Originally Posted by
Nikko
Question #2 regarding oil changes (on Crossfire's, or any other vehicle for that matter):
Something I've always wondered, and Im hoping someone has an answer to... I've always read that prior to changing a vehicles oil, a car, bike, etc should be started and run for a period of time to warm the oil, and then drained and changed.
So here is the question: assuming the vehicle was run and turned off after the last time it was driven prior to an oil change, and the hot oil drained down into the pan at that time (along with whatever crud drained down with it), why should the engine be started AGAIN, recirculating all that old oil and crud back up into the engine again, when all that old oil and crud was ALREADY down in the pan in the first place?
I would think that since the oil was hot when the vehicle was turned off from its last drive, it already drained down as much old oil and crud as it was gonna do in the first place (and has had significant time to do so), so why recirculate all that old oil and gunk again just to warm it for an oil change, and potentially not get all the crud down to the pan which was probably already IN the pan from the last time it was driven??
OK, this one is going to make about three details/assumptions (akin to yours). The oil being heated flows more quickly when warmed to operating temperature (draining contaminants more quickly, not settled on oil pan). Also, any moisture in the lower end (all oil paths) inherent to an engine, will be evaporated, with less contamination to the new oil. Finally, many use a 'topsider' type oil changer (draw oil out of pan through the dipstick tube) and if it is 'cold' it makes it harder to get it out due to a higher viscosity when cold. The instructions for the 'topsider' type devices instruct to run to operating temperature, solving all three points above (except obviousely the people who drain through pan drain BUT the oil will still have the contaminants better suspended IN the oil not 'on the pan').