Why does my heavy-duty truck's battery keep dying overnight?
A heavy-duty truck battery that dies overnight usually has a parasitic draw from a stuck relay, faulty alternator diode, or an accessory…
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Heavy-Duty Vehicles & Fleet
Practical, step-by-step fixes for heavy-duty vehicles & fleet problems — 62 published so far.
Why is my 2018 Freightliner Cascadia getting 2 mpg worse than last month
A sudden 2 mpg drop in a 2018 Freightliner Cascadia usually means a clogged air filter, leaking boost tubes, failing injectors, or…
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Why is my 2020 Freightliner Cascadia getting 1 mpg worse than last month?
A sudden 1 mpg drop in a 2020 Freightliner Cascadia usually means a clogged DPF filter, leaking fuel injectors, low tire pressure,…
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Why is my 2020 Kenworth T680 burning 15% more fuel than spec
A 2020 Kenworth T680 burning 15% over spec usually points to a clogged DPF, faulty injector, low tire pressure, or excessive idling…
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Why is my 2020 Peterbilt 579 suddenly using 15% more diesel fuel?
A sudden 15% fuel economy drop in a 2020 Peterbilt 579 usually stems from a clogged air filter, faulty fuel injectors, low…
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Why is my 2021 Freightliner Cascadia suddenly getting 4.5 mpg instead of 6.5 mpg
A sudden drop from 6.5 to 4.5 mpg usually means a clogged DPF forcing frequent regens, a leaking charge-air cooler hose, bad…
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Why is my 2021 Kenworth T680 suddenly getting 6 mpg instead of 7.5 mpg?
A sudden drop from 7.5 to 6 mpg on a 2021 Kenworth T680 usually means a clogged air filter, low tire pressure,…
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Why is my 2022 Freightliner Cascadia getting 1.5 mpg worse than last month?
A sudden 1.5 mpg drop in a 2022 Freightliner Cascadia usually means a clogged diesel particulate filter, failing fuel injectors, low tire…
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Why is my 2022 Peterbilt 579 burning 15% more fuel since the last dealer visit
A sudden 15% fuel economy drop after dealer service usually means the ECM was reflashed with a calibration that changed injection timing…
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why is my diesel truck burning more fuel than usual all of a sudden?
A sudden jump in diesel fuel use usually comes from something simple: underinflated tires, a clogged air filter, a dragging brake, or…
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Why is my diesel truck burning more fuel than usual?
A diesel truck burning excess fuel usually means a clogged air filter, faulty injectors, low tire pressure, or a malfunctioning turbocharger —…
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Why is my diesel truck getting 2 MPG worse than last month
A sudden 2 MPG drop usually means a clogged fuel filter, failing injectors, low tire pressure, or a stuck EGR valve —…
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