My 980 has the long range tanks. I know this because, on the pre-buy, we opened up the panels and looked at the bladders.
Yet, for the past 4 years, I cannot get more than 3,000 pounds in the airplane. Lately, it's been more like 2,900 (but that might be due to warm fuel). We calibrated the fuel gauges, so I know they're right, and in that process took it down to completely empty and filled it up-- 3,000 pounds.
Anyone ever seen this before?