We can't stress the importance of lubricants too much, because they are the main factor in determining friction. Motor oil is commonly used because of it's ready availability. But, it is important to realize that the reverse is also true. If the recommended tightening specifications are based on the use of a special lubricant, the use of motor oil or other non-specified lubricant will result in insufficient preload. The torque must be increased to compensate for the added friction induced by the non-specified lube.
Surface finish is also a contributor to the friction factor.
A black oxide finish, for example, behaves differently than a polished fastener. So you see it is very important to closely observe the tightening recommendations supplied with each type of bolt. Without a method of accurately measuring the stretch, it is very easy to exceed the yield of the material and essentially fail the fastener before you install the oil pan. Absolutely, if you follow the principals of stretch. Because it is bolt stretch that provides clamping force, we primarily recommend the use of the stretch method.