Re: I'll stick with diesel if it's all the same to you
"I've got a small 15 year old petrol car. Don't drive much, and it's perfectly adequate. How is it "green" to throw away cars after 8-10 years?"
In your case, it's not very green. You've already made the bulk of the environmental impact in the production and long running of your existing car - keep doing what you are doing and only replace your perfectly adequate car once you have to (ie it is beyond reasonable repair). Replace "car" with "stuff" in that last sentence and the old hippy in me is summing up a lot of what he thinks is wrong with the industrialised world today, sigh.
However, once you are at that state of needing to replace it, that's when it's worth making the decision between what type of car, trading off things like the relative environmental impact of initial production, long term running, your own likely mileage etc. And it's not a simple consideration as many of those environmental impacts are different and can't be easily compared. For instance, how different is the impact of mining the lithium for your new EV from the CO2 emissions over the lifetime of an ICE vehicle? One form of habitat damage Vs another, so which is your preference?
A few years ago, I think it was jaguar who ran some adverts saying that the CO2 emissions from building their EV was about the same as from 50k miles of driving their ICE version. Even if that figure was accurate, it was only one aspect, didn't account for the impact of refining the oil to burn, the mining of the materials for the battery, recycling of the vehicles etc.