5 litres of diesel in a petrol car

Put 5 litres of diesel in a petrol car? That’s like tipping gravy into a cappuccino—do not even turn the key. Diesel won’t combust properly in a petrol engine; it can foul plugs, clog injectors, and make it run like a lawn mower with a hangover. With about 5 L in the tank, the risk hinges on the total fuel—if that’s anywhere near 10% contamination, don’t roll the dice.

Best move: don’t start it; get it towed, have the tank drained and the fuel system flushed. Expect around AUD $250–$500 for a roadside drain, or $400–$900 at a workshop; if you drove it and it misfired, you could be up for $1,000+ in cleanup and parts. Afterward, refill with fresh 95/98, replace the filter, and keep receipts—some insurance policies cover misfuelling.