An hour a day, priced
Fifty-five minutes a day over 250 working days is 229.2 engine hours. At 0.6 gallons an hour that is 137.5 gallons and, at $3.72, $511.50 a year for one vehicle — $2,046 across four. Expressed the other way round, that fuel would have carried the van 2,269 miles at 16.5 mpg, which is roughly a month and a half of its normal running.
None of it appears anywhere as a line item. There is no idling invoice. It arrives mixed into the ordinary fuel spend, and the only trace it leaves is an economy figure that is worse than the vehicle deserves.
The economy figure lies about the vehicle
Divide 18,000 road miles by the 1,228.4 gallons the van actually bought — road fuel plus idle fuel — and the answer is 14.7 mpg. The van does 16.5. Nothing about the driving explains the difference and nothing about the driving can fix it, because 11.2 per cent of the fuel went into standing still.
This is worth knowing before ranking vehicles on a fuel report. The vans with a lift, a compressor or a refrigeration unit will always sit at the bottom of that list, and they will sit there for a reason that has nothing to do with who is driving them. If you are going to compare, compare road fuel to road miles and account for the standing time separately.
Engine hours are not free miles
The last section uses a number from your own maintenance policy: how many miles of wear your shop counts for each engine hour. On the defaults that is 30, so 229.2 idle hours add 6,875 equivalent miles, which against a 7,500 mile interval is 0.92 of an extra service a year — one more service roughly every thirteen months.
Whether that conversion is 20, 30 or 40 is a question for whoever specifies your servicing, and it is deliberately an input here rather than a constant. What is not in doubt is the direction: a vehicle scheduled purely on odometer readings reaches each service later than its engine has earned it, and heavy idling widens that gap every year.
Related pages
Fuel card reconciliation is the period-by-period version and treats idle fuel as the reason a mileage-only check misreads. Fuel cost handles the moving side, generator fuel runtime does the same burn-rate arithmetic for standalone engines, and cost per mile puts the whole vehicle on a per-mile footing.
Questions people ask
What gallons-per-hour figure should I use?
One for your own vehicle in the mode it actually idles in, and the two are often very different numbers. A bare engine at idle is one thing; the same engine driving a lift, a compressor, a refrigeration unit or a power take-off is doing real work and burns accordingly. If you have telematics that report fuel rate, take it from there. If not, the crude version is to note the fuel level, leave it running for an hour in the mode you care about, and note it again.
Why does idling make the fuel card economy look bad?
Because the card knows every gallon and the odometer knows every mile, and idle fuel appears in one and not the other. On the default figures the vehicle does 16.5 mpg on the road and reports 14.7, purely because 11.2 per cent of its fuel went into standing still. The size of that distortion scales directly with idle time, which is why vehicles running equipment off the engine always look worst on a report that does not separate the two.
Is all idling waste?
No, and treating it that way produces bad decisions. A refrigeration unit protecting a load, a lift raising a pallet, a cab kept survivable in extreme weather and an engine at temperature before it is worked are all doing something. What the page gives you is the price of that time so you can tell the useful hours from the ones nobody chose — the twenty minutes waiting at a gate with the engine on is a different line from the hour running a compressor, and only one of them is a candidate for changing.
Should I count idling toward service intervals?
That is a decision for whoever specifies your maintenance, which is why the conversion figure is an input rather than a constant here. The reason it comes up at all is that an hour of running loads an engine while adding no miles, so a schedule based purely on the odometer arrives late for a vehicle that idles heavily. Take the miles-per-engine-hour figure from your shop or your own policy and use it consistently rather than switching it to suit an answer.
Are there rules about how long a vehicle can idle?
Where you operate may well restrict it, and this page does not know and does not assert anything about that. Restrictions are set locally, they differ between neighbouring places, and they change. If it matters for your work, ask the authority that would enforce it rather than taking a figure from any calculator. The separate and more immediate issue is that an engine running in an enclosed space is a carbon monoxide hazard, which is a site and ventilation question, not an arithmetic one.