I'm new at this, so bear with me.

I have several vehicles personally and in my company. Many times we exceed our oil drain schedule (10k) many times with no ill affect. I would say our equipment is under the extreme duty catagory and are driven every day. I have yet to have a mileage oil change issue with any one of them regardless of brand. Our highest mileage was with a Chevy V6 at 189,000 hard miles still going strong.

We had a 2002 Chevy Blazer (with 61,000 miles)setting for a year and the oil (Delo 400)only had 300 miles on it. When we started it (several times over several days) we had lifter rattle.The lifter would pump up but rattle again at start up. A quick oil change solved the problem. We have now driven it 1,000 mile with no undue noise.

I have alway heard of oil breaking down with time but this is the first time we have seen it.
We have changed to a Full Synthetic for any that may set for a long length of time. Don't know the outcome with the synthetic as of yet.

Sounds that many of you have much better technical info than I. Maybe you can make an evaluation concerning oil changes and time frames.

Hope this helps someone.

THere is now a new inexpensive media for checking engine condition and oil condition. Like a Eva test, or blood test media, you can place a drop of oil from the oil stick in this paper media and get 4 variables, these are:

contamination (carbon, soot, insolubles, dirt)

Oil condition (oxidation)

Water contamination (condensation, cooling water)

Fuel Dilution (gasoline, Diesel)

With these 4 variables you can get a good picture of attention or action items for engine and for the oil at a fraction of the costs of a regular oil analysis. This is a screening test, not a professional oil analysis like in the laboratory and does not replace the professional lab oil analysis. It is qualitative, not quantitative. But even so, perhaps the tool you are looking for to determine when would it be a good time to change the oil.

We sell motorenew tests in sheets of 6 tests.
Cost: U$29.90 for 1 kit of 6 test, or U$500 for a set of 20 kits (120 test)

Please send us your order to info@motorenew.com We will call you for credit card information.

Distributors welcome

Despite your best intentions, the oil companies will push you in the direction of "change the oil", when in most cases, all that may be required is a better filter. Or, a filter that is improved. While you can't reduce the micron rating of the OEM filter (b/c you would have to increase the size of the filter to maintain the needed flow rate), augmenting your filter's wear metal contaminants-retention-ability, usually will have an affect on your oxidation issue.
Switching to a better oil helps, with out a doubt, only now your oil changes will become more expensive. Check out the following site - www.magneticfiltration.com
This patented system can be applied to any spin-on filter and the results are astounding. Engine lube oils, diesel fuel, transmission, & hydraulic filters, all benefit by way of enhanced filtration.
Common knowledge dictates that the cleaner the oils (& fuels) the longer the oil is serviceable and longer is the life of the equipment.
This System enhances the filter, so as to trap contaminants below the micron rating of the spin-on it is applied to.
Spend some time at the website and you may be rewarded with a service vehicle that will cost you a lot less to operate.

Ex multinational oil company oil product manager with no vested interest
Drain periods are conservative, but for a reason.
Other factors usually limit oil drain periods,largely contamination, for example fuel dilution, poor combustion giving high soot levels, coolant contamination and dirt.
Brave man to extend oil drains without regular oil condition monitoring.
Magnetic filters have no bearing on any of the above but obviously will beneficially remove ferrous debris.

Some engines run relatively cleaner than others but even then I wouldn't extend the intervals based on visual cue, rather I would depend on an analysis.