Simple answer. - "Oil is always cheaper than metal." There a 3 dirties that kill any machine - lift trucks, automobile, farm tractor, etc.

1. Dirty air
2. Dirty oil
3. The Dirty B@#t^*d that didn't change 'em.

Personally, I change my oil in my automobile every 3 to 4000 miles & transmission every year - I pull a bass boat on weekends. Have a 1998 Explore w/ V-6 - and have 211,000+ miles the engine runns fine - uses less than 1/8 of a quart of oil between cahgnes, transmission works fine - I haven't had a payment for many years - I now have a good ROI. I drive it a lot in stop & go traffic in Atlanta now. I