Regarding this:
- I did not realize that my car cost $3.65 + $3.17 + $15.62 = $22.44 a day to run.
First of all, I think your actual cost of operation is potentially higher than you are computing it to be; because you are ignoring maintenance (i.e. oil changes, etc) and "wear & tear" costs (tires, wiper blades, brakes)... and over time, those can easily equal (or exceed) the cost of gasoline (i.e. each being about 1/5th or 20% of the total cost of operation).
OTOH, since you are probably using the "monthly payment" you are also not computing the residual (trade in or resale) value left in the vehicle -- so that probably balances it out the other way.
Secondly... I find that -- rather than a PER DAY cost -- it is generally ALSO helpful to compute that down to a PER MILE cost. (And BTW if you are "typical" in putting on around 14,000 to 15,000 miles, then your annual costs are right around what the IRS has computed: ~57.5 cents per mile; though again)
Why is it so useful to think on a per mile basis -- especially since your "car payments" and "car insurance" are based on time (for the former monthly and for the latter either monthly, quarterly, or semi-annual) -- rather than miles.
Because if/when people only (or solely) think of their car in terms of monthly costs, they tend make a lot of needless/wasteful trips -- and to be oblivious to the mileage they are putting on -- as a result not only are they burning up more fuel, they are increasing the wear and tear on various components (tires will need to be replaced sooner, sometimes significantly sooner; per example every ~3 to 4 years if you put on > 15,000 miles a year, versus every ~5 to 6 years if you put on < 10,000 miles per year), and of course the more & quicker the total accumulated mileage goes up, the faster the remaining resale value will go down.
By contrast people who think in terms of a "per mile cost" tend to PLAN their trips (and especially their "shopping" patterns) -- we've all heard (and shook our heads at) the stories about someone engaging in the "inane" practice of driving all the way across town (putting on 50 or even 100 miles) to "save a buck or two" on some rather trivial purchase. But the plain truth is that unless we are CONSCIOUSLY thinking in terms of a "per mile cost" we can all easily fall into that kind of a mistake. Because at 57.5 (or just round it up to 60) cents per mile, that addition 50 miles is costing them $30, and an additional 100 miles costs $60 (it's just not recognized/realized because most of that cost -- about 1/2 of it -- is in the vehicle depreciation, not the gas or insurance).
And what that means... is that the next time you "balk" at buying something for say $60, when you know it might (possibly) come on sale a month from now for $40 (or even $30) -- and you then make some "special trip" to buy it during that "spring sale" -- well, you really HAVEN'T saved anything, and (depending on how many miles distant that store is) you may have actually spent MORE by delaying the purchase and making two trips instead of just buying the thing when you first saw it. Ironic, isn't it?
It even plays out in seemingly trivial things. Say you need something small like eggs & bread -- and the "normal" grocery store you frequent is a mere 10 miles away (20 miles round trip); but there is a "quickie mart" just a mile away (2 miles round trip). Is it worth driving (special trip) to the grocery to just to buy eggs at $2 and bread at $1 ($3 total), or should you hit the quickie mart and with eggs at $4 and bread at $2 (GASP!) pay DOUBLE what the grocery charges??? Well at 60 cents per mile, the TRUE cost of going to that grocery to make a $3 purchase is actually $15 (20 x $0.60 = $12, +$3 = $15), whereas the total TRUE cost of the quickie mart trip is actually HALF that, a mere $7.20 (2 x $0.60 = $1.20, + $6 = $7.20).
Most people -- who think ONLY or chiefly in terms of fuel (and compute the cost on "miles per gallon" and "price per gallon") -- will make the mistake of thinking that the grocery is the "better deal."
And it may not seem like much... but if (like most people) you end up making at least one "special trip" like that each week... well, that extra $7.80 per week adds up (just THAT one little behavioral practice alone could/will be a cost difference of an extra $400+ per year -- and end up amounting to an extra 1,000 miles on the vehicle each year). People just don't realize/recognize it as a "loss/cost" ... because the "loss" is way in the future... in the form of extra wear & tear, and a shorter vehicle life/reduced residual car value.
And of course that depreciation WILL vary -- it's far worse for newer cars, because in the first year or two (or even 3) of a vehicle's lifespan, the depreciation is substantial, almost regardless of the mileage -- but once you get past year 3, the mileage DOES start to matter; moreover the probability of needing major repairs increases as well.
Consider that a person who puts < 10,000 miles per year on a particular vehicle can probably get 10+ years out of it, and thus reduce the total number of vehicles owned over a lifetime. By contrast, the person who puts > 15,000 or upwards from 20,000 miles per year on a vehicle, will likely get (at most) 5 to 6 years (and possibly less) before trading it in/buying a different vehicle.
It should be obvious that cumulatively (over one's whole lifetime) the latter person will go through probably (at least) two times as many vehicles, and thus will lose substantially more in depreciation.
Nor is that loss strictly a LINEAR calculation; instead it tends to be a reverse exponential averaging around 15% to 25% per year (median of 20% per year) declining -- the first few years of owning any car (whether new OR used) will be, relatively speaking, the years of greatest loss of value (though of course in terms of total dollars, as well as percentages, the loss on "brand new" vehicles is substantially higher than on a vehicle that is already 3+ or 5+ years old at purchase).
And ironically -- if you purchase a vehicle at around 5 years of age -- and hold it/drive it for 10+ years (especially if you keep annual mileage down below average, AND you keep it maintained and "clean")... well around year 15 that trend actually starts to reverse, and the vehicle MAY begin to appreciate as a "classic" car -- and that is when TOTAL mileage really begins to matter.
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So, long story short yes, having a full conscious awareness of that "per month" and "per day" vehicle cost is important (and necessary for budgeting purposes) and necessary -- but for long term "spending control" and wealth accumulation, it really isn't sufficient; you also need to become consciously aware of the PER MILE cost, and factor that into your behavior & shopping patterns.
(Note: it takes a bit of discipline -- but I also find it "freeing" in that it makes me MUCH less susceptible to various "it's on sale" marketing pressures, and I engage in much more "conscious/conscientious" and planned purchase behaviors {sales are "serendipitous" then like a windfall, rather than something I rely on}.)
