5-15-08, Update: Oil: Chev. Delo 400, 15w40, TTL Time: 152 hrs Since New, I checked the ball over spring relief valve, it was OK. I was thinking that the engine was over heating, so radiator and bug screen were cleaned, I should have saved the energy. The tractor is so new that nothing seems amiss. I installed a Harbour Freight $10 oil press test ga., to verify the installed oil light. And scared myself. The gage showed 25psi at 1600 on start, that's good, and within 5 min. the pressure dropped to 15psi/1600rpm, that's bad, if I still had the light installed it would have come on. At idle 7psi/800rpm. If I increased rpm to 1800 the pressure went to 20psi, and that's good. On a cooler day it took over an hour to get these numbers. I know that the book lowest normal oil pressure is 14psi at idle rpm and this keeps the light out. So, doesn't look good and I smell an oil pump replacement. I'm still thinking that 20psi oil press and oil light out at 1800 rpm may be OK. After all the pressure is just there to get the oil where it's needed then oil "splash" lubricates. The "oil clearances" provide the space for the oil to prevent metal to metal contact. Oil pressure doesn't push the close fitting parts apart. There is no roughness or noise so I don't suspect a bearing The only thing is: the oil seems very thin when hot, so I'm going to change to straight 30w "by the book" for our summer time temps.. The oil level is stable and not thinned out by a fuel leak, but with five min running time how could it. Since the OAT was 98* today, I thought maybe the oil I used, which is for trucks at highway speed, that just maybe the 15w40 viscosity is too thin for a slow moving tractor at these higher outside air temps. Its probably a long shot but maybe that's the problem. I'm thinking "new engine not broke in yet", still tight and gets too hot for the Delo oil. I looked in the repair manual and there is not a lot of info on changing the oil pump, so must be a rare problem. Anyway that's my next big idea to find the problem. I suppose that's why the tractor came with an oil light, so we wouldn't scare ourselves if we read low psi numbers. Besides, here I am happily tractoring, digging in the dirt at 1700 rpm, the oil pump is providing just enough pressure to keep the light out. Must be OK psi right? How am I going to know that the pressure is below the book psi numbers (47psi at "rated" rpm, presumed 2600rpm) or some such increment of normal psi/rpm. If the light never comes until I'm ready to shut down and I see the light come on at idle. That is no time to find out that for the past 2-3 hrs you have been running at low and damaging oil pressure. Too late to do "the right thing". Seems to me they are setting them selves up for lots of warranty claims if the oil light can't inform when the oil press is low enough to cause harm. So that's my thoughts for whatever they're worth.