15%.C. Is the vehicle used for pick-up and delivery operation? Another problem affecting mileage accumulation in many fleets is the use of linehaul equipment for pickup and delivery operations. In the "book mile" system, the truck rarely gets credit for any miles run in pick-up and delivery.2. Is fuel measurement accurate? There are a number of ways in which fuel measurement can be the source of mpg problems.A. Are fuel pumps calibrated? If fuel tickets come from company-owned fuel pumps, there can be errors because nonrevenue fuel pumps do not have calibration requirements in many states.B. Are road fuel tickets accurate? The only way to verify fuel additions when road fuel tickets are used is a laborious ticket-by-ticket audit ensuring that the correct amount of fuel has been entered for the vehicles in question and that there are no indications of incorrect entries.C. Are tank-full mileage checks correctly done? The big problem in "tank-full" checks is getting the tank filled to the same level before and after the user "checked the mileage". With two 100 gallon tanks, errors of 5 to 10 gallons are very common in topping off tanks because of the way truck tanks