It's been 5k miles since I last changed my oil, using the Mobil1 5W40 Turbodiesel oil. In those 5k miles, I've had to add 5 or 6 quarts. It's not leaking, I guess it's burning. So, it's not like I have 5k mile old oil in there, so do I really need to spend $50 on 8 quarts or can I just change the filter and assume all to be well in lube land?

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1983 MB 300SD Turbo Diesel