FPInnovations have a fuel economy guide which is free-for-download from their website.

This concise guide is titled “In forestry operations, fuel economy counts!”. It is aimed at forest machine owners, and attempts to provide information for improved machine fuel consumption. The guide is easy to read and makes good use of diagrams and illustrations. It is divided into the following sections:
 

• The factors that influence fuel consumption.
• It examines the accessories and parts that play important roles in fuel efficiency. These include engine power, the fan, the power train, differential lock, hydraulic systems and hydraulic oil coolers.
• Techniques for improving fuel economy. Lighting, tyres, traction aids, engine idling and other points are discussed.
• Fuel consumption rates of different types of logging machines. The graph provided is particularly interesting.
• Tips for reducing fuel consumption with different logging machines. Tables present the information for different configurations of feller-bunchers, harvesters, skidders, forwarders and delimbers.

Source: http://www.feric.ca/en/index.cfm?objectId=826929A1-F4C2-BD43-C9C7FBD61BAE88FD