I have a 2010 f150..the manual says to changw the oil every 7,500 miles. Most of my driving is city, but once a week i tow my boat 200 miles on the highway.

Is this enough towing that i need to change the oil at more frequent intervals?

 

I believe that due to your frequent towing, your truck qualifies as being used in "harsh or severe" conditions and the oil should be changed on a 5000 mile interval. You should see the owners manual, it clearly details the conditions and intervals.

 

I wonder how much your boat, motor, and trailer weigh ? I think that it would be an important part of the equation.

 

Though the owner's manual doesn't give great detail on what it considers severe conditions (towing 1/year with a 1K load or 1/week with a 7500 lb. load), I agree with Gerrard that you should be changing your oil at 5K intervals. If you really want to know how your oil is performing, get an oil sample and will tell you what intervals to be changed. 5K is a good round number which I end up at and tow about 1 - 2/week during non-winter months.

 

Motorcraft oil and filters are cheap. I would change it more often than recommended.

 

If you want to know exactly how the oil you are using is performing, you need an analysis report. A spectroscopy will tell you the wear metals in the oil and if you decide to do the report, I'd suggest getting the TBN as well. The TBN, Total Base Number, is the oils ability to handle combustion acids. Not all oils respond the same even in the same engines due to driving conditions. If you're happy with the brand oil you are using, get a report on it. It may surprise you-good or bad, but at least you'll know. If you decide to change brands, you'll need another report. Cost for a standard test from Blackstone is 25 bucks. The TBN costs a little more but in your situation, worth the money.
http://www.blackstone-labs.com/free-test-kits.php

 

Thanks guys. My boat and trailer are fairly light...approx. 2,500 lbs. I think ill hit the oil analysis place too...it will he great to avtually quantify what is going on with the oil.