I don't ever recall an actual instance where planes were literally grounded due to fuel shortages. Although there may have been incidental cases where during retreat soldiers would leave their equipment behind, I haven't seen a case where they just couldn't get into the air (or on the ground if only because Japan didn't field a very large tank unit).

That said, the fuel shortage would cause difficult circumstances for the Imperial Japanese Navy due to the difficult of fielding ships during an oil shortage. Ostensibly the fact that fuel was so limited for ships limited their operational capacity forcing the Japanese to be on the defensive or to use the Carrier and Battleship fleet only when necessary.

With that said, however the amount of fuel wasn't the only problem. Quality of fuel also haunted the Japanese military especially the aviation forces. But before I go into a long digression about how aviation fuel is a higher octane and lower octane can degrade performance of engines, let me answer your primary concern about fuel. Then I'll try to explain how fuel shortages weren't the only crippling concern.

In terms of fuel, Japan was actually surprisingly adept at budgeting for fuel. The air force was more often than not crippled by a dire lack of quality control due to a raw materials shortage than a lack of fuel. Although they were on a budget in terms of what missions could be accomplished, Japan's fuel shortage wasn't crippling enough to ground their air forces until late 1944 and 1945 due to US strategic bombing on refineries and transport routes. Even then, Japan's air forces (which I'll focus on since it's my area of knowledge) weren't grounded much if only because it had ironically shrunk so much compared to 1941-1943.

Now onto the fun part!

Aircraft Engines almost always prefer higher octane fuel. The reason being that higher octane fuel can withstand more compression and in turn allows for higher performance and much higher compression ratios. In relation to Japan, the fuel shortages meant that high quality, very refined fuel was rather hard to come by. In turn low quality fuel would affect engine performance (at times noticeably depending on the engine design and the altitude or use of a supercharger) and reliability. In turn, lower fuel quality would in the long run, increase chances of engine failures of malfunctions and lowering service hours of engines.

However, fuel was not the only issue. The lack of precious metals like bauxite, copper, nickel, vanadium, would make manufacturing an utter nightmare for Japanese aviation. Couple it with a lack of raw materials like iron, coal, and aluminium and build quality for airplanes drops dramatically. The inability to make high quality steel with nickel in large amounts for example essentially crippled Japan's capacity to make precise and powerful equipment.

One of the most notable and prolific engines; the Nakajima Homare (Ha-45) for example suffered heavily from the lack of high quality materials for manufacturing. Despite the design being a rather powerful 18-cylinder radial capable of approximately 1900HP, manufacturing difficulties and the lack of quality materials would cut down the HP production to around 1400 or less depending on the circumstance and the construction of the engine. Likewise the Kawasaki Ha-40, a German Diamler-Benz 601 Inline V-12 copy, suffered as well from reliability problems due to the low quality metals used in the engine. Specifically the driveshafts of the Ha-40s would fail alarmingly quick having a service life of 60-70 hours at best. For comparison the early versions of the Jumo 004 jet engine with improper training usually had a service life of 40-50 hours before failure.

Engines though weren't the only thing affected by the shortage of precious metals. The lack of high quality metals would also affect armament manufacturing as well. Notably in aviation the Ho-5 20mm cannon, a upscaled Type 1 (which was an adapted Browning .50 made to fit the 12.7x81mm SR round) suffered from heavy unreliability due to the materials shortage. Interestingly, the Ho-5 had to be underloaded to ease the stress of the gun to prevent failures in order to compensate for low quality manufacturing.

Long story short, I think it suffices to say that while fuel was a concern, the most noticeable shortage during wartime would be the raw materials shortage that Japan was under. Although Japanese industries managed to expand and outproduce itself before the war, the input or raw resources to be used dwindled quicker and quicker resulting in low quality manufacturing. So if there was anything that grounded tanks or planes, it surprisingly was less the fuel shortage and more the insufficient quality of manufacturing.

1. Williams, A.G., and Gustin, E. 2003. Flying Guns: The Development of Aircraft Guns, Ammunition, and Installations 1933-45. ISBN 978-1-84037-227-4.

2. Japanese Aircraft of the Pacific War, Rene J. Francillion ISBN: 978-0870213137.

Tameichi Hara noted that during the initial briefing for the Pearl Harbor attack, the admirals talked about how Japan was likely to run out of resources for her warfighting capability within a year. Scrap iron, oil, rubber-virtually everything needed for a modern war machine. It was so bad that for a time the Japanese navy's doctrine forbid ships from providing amphibious support to conserve ammunition, and during training torpedoes would be intentionally misfired and collected so as not to waste the torpedo.

The Japanese, by their capture of the Dutch East Indies, were able to temporarily provide a flow of oil back to the Home Islands. However, this flow did not allow Japan to build up enough of an adequate supply, partly due to US submarine activity but also simply because of the poor state of Japanese commercial shipping-namely, there weren't enough ships. As a result, while the navy was able to conduct combat operations and notably wasted a lot of oil on silly operations chasing ghosts, at other times they were extremely miserly.

For instance, despite having the Yamato and Nagato class battleships available for Guadalcanal, their obscene fuel consumption caused them to sit on their hands while smaller, more fuel efficient but weaker ships were sent to contest the waters. One of my favorite websites has an article illustrating precisely how bad the fuel situation was for the Japanese navy. As a result, instead of fighting mano-a-mano against the US battleships in Guadalcanal, Yamato was being a hotel for naval officers in Truk lagoon for the entire duration. Had Yamato been the battleship present during the second Naval Battle of Guadalcanal instead of Kirishima, it is fairly likely that the Japanese could have triumphed. However, doing so would expose her to air attack as well as consume an ungodly amount of fuel-especially in combat operations-which would have been a sizable chunk of the IJN's fuel supply.

At some points, the situation was so bad that every drop of oil was scraped from the bottom. Literally in some cases, like for instance, when the battleship Mutsu suddenly exploded in harbor, divers were sent to retrieve the fuel left in her tanks.

The battle for Leyte, too, was caused by the oil problem. The Japanese were forced to throw all their remaining assets at Leyte Gulf simply because the fall of the Philippines would effectively prevent any further oil shipments from getting back to Japan, thus grounding the Japanese Navy. And indeed it did-aside from a suicidal sortie by Yamato in April 1945, all the remaining Japanese capital ships were turned into floating AA platforms and remained in harbor for the rest of the war. There, they were sitting ducks for US air raids-like the Raid on Kure.

...before Pearl Harbor. but how bad was it really?

Well before their attack on Pearl Harbor, Japan struggled to achieve and maintain petroleum reserves for use by their armed forces and civilian industries. Prior to start of World War II, nearly all of Japan's petroleum was imported, primarily from the United States who supplied almost 80% of their petroleum needs. For specialized petroleum distillates like gasoline and aviation fuel, the percentages were 90% or more.

Thoughout the 1920 and 1930's as their national policy of economic self-sufficiency and independence unfolded, Japan made efforts to stockpile petroleum reserves but their military campaign in China was a continuous drain on their stockpiling efforts. In 1934 and again in 1938 and in order to support of the conflict in China, reductions in petroleum quotas were levied against civilian industries. Shipping had to absorb almost a 40% reduction in quota and the fishing fleet was forced to rely on wind and sail power to supply food.

Michael A. Barnhart, Japan Prepares for Total War: The Search for Economic Security. 1919-1941

David Lawrence Hanley Japan Aircraft Development 1922-1945.