Post by neil on Apr 11, 2012 16:53:34 GMT -5
Here's a subject that can get very heated.
I'm going to explain when not to use synthetic and why.
You don't want to switch your gear oil over to synthetic in your axles much after 10K miles of a re-gear or rebuild, and I don't suggest switching on a stock vehicle axle that has never had synthetic in it from the factory.
To answer why......
Synthetic does have alot of benefits, and it may or may not give you an extra mpg, but I've yet to see it myself. It works very well at maintaining near new build specs and clearances because of it's low wear properties.
The reason it's not good to switch to on higher mileage is because the difference in the basic molecular properties compared to conventional oil.
Synthetic maintains a uniform molecule that is generally smaller than that of conventional. Conventional on the other hand has multiple size molecules that are in general, larger than synthetic.
Bearing to race contact is minumized by the oil, but wear does still occur. If you were to look at a bearing run for 50K miles on conventional under a microscope, it would like parallel grand canyon's over the entire surface. This is not a bad thing with conventional oil because these canyons actually help to hold the oil on the surface better.
Synthetic on the other hand would look more wavy on the race surface, because the uniformly small molecules move more as a whole and contribute to less wear of the metal sufaces in the long run.
When switching from conventional to synthetic, the synthetic does not have the moleculer size to fill the afformentioned canyons. That allows the bearing to contact the ridges between the canyons and begin rapidly wearing away the race and rollers alike.
This can lead to oveheating of the bearings(generally blackened races, loss of pinion preload....which in turn causes a leaking pinion seal, rough feeling or noisy gears and ultimately ruining the rear as a whole).
You would also notice that the gear faces will also show the affects of the oil change. They lose their mirror shine and become dull and scored.
It is advised to break in gears on conventional so as to pre smooth and start adding the fisures to the metal surfaces to help the synthetic adhere to them.
At which point it is the best time to switch, roughly 1500-2k miles of break-in.
I build custom axles and rebuild axles, and believe it or not, 90% of all rebuilds come from a switch to synthetic between 50k and 100k miles. If I did not see this commonly, I would not be offering the advise. You will notice problems, generally with-in 6k miles of the change.
Everyone knows tons of people who switch on high mileage with no problems, and I don't deny that myself, but if you are one of the unlucky, a $40 oil change can turn into a $1200 repair pretty quick.
The choice is yours, I'm only advising.
I'm going to explain when not to use synthetic and why.
You don't want to switch your gear oil over to synthetic in your axles much after 10K miles of a re-gear or rebuild, and I don't suggest switching on a stock vehicle axle that has never had synthetic in it from the factory.
To answer why......
Synthetic does have alot of benefits, and it may or may not give you an extra mpg, but I've yet to see it myself. It works very well at maintaining near new build specs and clearances because of it's low wear properties.
The reason it's not good to switch to on higher mileage is because the difference in the basic molecular properties compared to conventional oil.
Synthetic maintains a uniform molecule that is generally smaller than that of conventional. Conventional on the other hand has multiple size molecules that are in general, larger than synthetic.
Bearing to race contact is minumized by the oil, but wear does still occur. If you were to look at a bearing run for 50K miles on conventional under a microscope, it would like parallel grand canyon's over the entire surface. This is not a bad thing with conventional oil because these canyons actually help to hold the oil on the surface better.
Synthetic on the other hand would look more wavy on the race surface, because the uniformly small molecules move more as a whole and contribute to less wear of the metal sufaces in the long run.
When switching from conventional to synthetic, the synthetic does not have the moleculer size to fill the afformentioned canyons. That allows the bearing to contact the ridges between the canyons and begin rapidly wearing away the race and rollers alike.
This can lead to oveheating of the bearings(generally blackened races, loss of pinion preload....which in turn causes a leaking pinion seal, rough feeling or noisy gears and ultimately ruining the rear as a whole).
You would also notice that the gear faces will also show the affects of the oil change. They lose their mirror shine and become dull and scored.
It is advised to break in gears on conventional so as to pre smooth and start adding the fisures to the metal surfaces to help the synthetic adhere to them.
At which point it is the best time to switch, roughly 1500-2k miles of break-in.
I build custom axles and rebuild axles, and believe it or not, 90% of all rebuilds come from a switch to synthetic between 50k and 100k miles. If I did not see this commonly, I would not be offering the advise. You will notice problems, generally with-in 6k miles of the change.
Everyone knows tons of people who switch on high mileage with no problems, and I don't deny that myself, but if you are one of the unlucky, a $40 oil change can turn into a $1200 repair pretty quick.
The choice is yours, I'm only advising.