Is it worth it to save the extra money to use this from Heathrow
Terminals 123 [London Underground] to Upminster saving £1.10?

Alternative oyster single fares:
Route 1: Avoiding Zone 1 via any of Kensington Olympia, Shepherds Bush
or West Brompton
Oyster
£2.20Monday to Friday from 0630 to 0930 and from 1600 to 1900.
£1.30At all other times including public holidays.
To ensure you are charged the appropriate fare you must touch on the
pink card reader on the Oyster route validator if interchanging at
Kensington Olympia or West Brompton
Route 2: Avoiding Zone 1 via Gospel Oak
Oyster
£2.20Monday to Friday from 0630 to 0930 and from 1600 to 1900.
£1.30At all other times including public holidays.
To ensure you are charged the appropriate fare you must touch on the
pink card reader on the Oyster route validator if interchanging at
Gospel Oak
Route 3: Avoiding Zone 1 via Stratford (London Overground)
Oyster
£2.20Monday to Friday from 0630 to 0930 and from 1600 to 1900.
£1.30At all other times including public holidays.
To ensure you are charged the appropriate fare you must touch on the
pink card reader on the Oyster route validator if interchanging at
Stratford (London Overground platforms)
When you pay as you go, you must touch your Oyster card on a yellow
reader at the start and end of your journey. If you do not, you will
be charged a maximum cash fare.
Some journeys have been defined as requiring travel via Zone 1 and
will be charged