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• The oil fill on the 6.9/7.3 IDI is located near the front, center of the engine (red arrow in image) at the top of the injection pump gear cover. If the cap's rubber seal is worn, rotted, and/or deteriorating, replace it; it is an inexpensive item and you do not want chunks of rubber dropping into the front cover.
• Place a drain pan beneath the engine oil pan and remove the drain plug, which should require a 3/4" wrench. Once the oil has drained completely, clean and replace the plug. Re-installation of the plug should be done by hand first to ensure cross threading does not occur. Snug with a wrench, but do not overtighten.
• The oil filter is located on the driver's side of the engine, near the end of the oil cooler and to the side of the oil pan. Place your oil drain pan under the filter and remove it. If the previous filter was not over tightened, you should be able to free it without a filter wrench. If you can't loosen it, you'll need an oil filter wrench or large set of channel locks (fortunately, there is plenty of workspace).
• Double check that the old oil filter gasket did not stick to the oil filter mount. Clean the mounting surface with a clean rag.
• You will need 10 quarts of fresh engine oil and a new engine oil filter. We are using Amsoil's full synthetic 15W-40 diesel oil. If you have not converted to a full synthetic, the level of protection greatly exceeds that of conventional "dino" engine oils, and the oil is less susceptible to thermal breakdown and shear. A conventional (petroleum based) oil is perfectly adequate for the IDI, but we believe synthetic oil is well worth the additional cost.
• Stay away from cheap or generic brand oil filters (i.e. Fram). We only use Motorcraft brand oil filters on any Ford vehicle that we service, and recommend you do the same. The Ford part number is FL-784; a larger FL-1995 designed for the 1st generation 7.3L Power Stroke will also fit, but you will need to add 1 quart of oil to the total capacity (total becomes 11 quarts).
• You may fill the new oil filter with fresh engine oil before installing it. This step is optional, but provides an extra layer of protection during startup following an oil change. Lubricate the o-ring of the new oil filter with fresh engine oil, and then install it (important step, the filter will not seal properly without a coat of oil on the black seal/gasket). Hand tighten the filter only, do not use a wrench.
• With the drain plug and new oil filter installed, fill the engine with fresh motor oil through the oil fill. Use a funnel to minimize spilling. Reinstall the oil fill cap and start the engine, making sure that engine oil pressure rises to normal within a few seconds. With the engine running, check for leaks. With the engine off and cool, check the oil level via the dipstick (passenger side) to verify that the proper amount has been added to the crankcase.