There’s no simple answer to this. The computer program that controls when the hybrid system chimes in to help with the petrol engine is a very complex one and depends on a lot of inputs. For instance, the driving mode you’re using will vary this, so will the amount of charge in the battery at the time and even how aggressively you’re driving.

As time and kilometres go by, the condition of the battery would also probably make a difference, as can what accessories (air conditioning, for instance) you’re running at that moment in time.

Apart from the obvious requirement to change to 17-inch wheels as well as your chosen tyre, there are legalities to be considered here, and they can vary from State to Territory, so you need to check with your local authorities before committing to any change like this. However, broadly speaking, you can increase your wheel size by up to two inches, provided you don’t throw your speedometer out in the process. You also need to stay within a certain percentage of the car’s original rolling circumference (the distance the tyre travels in one revolution) to remain legal. And there are the practical issues such as tyre-to-bodywork clearance.

However, on the surface the swap you’ve nominated should be legal and practical. The 2000 Lexus LS400 originally came with a 225 60/16 wheel and tyre, so your preferred option only increases wheel diameter by one inch. Also, by fitting a 55-series tyre, you’ve reduced the sidewall height (from the standard 60-series tyre) so the rolling resistance of your new combination will be less than one per cent larger, so shouldn’t create any legal or clearance hassles. Just be sure to let your insurance company know you’ve made the change. Be sure to check the accuracy of your speedometer after the change, too. A GPS speedo app on your phone is the easiest way to do this.

The Lexus GX 550 went on sale in Australia in June, 2024.