Research by the folks at Zero Friction Cycling  detailed in this document here (see in particular page 16) has shown just how much difference a thoroughly cleaned and lubricated chain can make to a cyclist's power output. A cyclist pedalling at 250watt load who pays only average attention to Chain Maintenance, will likely be losing between 15 and 20 watts to friction in the drivetrain. Whereas a cyclist who ensures the chain is in tip-top shape will see only a 5 to 8 watt loss. 

We have taken the midpoint values between these two ranges - 17.5w and 6.5w - for the first row of the table.

The second table row shows the power from the bike after drivetrain loss when a rider is riding at 250 watts (i.e. 250 watts minus the value in the first row).

We then use this respected bike speed calculator which models the speed a bike will reach given a set of input values. The values we have used are 75kg for the rider weight (which, according to Wikipedia, is Simon Richards weight - see below why this is relevant) wheel type tubular, hands on the hoods and we kept the default 8kg bike weight.  We then executed the calculation for three different gradients; 11% (the average gradient of the hill used in the GCN video), 8% (a more common gradient encountered by road cyclists) and 0%.  

Obtaining a calculated speed, we present the percentage improvement in the final column.

We then repeated the calculations but for a rider power output of 300w. We adjusted the Power Loss values in accordance with the the fact the Power Loss is in a near linear relationship with cyclist power output (to be conservative, in increasing 250 watts to 300 watts we multiplied the power loss values by only 1.16, not 1.2). 

In this video the folks at GCN have shown the performance advantages that can be obtained by upgrading from a mid range c.£1,000 bike, to a c.£5,500 Superbike. We have taken Simon Richards’ results from this video expressed in seconds.