Every gas charge from Monarch since July 2024, converted to estimated gallons with EIA's weekly San Francisco premium price. That takes out the 2026 price spike and the difference in tank size, so the cars compare on gallons per 30 days.
Gallons per 30 days
The Mini's two baselines are from before the Porsche (Feb 21 2026), when every fill was the Mini. The Volvo is measured fill to fill.
Porsche 997.2 Turbo S
Filled only on weekends. Since the Volvo arrived there's no Mini, so every Porsche fill is tagged directly. Before that, weekend fills could have been either car, so that period only has an upper bound.
Estimated gallons bought per month, by car
Weekend fills between the Porsche and the Volvo can't be split between the Mini and the Porsche, so they're shown separately.
Car washes, snacks and ChargePoint sessions are left out. The current month is partial.
What gas cost: EIA San Francisco premium, weekly
This is why dollars alone mislead: premium went from about $4.50 in January to over $6.70 by October.
Fuel means gas-category charges of $20 or more. Smaller ones are car washes, snacks or top-offs, and ChargePoint is EV charging (about $7 per 30 days so far).
Porsche: it's filled only on weekends, so weekend fills from Feb 21 to Aug 23 2026 are left out of the Mini numbers. The Mini baselines use the 12 months before the Porsche and the same season a year earlier. Since the Volvo arrived, weekend fills are tagged by car, and the Porsche's rate is gallons bought ÷ days since Aug 24.
Confirmed by Hassan on Oct 8 2026: Sep 13 (Half Moon Bay) and Sep 20 were the Porsche, Sep 16 was the Civic, and Sep 9 and Oct 8 were the Volvo.
Prices: EIA is an area average. The Menlo Park Chevron runs above it, so the Volvo's gallons are probably slightly overstated, which makes these numbers conservative.
Not included: home charging. A full charge costs about $5 at PG&E EV2-A off-peak, so charging most nights would cancel much of the gas saving. Office charging is free.
Updating: new fills are added from Monarch by hand. EIA prices refresh every week on their own.