IndyCar engine suppliers Honda and Chevrolet have extended their agreements with the series to continue supplying teams.
Honda has been ever-present as an IndyCar supplier since 2003 and this season welcomes Chip Ganassi Racing back to the fold as it bids to topple the dominance of the Penske-Chevrolet partnership.
Chevrolet returned as an engine supplier with the introduction of the current Dallara IR12 chassis ahead of the 2012 season, and has powered all but one of the five eventual drivers' champions since then.
IndyCar announced on Friday that both manufacturers had signed undisclosed multi-year contract extensions to continue as suppliers, on the eve of this weekend's season-opening race in St Petersburg.
It also means that all four of IndyCar's current major suppliers have committed to the championship.
Tyre supplier Firestone and chassis manufacturer Dallara having also signed contract extensions - Dallara having outlined concepts for an updated, standardised bodywork kit for 2018.
"This is a unique moment in the recent history of the IndyCar Series," said IndyCar president of competitions and operations Jay Frye.
"To have all of our major manufacturers locked in with us for the foreseeable future points to the fact that they all have bought into the vision for the IndyCar Series.
"It's another sign of the positive momentum we continue to build as we grow this sport into the next decade."
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