The LF BROS is the best heater of the four and it is not particularly close. It
raised the 800 sq ft shop 9.2°F in thirty minutes against 7.3°F and 7.1°F for
the HCALORY and VEVOR and 4.3°F for the SILVEL, delivered the hottest air at
326°F and the fastest at 41 mph, ran clean with no visible exhaust smoke at any
point, and covered 9 hours 16 minutes on a 5.5 quart tank on the highest heat
setting — a quart of diesel buys close to two hours of heat. It does all this
on a 5 kW rating while the three units it beat are all sold as 8 kW, which is
the clearest possible warning against buying on the number on the box. The
reservation is price: at $250 it costs more than twice the cheapest unit for a
performance gap that is real but not proportional.
For value the VEVOR at $118 is the pick. It landed within 0.2°F of the $200
HCALORY on shop temperature rise, burns cleanly with essentially no visible
smoke, has the simplest one-button start of the group, adds Bluetooth app
control, and is the most economical on electricity at 44 W running and 10 W on
low. The HCALORY earns its extra money on kit and comfort rather than heat — it
is the quietest on the highest fan speed at 69.4 dB, and it is the only one of
the first three that includes a 110V AC-to-DC power supply, which is what you
actually need to run a heater off a wall outlet or a generator. Anyone buying
the SILVEL or the VEVOR should budget for that converter and a cigarette-lighter
lead on top of the purchase price. The SILVEL is a working heater at $95 and
the quietest of the four on its low setting, but it is the smokiest during
warm-up and it finished last on the measurement that counts.
Three cautions apply to all of them. Size the power supply for the start-up
surge and not the running figure: a 100 W supply could not hold voltage through
a warm-up, while 44 W to 54 W is all any of these needs once lit. Vent the
exhaust outside without exception — this is a combustion appliance and the
testing was done in a well-ventilated shop with the flue run outdoors. And on
alternative fuels, vegetable oil works: one cup ran the SILVEL for about 35
minutes, burning clean enough that the combustible-gas meter found nothing, and
a half-and-half blend of used motor oil and diesel ran roughly 50 minutes at
under 100 parts per million. Straight used motor oil does not work — the heater
struggled to ignite it, the meter climbed to around 1,000 parts per million, and
the unit shut itself down on a fuel fault. Either alternative fuel will leave
carbon deposits in the combustion chamber, so they belong in a genuine emergency
rather than in normal use. The upright units, the VEVOR and HCALORY, carry one
more caveat: they tip over more easily than a flat-lying heater, and their fuel
pickup sits on the side of the tank rather than the bottom, so the last of the
fuel stays put.