Own an '09 Accord and I'm getting real close to changing the oil for the first time. I used Mobil 1 religiously in my old vehicle (still own it.) However is it really necessary and worth the extra expense, about double the cost at least. I'm not changing it when the automatic reminder tells me too, I'll do it sooner.

Absolutely. Honestly, I think people are crazy not to use full-synthetic engine, transmission, and power steering fluid. It's the single most important preventive maintenance step one can take. The differences between synthetic and conventional oil are huge!

It's also worth it to use a premium oil filter; e.g. Purolator Pure One or Mobil 1. Change full-synthetic engine oil and premium filter every 6,000 miles or 6 months, whichever comes first.

Hope some other experienced, self-maintenance drivers reply to your question about Synthetic motor oil; we need more variety of replies. I believe all modern car engines can last to their normal life expectancy (over 200,K miles) using either synthetic or natural oils given normal, routine maintenance as recommended by the manufacturers. Today's major-brand motor oils are all very good and can fully perform up to and beyond manufacturer's recommended change intervals. Of even more importance, which some people do not fully recognize, is the oil filter quality and its useful life. Given that the original intent of synthetic oils was to perform well and be changed at 15,000 mile intervals, the problem was that oil FILTERS were (are) not made to also last that long without serious filtration deterioration. So to make cost of synthetic oil more reasonable, especially in your 2009 Honda, be sure to also follow the typical 7.500 mi oil and filter changes. Also use quality oil filter (over 96% single pass or 99% multi-pass efficiency) at every oil change. Of course this all assumes you are an average no-Jack-Rabbit driver, and not a Tuner, Slider, Off-Roader or Trailer Tow'er. And last but not least, always be aware of the mutli-BILLION Dollar Automobile Accessories Association industry that makes its handsome living through their highly Advertised oil products and myriads of other second echelon automotive supplies.