Can you really get like 15,000 miles out of some of the Synthetics out there? Has anyone tried?

 

Synthetic oils can take it, its the filters that cannot hold that much foreign material. If you were to do extended drains on your oil, you should be replacing your filter every 5-6k miles with a quality filter. This will replace about 1 quart of oil every 5-6k miles. I was on extended drains with an oil analysis being done every filter change on my Bonneville. To be honest, it ended up being cheaper to just change the oil instead of doing the analysis. What the analysis did tell me is that the oil was still lubricating the engine very well even after being in there for 18k miles (3 filters) on a 5qt system. So you figure that each filter change, I was replacing 20% of the oil. To know how long the oil will last, that is HIGHLY dependent on the engine and I wouldn't recommend extended drains unless you start off by doing a regiment of oil analysis testing over the first drain period (whatever you are comfortable with) to get a baseline.

My oil analysis was done by a local (at the time) lab that charged $10 per analysis. I have since moved and shipping would be a killer, but BlackStone-Labs.com will do one, but for more money than I'm willing to spend. Although my Rainier now uses 7qts of oil to fill the crankcase... I may have to get back into doing this now.

 

I would say that it would not be wise to run oil past 5000 miles. Thermal breakdown will not occur in synthetic oils as much as natural oils. After 5000 miles of running, oil will pick up small contaminates that will not be filtered out by ACDelco orMotorcraft filters. A Wix, Fram or K&N oil filter would be a necessity, but those filters may cause engine to idle rough and cause dry starts with high mileage engines.

 

I thought that AC Delco filters used wix filter internals?

I know Delco isn't in the same class as Motorcraft, lol

 

While we're on the topic of filters, Delco's are pretty good filters. For the money, you can't beat Purolator PureOne filters, but Napa Gold & Wix are right there with them. Also good, but more expensive are the Mobil 1, K&N, and Amsoil filters. Too much $$$ for me though. Motorcraft are good as well.

Fram, however, will never get any of my money. I have personally witnessed 3 engines die due to fram's crappy (at the time) design. 2 by the outer casings just coming off of the mounting plate (burst).

 

GAH! thats no good, im definately getting rid of the Fram on Dale then. I had no idea those had any issues. Guess im going back to good old Delco (only bought the Fram because it was on sale).