Being a big fan of diesel motors and everyone knows they are used best fuel mileage, low end torque for heavy duty applications for big trucks, and heavy dirt moving equipment and a lot if not most armor today uses diesel other then the few GasTurbine engines. So why during WW2 did mainly the Germans, British, US and other powers use gasoline (petrol) motors to power their vehicles? especially the heavy armor late in war such as the tigers, panthers and the other big tank destroyers + the US and UK shermans and others also seemed to run off gasoline. The soviets did seem to have the idea of using diesels lower end torque to power their T-34s, KV's IS heavy tanks. I'm assuming this was majority due to what was available at the time? or just was not much of a thought and the technology wasn't there much as it is today?
Diesel technology wasn't, back then, what it is today. There are several factors in play.
Simple logistics. Most things in the German Army ran on petrol, not diesel. If you put diesel motors in your tanks, you need to start trucking two different types of fuel around and, frankly, the German military was not necessarily the best equipped for trucks to begin with. For this reason the US tried to avoid diesel in its vehicles, the only notable exception being the M10 tank destroyer, and the USMC M4A2, simply because those were the only vehicles which could have been fielded at the time. The Marines traded in their diesel tanks for petrol when they could, and the M10's successor, the M36, was built off M10A1s, with petrol engines. If everything's running on petrol, you can fuel everything from Jeeps and trucks to tanks and halftracks from a single truck. Makes life much simpler.
Diesel engines were more expensive, and actually a little less capable than petrol engines of the time. If you look at this brief discussion starting 9:48, https://www.youtube.com/watch?v=jgcM2uLUrxA , David Fletcher observes that he has found an item in the German archives that the decision was made to go with petrol because they wanted the maximum performance possible, for a duration of five hours. Had the operational requirement been for ten hours, they'd have picked diesel due to the superior endurance, even at a cost of less capability.
Diesel is a tad easier to refine. If you're worried about that sort of thing, or significant operational distances, there is more an argument for using diesel in your WW2 tanks, even at the cost of increased engine cost and logistical difficulties.
The Soviets had very long supply lines, and vast distances to cover. The Japanese and Italians had significant shortages of petroleum capability. So, moving to diesel made sense for them. Everyone else, the petrol engine, at the time, just made more sense. It wasn't until the late 1950s/early 1960s when the switch to diesels for tank engines really started happening amongst the Western powers.