Depreciation is computed using the straight-line method over management's estimated useful lives of the related assets, which are as follows:
Years
Building and building improvements
15-40
Refinery machinery and equipment
5-40
Pipelines and terminals
10-40
Refinery turnaround costs
4-6
Automobiles
3-10
Computer equipment and software
3-10
Furniture and fixtures
5-15
Property, plant and equipment, at cost, consist of the following (in millions):
December 31,
20252024
Land$45.9 $41.2 
Building and building improvements57.7 53.4 
Refinery machinery and equipment2,479.9 2,349.1 
Pipelines and terminals1,937.8 1,454.1 
Refinery turnaround costs652.7 526.6 
Other equipment159.8 187.6 
Construction in progress253.1 336.4 
$5,586.9 $4,948.4 
Less: accumulated depreciation(2,314.4)(2,008.4)
$3,272.5 $2,940.0 

About PP&E Disclosures

The PP&E disclosure details a company's physical asset base — land, buildings, machinery, and equipment — along with the depreciation methods and useful life assumptions that determine how these costs flow through the income statement. Capitalization policy thresholds reveal management's judgment on the boundary between expense and asset, directly affecting both reported earnings and asset values.

Key signals: changes in estimated useful lives or depreciation methods can materially shift reported earnings without any operational change. Compare capital expenditures against depreciation expense — when capex consistently trails depreciation, the asset base may be aging and underinvested. Watch for large asset impairments or write-downs that signal overvalued carrying amounts. Asset retirement obligations reveal future environmental or decommissioning costs that are often underappreciated. Compare PP&E intensity (PP&E-to-revenue) against industry peers to assess capital efficiency and competitive positioning.