question for the long hood people who actually track fuel and don't just guess.
i run a 2019 389, 131 hood, X15 at 500, 13 speed, pulling a 53 foot Utility reefer. mostly Des Moines to Chicago and Omaha, some Denver in the winter. average on the last 40k miles is 5.6 on the dash and 5.4 by the pump receipts. my brother in law runs a 2022 579 on the same lanes at about the same weight and gets 7.1.
on 120k miles a year at 3.70 diesel that works out to close to 20 grand a year between his truck and mine. i knew the hood cost money but seeing it on paper stung a little. what are you guys getting, and did anything you changed actually move it?
5.4 real on a reefer behind a 131 hood is an honest number, nothing is wrong with your truck. my last 379 had a C15 and 3.36 gears and did 5.8 on a dry van at 65, and 5.0 at 72. speed was always the biggest lever for me, bigger than anything i bolted on. every mile an hour past about 62 cost me close to a tenth.
the aero trucks win because the air goes around them and the engine lives at 1,150 rpm all day. you don't buy a 389 to beat a 579 on fuel. you buy it because you'll keep it fifteen years and it'll still bring money when you sell it.
flatbed side. 2020 W900L, X15 at 565, 18 speed, 3.55s, pulling a 48 foot Fontaine spread axle. 5.2 average and a lot of that is loaded heavy out to the oil patch west of Williston.
nothing moved my number like tires. went from a lug drive to a closed shoulder drive tire and picked up about a quarter of a mile per gallon. lost some bite on snowy on ramps in january though, you pay for it somewhere.
shop side of it. before you chase mpg with parts, pull the ECM trip report and look at idle percent. i see long hood owner-ops at 25 to 35 percent idle all the time. an X15 at high idle in the lot burns close to a gallon an hour. a reefer guy sleeping in the truck in july can burn 8 or 10 gallons a night keeping the bunk cool. a battery AC unit pays for itself faster than any bumper swap.
and check that the fan hub isn't stuck engaged. seen a few where a bad solenoid kept the fan on all the time, that can be half a mile per gallon on a hot day and you'd never hear it over the stacks.
walt called it. idle was 29 percent on the trip report. the reefer unit has its own engine but i was idling the truck for bunk AC most nights in august. got a quote from a shop in Ankeny for a battery AC install, 7,400 installed. at a gallon an hour, figure a year and a half to pay it off.
also went back through the receipts by lane. the Denver runs average 4.9 because of the long pull up I-76 into a headwind, that one isn't the truck's fault.
team numbers since nobody posted any yet. we run a 2021 389 with the big sleeper, X15, 18 speed, dedicated dry van Eau Claire to Fargo and back with a Chicago leg twice a week. 6.1 average. cruise is set at 64 because my co-driver lost that argument in 2023 and hasn't won it back.
the truck almost never idles since one of us is always driving, which i think is most of the difference from reefer's number. if anyone's specing one new, the options pages on peterbilt.com list the tank and sleeper choices, and those change your empty weight more than people expect.
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