NEWMEXCOBRA To the new owner, try and find the old owner ans see what they ran and run he same. If can not find, you will need to do some testing of different brands to see what makes and keeps the motor happy. I race and have been using 15W40 rottella
oil for diesels. This is cheaper and has all the
zinc and pho. you need for a motor. IF you run a heavy
oil that is higher than a 10-40, Need to give the motor a couple of minutes to get some heat in the
oil. Want to see about 130F on the gauge before driving or revving the motor. I don't know what oil pan is on the car but if it's a stock pan over fill pan by 1 quart. Other note add 1/2 bottle of Lucas oil suppliment. This is a clinging oil that prevents dry starts of the motor. need to install slowly when motor is hot. Temp note on oil, this is a biggie, when driving check the oil temp after 15 minutes of driving, you want the temp in the 180F range. If the oil is too cool, it doesn't help protect the parts as well, same as being too hot. You may want to block off the oil cooler if you are running one to check this out. The most the oil temp should be is about 10-15 degrees over coolant temp. Last note keep an eye on idle oil pressure. IMO if you have 10-15 psi this is not enough to oil the top of the motor.Want to see around 30-40 hot at idle. This may up or lower the weight of your oil too. Last note, NO idling the motor unless you have too, this is a killer with solid lifter motor. Rick L. Ps NEVER UNDERFILL!! The only reason for this is if you have a rear mainseal that leaks and just about all fe's do put paper on the floor.