oil change high mileage on 2003 Chevrolet Monte Carlo

i go to NTB (national tire and battery) to get my oil change and i always get the cheap oil, and they always recommend that get the expensive one because i have high miles on the car (89,xxx) would it really matter if i got it or not and yes i do want this car to last a long time but i need to know for sure if it really matters, the expensive oil is the Synthetic Motor Oil, the cheap one is the conventional motor oil

by in Chicago, IL on August 27, 2010
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1 answer
ANSWER by , August 27, 2010
I started using full synthetic oil about 10 years ago, my last car got 336,000 miles on the engine with out ANY major repair needed. I actually sold the car for $750 because it still ran well enough to pass the State Emissions test. So yes, I am a firm believer. I use Mobil 1 full synthetic and change it every 4000.