Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Net annual savings switching to mogas
$1,560
Gross fuel savings before extra costs
$1,760
Annual gallons burned
800
Net savings per flight hour
$15.60
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter hours flown per year.
- 2Enter fuel burn (gal/hr).
- 3Enter 100ll price ($/gal).
- 4Enter ethanol-free mogas price ($/gal).
- 5Enter extra hauling/storage cost per year ($).
- 6Read your net annual savings switching to mogas on the right — it updates as you type.
- 7Hit Share to keep the scenario or send it to someone.
About this calculator
Automotive gas (mogas) with an ethanol-free STC often runs $1.50-3.00/gallon cheaper than 100LL avgas at airports that offer it, but not every engine is approved and not every airport sells it, so you often need to truck fuel in or drive to a self-serve pump. This calculator nets the per-gallon savings against your annual fuel burn to show real annual savings, while flagging that mogas isn't a free lunch — it typically has a shorter usable shelf life and stricter octane and ethanol-content requirements than 100LL.
Worked example
Using the values the calculator loads with:
Inputs
- Hours flown per year: 100
- Fuel burn: 8 gal/hr
- 100LL price: 6.3 $/gal
- Ethanol-free mogas price: 4.1 $/gal
- Extra hauling/storage cost per year: 200 $
Results
- Net annual savings switching to mogas: $1,560
- Gross fuel savings before extra costs: $1,760
- Annual gallons burned: 800
- Net savings per flight hour: $15.60
What each field means
Inputs
- Hours flown per year
- The hours flown per year used in the calculation. Starts at 100 so you have a working example on load.
- Fuel burn (gal/hr)
- The fuel burn used in the calculation, measured in gal/hr. Starts at 8 gal/hr so you have a working example on load.
- 100LL price ($/gal)
- The 100ll price used in the calculation, measured in $/gal. Starts at 6.3 $/gal so you have a working example on load.
- Ethanol-free mogas price ($/gal)
- The ethanol-free mogas price used in the calculation, measured in $/gal. Starts at 4.1 $/gal so you have a working example on load.
- Extra hauling/storage cost per year ($)
- The extra hauling/storage cost per year used in the calculation, measured in $. Starts at 200 $ so you have a working example on load.
Results
- Net annual savings switching to mogas
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Gross fuel savings before extra costs
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Annual gallons burned
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Net savings per flight hour
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Does every engine qualify for a mogas STC?
No — STCs from companies like Petersen Aviation and EAA typically cover specific low-compression engines like the Continental O-200 and certain Lycoming O-320/O-360 variants at lower compression ratios, but higher-compression, turbocharged, or fuel-injected engines are frequently excluded. Confirm your exact engine and airframe combination is on the STC's approved model list before assuming eligibility.
Why does mogas need to be ethanol-free specifically?
Ethanol absorbs atmospheric moisture and can cause phase separation in the tank, is more corrosive to certain fuel system seals and components not designed for it, and generally isn't approved under aviation mogas STCs. E0 (zero-ethanol) premium unleaded is the fuel that must be sourced, which is less commonly available at retail pumps than E10.
What's the shelf-life tradeoff?
Mogas typically degrades faster than 100LL, especially once exposed to air and temperature swings in a partially-filled tank, with some guidance suggesting use within 60-90 days versus 100LL's longer stable shelf life. Aircraft that sit for weeks between flights are poor candidates for mogas since stale fuel raises its own set of engine problems.
Is trucking mogas to the airport worth the hassle?
If your airport doesn't sell mogas on the field, you're hauling fuel in cans or a fuel trailer, which adds real labor time and a small safety/spill risk that some pilots decide isn't worth the savings, especially at low annual hours where total savings might only be a few hundred dollars. High-hour flyers at airports without on-field mogas still often find it worthwhile.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Avgas vs Mogas Savings Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/avgas-vs-mogas-savings
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/avgas-vs-mogas-savings" target="_blank" rel="noopener">Avgas vs Mogas Savings Calculator — RevenueLab</a> (2026).</p>
Source: [Avgas vs Mogas Savings Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/avgas-vs-mogas-savings) (2026).