I don't want to get in a thick oil vs thin oil argument. I just wouldn't run 20w-50 unless the engine couldn't maintain 8PSI when hot and idling, as my factory service manual states is the minimum for my LA 318, at 750rpm.<br><br>Before I knew better I let a mechanic buddy convince me I needed 20w-50 as these engines "like it" and the motor was sluggish and developed a lifter tick that disappeared when I went back to 10w-40. I now run Mobil1 0w-40 (under25$ for 5 quarts at wally world) and the lowest PSI I see is 16, at 550 rpm when as hot as I can get the oil. I do have an aftermarket mechanical OP gauge installed, the factory gauge is still operational and only vaguely mimics the Mechanical OP gauge, which responds instantly to changing RPM's. 62 PSI is the oil pump relief valve setting on mine. When the oil is hot, 62 psi is reached at ~2000 rpm. <br>Some state the perfect oil weight for any given condition is the weight which keeps the oil pump from going into bypass until near redline, and still maintains the minimum required PSI at hot idle. Perhaps from a maximum HP/torque perspective this is true but I prefer a little more buffer.<br><br>Do get yourself a factory service manual on E bay motors. Haynes or chilton's guides are jokes in comparison.<br><br><a href="
http://www.ebay.com/sch/6000/i.html...rs_Manuals_Literature&_vxp=mtr&_rdc=2" rel="nofollow" target="_blank">
http://www.ebay.com/sch/6000/i.html...rs_Manuals_Literature&_vxp=mtr&_rdc=2</a><br><br>Lots of old wives tales and misunderstandings abound about oil weights.<br><br>a 5w 30 is a 5 weight oil that had Viscosity Index Improvers so that when at full temperature, it has the same viscosity as a straight 30 weight oil at that same temperature. These viscosity index improvers can break down (shear) over time resulting in a thinner oil at temp. Generally the higher the spread of the numbers the more prone to shearing the oil is.<br><br>VII's have improved many fold over the last 20 years, and all name brand oils are now much much more resistant to shearing. There are many 5w-30s that are thinner on startup(good) and just as thick at 100C as 10w-30's, and very resistant to shearing.<br><br>Generally the lower the first number, the higher quality of base stocks are required. There are no mineral oil 0w-xx oils, only synthetic.<br><br>Your reading that 5w was required to 'maintain pressure' shows that your are reading the wrong information.<br><a href="
http://www.bobistheoilguy.com/motor-oil-101/" rel="nofollow" target="_blank">
http://www.bobistheoilguy.com/motor-oil-101/<br><br></a>MMO's instructions say to add upto 20 percent of the total volume, so if the van requires 5 quarts of oil, 4 quarts of oil and 1 of MMO.<br><br>Changing the filter after 500 miles can be beneficial if the engine is known to be sludged. I like prefilling the filter 2/3 the way before reinstalling to minimize the time it takes pressure to build and get oil back upto the rockers.<br><br>I always open up my oil filters with a chisel and inspect the element for debris, or sludge, or tears, also to see how much ferrous material is caught by the magnets I adhere to the outside of the can.<br><br>The length of hose trick works good, but this is vastly superior:<br><a href="
http://www.harborfreight.com/mechanics-stethoscope-41966.html" rel="nofollow" target="_blank">
http://www.harborfreight.com/mechanics-stethoscope-41966.html<br><br></a>You might find opening the valve covers to be a can of worms if it indeed is sludged. These engines are not known sludgers, but all it takes is a lazy ignorant uncaring previous owner who would say "change it to what?" when asked when the last time the oil was changed.<br><br>Mechanical cleaning under the valve covers is a nightmare if it is sludged. Too much crap can fall below and cause issues, unless the oil pan is also removed and cleaned, which is a huge PITA.<br><br>Get the stethoscope and make sure it is the lifters, and give the MMO time to give results before removing the valve covers.<br><br>I am not sure if your injectors also have the fine stainless steel mesh screen on them as mine do. Mine runs at 15 PSI, yours is closer to 50. Opening the fuel system can be dangerous when it is under pressure. Locating the ASD/fuel pump relay and disconnecting it then cranking the engine will relieve the pressure, among other methods.<br><br><br>