I use Synthetic also- because its good for a long time. With reg oil I do a change every 5K. I don't stress with Synth. It last much longer. But I usually will change it between 5K and 7500 mi. I have 10K on car now.

 

I believe I mentioned it in another thread, but I'm switching to Royal Purple on my next oil change at 15K miles which should be approximately two weeks from now. I have 13K on it now. I average anywhere from 1200 to 1800 miles a week. Most all of which are highway miles. I did my first oil change at 4K miles and the NIC read 51%, my second oil change was at 10K miles and the NIC read 24%. My plans are to switch to Royal Purple after which I will change the filter and add a quart every other oil change. I have done this in my Silverado since '04 and have not had any problems with it. Also, this helps offset the cost of the Royal Purple, I still come out averaging about $34 per oil change. ($56.95 for the full oil change, $9.95 for a filter swap and quart of oil). To each their own, just my $0.02....

CBL

 

Dan,
with all the fleet/police usage. did anyone ever do an oil anaylsis to see the condition of the oil ? Passenger vs fleet or 3000 vs 7500 mileage change?