US oil inventory preview: five terms that explain what traders will be watchingUS crude stockpiles are expected to have risen last week while fuel inventories fell, a Reuters poll showed. Early industry data, however, points the other way on crude. Here's what's expected, and what the key terms in the weekly reports actually mean.What analysts expectAnalysts polled by Reuters expect crude inventories to have risen by close to 2 million barrels in the week to 2 October, roughly in line with the five-year average for the time of year. Gasoline stocks are seen falling by a similar amount and distillate stocks by about 2 million barrels. Refinery utilisation is expected to have slipped slightly from about 92.5% of capacity.The previous week's official data surprised the market. Crude stocks rose by about 900,000 barrels to around 427 million, when analysts had expected a small draw.What the API showedThe American Petroleum Institute's figures, released after Tuesday's settlement, pointed in a different direction. According to market sources, the API reported a crude draw of about 2 million barrels, against expectations for a build. Gasoline stocks fell by about 1.4 million barrels, while distillates rose by roughly 460,000 barrels.The API data comes from a voluntary industry survey and often differs from the government's figures. The official Energy Information Administration report is due on Wednesday at 10:30 am ET (14:30 GMT) and is the market's benchmark.The terms explainedCrude inventories. This is the volume of unrefined oil held in commercial storage across the US, at tank farms, terminals and refineries. It excludes the government's Strategic Petroleum Reserve, which is reported separately. A rise is called a "build" and suggests supply is outpacing what refiners need. A fall is a "draw" and suggests the market is tightening.Gasoline stocks. Gasoline is the largest single product made from US crude, so stock levels are a direct read on consumer fuel demand. Falling gasoline stocks with refineries running steadily usually point to solid demand at the pump.Distillates. This covers diesel and heating oil, the fuels behind trucking, farming, industry and home heating. Distillates are especially closely watched at the moment because diesel prices are at record highs. A draw would suggest the shortage is not yet easing, while an unexpected build could offer some relief.Refinery utilisation and refinery runs. Refinery runs are the amount of crude refineries actually process each day. Utilisation expresses those runs as a share of total operating capacity. At around 92%, US refiners are running hard. A dip often reflects seasonal maintenance, which typically picks up in autumn. Utilisation links the crude and product numbers: when refiners run less, they buy less crude, which tends to push crude stocks up and product stocks down. That is the pattern analysts expect this week.Builds, draws and surprises. Markets react less to the absolute size of a build or draw than to the gap against forecasts. A draw when a build was expected, as in the API data, is typically supportive for prices. A smaller-than-expected build can be too.What to watchThe key question for Wednesday is whether the EIA confirms the API's crude draw or the analysts' expected build. For product markets, the distillate number matters most: with diesel at record levels and emergency stock releases being organised, any sign that inventories are rebuilding would be closely scrutinised. This article was written by Eamonn Sheridan at investinglive.com.