Just ran the numbers on how much DEF a new fleet truck burns through in a year

I was going over maintenance records for a 2023 Freightliner Cascadia we service at the shop, and I swear I had to double check my math. It was using almost 800 gallons of DEF over 120,000 miles. That's like $2,000 a year just in fluid for one truck. Crazy when you think about how much extra that adds to operating costs. Anyone else tracking these numbers close on newer trucks?

3 comments

3 Comments

murphy.linda14d ago

Call the DEF bill a drop in the bucket compared to fuel savings from the emissions system.

jamie_white14d ago

Yeah calling it a "drop in the bucket" makes sense honestly. I saw this article the other day that said modern engines with DEF actually get like 3-5% better fuel economy compared to older EGR-only setups. So the cost of DEF is basically nothing when you factor in the fuel savings over a year of driving.

morganhill14d ago

Respectfully @jamie_white, those fuel economy gains are real in controlled tests but they disappear fast depending on how you drive. Stop and go city driving with lots of idling burns through DEF and can eat into that 3-5% pretty quickly. I run a small fleet of work trucks and the savings only show up on long highway hauls, not around town. The DEF cost might be small but the fuel economy bump is inconsistent at best.