Ricepop:
Your 16k miles PA explains why your GFV was a bit lower than what I was given on my VW finance offer (didn’t take up the finance, my dad lent me the money at 2.9% - the same rate he gets from his ISAs right now).
Let’s generously assume that the insurance will be the same, nothing will go wrong that requires fixing with your 5 year old GTI and you will get servicing done as cheap as the VW 3 year pack you can get on your new GTD.
For you then, based on previous assumptions, regardless of who is picking up the tab on fuel:-
£10k GTI, add 48k miles and we’ll optimistically estimate it to be worth £4500 at the end:-
£5500 depreciation
£8480 fuel (35mpg @£1.35/L)
£780 tax
£400 ½ cost of tyres and brake pads all round
Total 3 year cost = £15159.
£11625 depreciation (based on your actual purchase cost and GFV which is lower than likely p/x value)
true depreciation is likely to be £10660, taking your GFV and dividing it by (0.9333 = the ratio of my GFV of 56% to likely actual p/x value of 60%). That car should be worth approx. £14500 in p/x with circa £50k on it vs £15500 I expect for mine with 30k miles on it (my GFV was 14400).
£5596 fuel (55mpg @£1.40/L)
£40 tax (2 x £20, first year is free)
No incidentals cost
Total 3 year cost = £17261 based on your GFV or £16296 based on a realistic future p/x value.
The difference there of £2102 (or £1137) over 3 years is pretty much all down to your options holding almost no value, or lack of discount (as I’m not sure what options you have apart from the satnav you mention). There is interest to consider if you have £10k to put down too.
You have to be doing 42mpg in the GTD for 15p a mile to pay for your fuel (easy). You’d get £1200 PA tax relief in 40% of the fuel differential (15p vs 45p) for 10k miles PA.
You have to be doing 34mpg in the GTI for 18p a mile to be paying for your fuel (not as easy). You’d get £1080 PA tax relief in 40% of the fuel differential (18p vs 45p) for 10k miles PA.
