For the fifth time this season – and the third time in the last four race weekends – IndyCar's starting grid will look a bit different than the previous day's qualifying results, due to grid penalties handed out by the series for entries surpassing the four-engine allotment allowed under IndyCar's current rulebook.

Here are how those are handed out:

How many engines does each full-season IndyCar entry get per season?

To accommodate IndyCar's 17-race regular season, along with each car's allowed test days and the ample hours of practice available during the Month of May for the Indianapolis 500, each full-season entrant gets four engines from their team's chosen manufacturer -- as part of an annual lease price of more than $1 million -- with which they can run up to 10,000 miles. Teams then are allowed to change out engines every 2,500 miles, and personnel are assigned to keeping track of that mileage and plotting their use during practice, qualifying, races and testing so as not to have them exceeded their prescribed lifetimes at the risk of losing performance.

But when teams and the manufacturers run those engines at their limits to extract the most performance possible, sometimes those engines 'blow up' or become damaged beyond repair. When that happens before they've reached their 2,500-mile lifespans, that entry is then likely to incur a grid penalty before the end of that season.

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When are engine change penalties assessed?

IndyCar's rulebook doles out penalties to teams once they've used a fifth engine for that season, should it be deemed "unapproved." An approved engine change can come if a team uses up the mileage allotment for all four of its original engines before the end of the season; ahead of a manufacturer test; ahead of the Indianapolis 500; for special events; or in order for an engine to be repaired.

Any change not explicitly identified as an approved engine change is deemed an unapproved one.

Penalties are dolled out the race immediately following the engine swap, with a penalized entry losing six spots on the grid at a road or street race, and nine spots for an oval race.

Sometimes, due to mechanical failures, an entry will require more than just five engines in a given season. When that occurs, the entry is given the appropriate penalty the race immediately following it being fitted with a sixth, seventh, etc. engine of that season.

Why is there a limit on engines per entry?

Though it may sound counterintuitive, IndyCar's pair of engine manufacturers are actually fans of this rule -- in order to help them both curtail their expenses. If teams and manufacturers could run an unlimited number of engines in a given entrant, towards the end of each season, we'd start to see cars in the hunt for a championship receiving new engines almost every race, so as to ensure those title-contending cars had the best technology possible.

But each of those new engines costs money.

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These teams and manufacturers compete in this sport first and foremost to win, though, so they would naturally do whatever it took to achieve those goals. The grid penalty in place for entries that run more engines than allowed in a season serves as a detriment, in hopes that any advantage gained by using a fresh engine would be counter-balanced by a car starting further back in the field for the next race.

Additionally, cars on their fifth (or more) engine of the year are no longer able to accrue manufacturer championship points for their team's engine manufacturer. Those points are built by taking each OEM's top-two finishing entries from each race and tabulating those points throughout the season. When a car can no longer accrue points for its manufacturer, that entry is taken out of the finishing order used to determine manufacturer points for the remaining races.

How many penalties have been handed out in 2024?

Ahead of this weekend's race at Portland International Raceway, IndyCar handed out six-spot grid penalties to Rahal Letterman Lanigan Racing's No. 15 Honda (driven by Graham Rahal), Andretti Global's No. 27 (Kyle Kirkwood) and Meyer Shank Racing's No. 66 (David Malukas). Rahal's comes after he suffered a failure at last weekend's race at World Wide Technology Raceway -- requiring a seventh power unit of the season.

Meyer Shank Racing's No. 60 Honda (Felix Rosenqvist) and Chip Ganassi Racing's No. 4 Honda (Kyffin Simpson) are both on their sixth engines of the season with four races left in 2024. Ganassi's Nos. 9 (Scott Dixon), 10 (Alex Palou) and 11 (Marcus Armstrong) Honda entries, as are Rahal Letterman Lanigan Racing's No. 30 Honda (Pietro Fittipaldi) and Dale Coyne Racing's No. 51 (various drivers).

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That makes 10 of Honda's 15 entries having been affected by premature changes this season (for 14 total unapproved changes in all) -- largely due to a run of failures the manufacturer experienced in the two-week lead-up to this year's 500. Between the Sonsio Grand Prix on the IMS road course and Indy 500 qualifying, Honda made seven unscheduled engine changes for six different drivers (including twice for Rahal).

Chevy, who currently has all 12 of its full-time entries just on their four engine of the year, experienced its own issues that month, with seven cars experiencing plenum events (essentially a brief hiccup) during qualifying weekend -- six of those instances occurring during drivers' qualifying attempts.

This article originally appeared on Indianapolis Star: IndyCar: Why teams, drivers get unapproved engine change penalties