Just some notes on Haighus's massive guesstimation post:
Imperial Guard vehicles seem to run on anything, so their adaptability is good, but their efficiency is hard to predict. On the whole, it seems Imperial vehicles are much more efficient than modern ones, in part perhaps due to promethium. I would say fuel needs are no more than they are for the modern armoured division, and quite possibly less.
If there is one thing i would object to it is this. I came to a different conclusion. I put the standard fighting vehicles under the microscope from a realistic perspective in my project
: (Most descriptive/investigative stuff is in the log on warseer
If we use regular fuel as input, Imperial Guard vehicles would be only as good as WW2 ground vehicles. The power the engines produce for their given size is comparable to WW2 vehicles - which almost all used naturally aspirated engines
. Example - Leman Russ Engine Phaeton pattern propelling a ~60ton vehicle 35kph. Engine room is in size comparable to a WW2 heavy tanks (e.g. Tigers). If the naming scheme of the engine is any indication there exist LR
patterns with higher engine output (Mars Alpha Pattern Hulls) that use better engines - most likely charged versions. Supercharger (~1950/60 tech in ground AFV) or Turbocharger (~1970/1980 tech in ground AFV) can significantly increase power output for the same engine.
For fuel consumption consider that their standard AFV are really heavy. Leman Russ are heavy tanks for todays standard, and that's pretty much the only Battle Tank they use. Chimera and anything with that chassis is also around 40 tons, which is pretty heavy as well.
Empire of mankind is very fond of tracked vehicle designs in general. Almost all AFV are tracked. Many non-AFV are also tracked or track-like. So their percentage is higher in the motorized and logistical chain than in modern army.
Tracks increase fuel consumption since tracks have much higher resistance to movement and therefore higher fuel consumption than wheeled vehicles.
Just a nice example for the whole tracked vs wheeled logistical thing: consider that Soviets made giant Offroad Tank transporters (MAZ 535 and 537). It pulls a trailer (probably >10t) with their MBT on it (40-45t) on it, and it's own weight(22t). The Truck has the same engine as the tank it pulls (though less optimized), and they still considered this a valid strategy compared to the tank driving around on it's own.
Soldiers need more energy than people not fighting, so they have a bit more in terms of food than civilians (often around 4,000 calories per day). Note this is for the modern regiment- WWII regiments seemed to eat 35 tons per division, rather than 25. I suspect this is primarily due to improvements in packaging- much WWII food was canned, rather than vacuum packed in plastic, so that would increase the weight a lot. 35 tons vs 25 tons is a fairly huge increase though! I am going to use the lower, modern values.
The difference between modern and WW2 soldier is that there was a lot more physical work required back then due to lower percentage of motorized/mechanized forces and efficient equipment. Remember in WW1 german soldiers walked from german border to the frontlines in France at beginning of the war. Modern field systems are often self driven or at least have motorized tractors. In WW1 and WW2 a lot of stuff was simply carried, manhandled or pulled and carried by horses. Also equipment was much bulkier and much less weight optimized. No plastics, no advanced engineering for making everything only as heavy as it actually needs to be. Imagine pushing those 75mm and 88mm anti tank guns on steel carriage through russian mud all day, while wearing a backpack that has a steel skeleton that already weighs 6+kg on it's own. Imperial Gear is very much inspired by WW1 to Korean war (at least the old units - Steel legion, Cadians, valhallans, ... ). Just look at the vox caster. Soldiers in WW2 didnt have body armor back then. Imperial Guard do, esp. Cadians. So from physical demands i would expect an increase compared to modern stuff - because more personal carry weight than WW2 and about same material optimization degree.
As a sidenote (or key point depending on ground situation
One thing unmentioned on a planet like this is drinking water... Very significant for logistics as well, because it has a big impact on infantry physical and mental performance, and they can't survive without it (as opposed to fuel, where units just become immobilized when it's lacking) It may be processed from local water wherever available - but to anywhere else it still needs to be transported around. And if the processing plants are disabled or supplies are cut off ... things look grim.
Another sidenote: Having to wear respirators, or worse, having to wear special protective clothing all day is extremely exhausting. The amount of sweating under even light physical activity in such sealed suits even under normal conditions is surreal. Now imagine full day full on activity in hot and dry conditions. So if it's really necessary to wear such clothing on armageddon most of the time then this will drive up food and water consumption considerably.