How much to pay towards vehicle expenses for using/sharing SO's car? {positive!}

[swashbucklinstache]

Hi,

First the best news is that I'm nearly FI (see journal) and in a long term stable dating relationship with someone with very good finances but not into MMM. So this is on the intellectual curiosity / don't forget about X / MMM people smarter than me weighing in end of the spectrum. The question at hand is what's a good (dare I say fair) amount to contribute to car expenses given they own the car. I don't want to short change them and they asked me to come up with a solution. The question came up now because we moved and as part of that went to 1 car in 2022.

The car:
2017 Ford hybrid with 65,000 miles mostly highway they bought before we met. KBB says worth $16,500 private party.

The usage:
They drive 130 miles a week alone
We go together 10 miles a week, e.g. groceries
I will drive 5 miles a week by my own
Unspoken but they get first say in any desired usage overlap

The expenses:
A car loan that will be paid off in 8 months
Gas
Maintenance
Insurance
Equity that would otherwise be invested?

Notes
City we live in requires car for them but ownership and moving due to ownership is not negotiable to them
We might move in 6 months for other reasons and cut their commute by 20 miles a day
We share rent & utilities 50/50 but not much else with low expenses and opposite diets

The options I've thought of so far:
a) Buy half the car and pay half of everything. This feels like a little too much given relative usage and that if we had no car I'd be happy with that & not looking to buy.
b) I pay half the insurance, half the maintenance including registration & etc., and fill it up any time I use it. Plus half the annual depreciation. No other gas, nothing on the loan, nothing regarding equity.

I'm leaning towards B. Thoughts? Whatever I say will be met with "sounds great" and will be delivered in an annual approximate sum.

[SunnyDays]

In my opinion, both options are too much.  You are driving only 5 miles per week.  I assume that the SO would have to drive the 10 miles per week for groceries regardless of whether you went along, unless you are going to further stores that SO wouldn’t go to on their own.

Do you need to change anything about the car (different tires for example) or carry additional insurance for you to drive it?  Or will you drive roads that will cause undue wear and tear on the car?  If so, then you should pay extra for that of course, but if not, I would just pay them a flat rate per mile (whatever seems reasonable to you) and top up the gas when you drive it.  If SO thinks that’s fair, that seems like enough to me.

[RWD]

58.5 cents per mile.

[hoodedfalcon]

I suppose I find it strange that you feel obligated to pay towards SOs car for such minimal use. I think the IRS mileage rate would suffice if you wanted to pay.

Or just take an Uber if you need a car?

[PMG]

Standard mileage rate sounds reasonable. You could be generous and pay above the irs rate if you really wanted to, but that doesn’t seem necessary.  There are lots of apps out there to track miles (or ye old notebook) driven and you could square up monthly or whatever worked for you two.  That also would support splitting fluctuations fairly whether it be lifestyle creep, or a change in habit or just splitting a roadtrip.

[Paul der Krake]

You're overthinking this. Unless the owner had something specific in mind, I'd just fill it up every now and then.

[CDNSaver]

So a few perspectives you could look at.

The cost of you using their car to them is the opportunity for them to use it plus maintenance plus gas.  Given they have priority the opportunity cost is near zero so by that logic simply the IRS rate would be reasonable or to be more accurate all the total car coats plus depreciation divided by total milage times each persons milage.  This would be fair from her cost

However if you look at it from your benefit point of view I think you get much more benefit.

The first question would be are the 5 personal miles plus 10 joint miles required.  If they are then the benefit to you is a lot more than the IRS milage because you can’t own a car for $10 per week.  So the value of the car to you is what ever the substitution would be for you to travel the essential miles.  So calculate whatever co-op, ride share, uber or cabs would be for your milage plus half of the joint milage.  That would be your benefit from her owning a car.

I think since your milage is so small you should pay the full value of your benefit because in the absence of them having a car that would be your cost.

[ixtap]

Is the insurance more or less with you on it? DH covered our entire insurance when he moved in because it was cheaper than what he had been paying previously. If it is more expensive to add you, you could cover half or even just the difference. The only other concession we made was that when the car you are driving needs gas, you put it in, not matter who has been driving it most lately. I do try to top off any care I borrow.

[Samuel]

It might make sense to check on the insurance and see if you need to be added as a secondary driver in order for you to be covered when using the car on your own. If you live together and use it regularly that might be needed to ensure insurance won't try to deny coverage should you be in an accident. If you go that route you should pay for the (presumably very modest) change in insurance rates.

But for 5 miles of use a week you should just fill it up every once in a while. No need to contribute more, they'd have the car either way it sounds like.

[SweatingInAR]

Is the insurance more or less with you on it? DH covered our entire insurance when he moved in because it was cheaper than what he had been paying previously. If it is more expensive to add you, you could cover half or even just the difference. The only other concession we made was that when the car you are driving needs gas, you put it in, not matter who has been driving it most lately. I do try to top off any care I borrow.

I agree with this!
Pay for your own insurance, plus something close to the IRS cost. Round up, but don't go higher than the rideshar ecost. I imagine if you were to take a lyft/uber, it's a minimum of $10 per trip leg. $20 for a round trip.

[swashbucklinstache]

Is the insurance more or less with you on it? DH covered our entire insurance when he moved in because it was cheaper than what he had been paying previously. If it is more expensive to add you, you could cover half or even just the difference. The only other concession we made was that when the car you are driving needs gas, you put it in, not matter who has been driving it most lately. I do try to top off any care I borrow.

I agree with this!
Pay for your own insurance, plus something close to the IRS cost. Round up, but don't go higher than the rideshar ecost. I imagine if you were to take a lyft/uber, it's a minimum of $10 per trip leg. $20 for a round trip.

I think I'm looping around to something a bit more than the IRS per mile cost. I am on their insurance and will pay the additional costs for adding me there too. What I'll probably do in the end is mentally very roughly track the miles per month in my head and at the end of the month hand them cash somewhere between the IRS and Uber costs minus whatever gas I put in, which I'll likely do just to minimize inconvenience for them. In practice that'll often be a negative number.

'my benefit' thoughts are definitely where I was coming from, as @CDNSaver described.

Thanks all!

I agree I'm overthinking this but it is a fun distraction from moving =). Partially just mentally getting used to car costs for not a 17 year old subcompact =).