Car Servicing

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Every time I take my 2017 Mazda CX-3 for a service, it comes back with higher fuel consumption. At the moment, the consumption is 7.9 litres per 100km. I'm spending a lot of money putting petrol in the tank.
At the last service of my 2019 Subaru XV, the dealership advised "front lower control arm bushes are split will need to be replaced". Subaru has so far refused to do repairs under warranty which expires at the end of March 2024. The car was bought new in March 2019. It had done (at the time of service) 45,778km. It has never been off road. It has never towed anything and doesn't have a tow bar. Subaru is claiming normal wear and tear and driving style are responsible and therefore not a warranty matter. They refuse to say what driving style would do the damage.
Is the number three cylinder blowing in my 2017 Ford Ranger Wildtrak covered under warranty?
The outside temperature gauge in my 2015 Holden Captiva was showing high numbers, then the air-con stopped working. Was this because of the weather conditions?
I bought my Opel Astra new as a demo model and while it is a beautiful little car, I've had every one of the issues I now realise the model is infamous for! I've spent a fortune fixing most but currently have a serious oil leak, presumably from the turbo - probably another $1500-plus to fix. My question: Is there a point with these cars where I can assume issues are fixed and keep it, or should I cut my losses?
Where can I go for a verified Lexus service centre other than the Lexus dealership?