Unless you will be driving at least 15,000 miles a year, diesel cars are no longer a "sound investment" when there is a viable petrol alternative. The emissions kit alone on a diesel engine (EGR, DPF, SCR) is not long-term reliable and will almost inevitably become troublesome and expensive to fix by 80,000 miles, and, if you drive only short distances, you can expect regular trouble with the DPF. The problem is, for many bigger cars such as SUVs, there aren't always viable alternatives, though for them petrol hybrid drivetrains are being developed and work. For example, even without plugging it in, a Volvo XC90 T8 PHEV is 25% more economical than an XC90 D5.