cold_start_in_fargoOPPullingFargo, ND29 posts, joined Nov 2025
truck2018 Sierra 2500HD Denali, L5P Duramax
2018 Sierra 2500HD Denali, L5P, 96,000 miles. minus 14 this morning in Fargo, first real cold of the year, and it will get to minus 25 before christmas like it does every year.
i have always just plugged it in when i get home and unplugged it in the morning. 12, 13 hours a night. my wife looked at the electric bill last january and asked what exactly i was heating out there.
so the honest question. how many hours does a modern diesel actually need on the block heater before it does any good, and when does it stop helping? and is it worth worrying about fuel more than the heater? i run whatever the Cenex by the house sells and i have never gelled, but i also have never driven to Grand Forks at minus 30 either.
owner's manual on gmc.com says to plug it in below 0 F, and that is about all it says.
diesel_shop_marcoHigh hoursFresno, CA71 posts, joined Nov 2025
truck2019 F-250 XL 6.7, service body shop truck
Fresno never sees this, but i spent eight years at a shop in Bozeman before i came home, so i have opinions.
a block heater warms the coolant around the cylinders. it gets most of what it is going to get in three to four hours. after that you are mostly holding temperature against the wind, and you are paying for it all night. look at the wattage stamped on the element or the cord end, most of these trucks are somewhere around 750 to 1,000 watts. at 13 hours a night that adds up exactly how your wife noticed.
get an outdoor rated timer, a heavy one, rated for the full amps. set it to come on three or four hours before you leave. if you leave at different times, there are wifi plugs rated for outdoor use now, just buy one with a real amp rating and not the cheapest one.
fuel is a different problem. the heater does nothing for gelled fuel in the filter or the lines.
mod_tracy_lModeratorCheyenne, WY88 posts, joined Nov 2025
truck2017 F-350 XLT 6.7 Power Stroke, SRW long bed
three hours on a timer in Cheyenne, and i have run that schedule since the state shop days. those plow trucks sat outside all night at minus 20 and the ones on timers started as well as the ones plugged in all night.
fuel. the stations up here switch to winter blend in the fall, a mix of #1 and #2, and in the north the big stations do it well. where people get in trouble is filling up in Denver or Kansas on the way home and then parking at minus 25 with southern fuel in the tank. if you travel, carry a bottle of anti gel and treat at the pump before you fill so it mixes. i also keep a bottle of the emergency stuff, Power Service 911, in the door pocket, because the first gel happens on the shoulder and not in the driveway.
and do not leave a diesel idling in the driveway for 20 minutes to warm it up. it barely warms at idle and it is hard on the aftertreatment.
l5p_in_billingsUp to tempBillings, MT14 posts, joined Nov 2025
truck2020 Silverado 2500HD LTZ, L5P, Allison 10 speed
first winter with my L5P, minus 9 in Billings this morning. to tracy's last point, my dealer said the same thing in different words. long idle in the cold loads the DPF up with soot because the exhaust never gets hot enough to do anything about it, and then you get a regen on a 4 mile drive to work that cannot finish. drive it gently the first few minutes and let it warm under a light load.
one more for fargo. a winter front, the grille cover kind. mine came with the truck and it holds heat in the engine bay noticeably on the highway at minus 10. take it off when you tow anything heavy, though.
cold_start_in_fargoOPPullingFargo, ND29 posts, joined Nov 2025
truck2018 Sierra 2500HD Denali, L5P Duramax
report back. bought a Kill A Watt type meter, the cord pulls 1,010 watts on mine. outdoor timer from the farm store, 15 amp, set for three and a half hours before i leave at 6:40.
minus 18 on sunday morning, coolant temp on the DIC read 61 when i started it, fired right away, heat at the floor in about five minutes. that is the same as 13 hours plugged in, as far as i can tell. that works out to about 3.5 kWh a night instead of 13. i will take it.
fuel i am now treating, a bottle in the truck for any fill outside the Red River Valley.
hotshot_out_of_tulsaUp to tempTulsa, OK21 posts, joined Nov 2025
truck2019 Ram 3500 dually 6.7 Cummins, 40 ft PJ gooseneck
reading this from a truck stop in Salina, Kansas at 4 something in the morning so this thread is timely. fueled in Oklahoma city yesterday afternoon with whatever they had, it hit 2 below overnight, and the truck started fine but had no power on the ramp and the fuel filter warning came on. gelled filter.
bottle of 911 in the filter and in the tank, an hour of waiting, and it cleared. should have treated it at the pump like tracy said. lesson learned for 22 dollars and an hour of sleep i did not get.
