Diamond DA40 NG Cost of Ownership: Jet-A vs 100LL Economics and the AE300 Engine
The DA40 NG is the diesel Diamond DA40, powered by an Austro Engine AE300 that burns Jet-A. This page is for owners and buyers who want to know whether Jet-A actually saves money over 100LL, how to reserve for the AE300, and what the whole annual budget looks like.
What is the DA40 NG, in cost terms?
The NG keeps the four-seat, fixed-gear composite DA40 airframe and replaces the Lycoming IO-360 with the Austro AE300, a turbocharged, liquid-cooled diesel of about 165–168 hp with single-lever FADEC control. It was EASA-certified in April 2010. FLYING's flight review reported 8.2 gph at maximum continuous power and about 150 knots true, and 5.1 gph at about 126 knots in economy cruise, with about 39 gallons of usable fuel in the airplane tested. Like the DA40-180, it is not a complex airplane and needs no high-performance endorsement.
For the buying decision (variants, inspection, service-center access), see the Diamond DA40 buyer's guide. For the avgas DA40's own budget and composite-airframe notes, see Diamond DA40-180 cost of ownership.
Jet-A vs 100LL: the break-even formula
Fuel cost per hour is simply gallons per hour × price per gallon. The NG saves money on fuel when:
NG gph × Jet-A price < DA40-180 gph × 100LL price
Rearranged, the break-even Jet-A price = DA40-180 gph × 100LL price ÷ NG gph. Using 8.5 gph for the DA40-180 (our aircraft database) and $7.24 for 100LL (AirNav national average, September 2026):
| How you fly the NG | Break-even Jet-A price per gallon |
|---|---|
| Economy cruise (5.1 gph, about 126 KTAS) | $12.07 |
| Planning cruise (6.5 gph, assumption) | $9.47 |
| Max continuous (8.2 gph, about 150 KTAS) | $7.50 |
The comparison is sensitive to power setting. Flown fast, the NG burns nearly as much fuel by volume as the avgas DA40, and the advantage then depends on Jet-A being cheaper than 100LL at your airport. Retail Jet-A at full-service FBOs is priced for turbine customers and can be close to, or even above, 100LL, so check actual prices along your routes on AirNav.
What the difference is worth per year
The Jet-A prices below are illustrative inputs, not market data. Each row compares the NG at 6.5 gph with a DA40-180 at 8.5 gph and $7.24 100LL.
| Assumed Jet-A price | NG fuel / hr | DA40-180 fuel / hr | NG saves / hr | Per year at 100 hr | Per year at 200 hr |
|---|---|---|---|---|---|
| $5.50 | $36 | $62 | $26 | $2,579 | $5,158 |
| $6.50 | $42 | $62 | $19 | $1,929 | $3,858 |
| $7.50 | $49 | $62 | $13 | $1,279 | $2,558 |
| $8.50 | $55 | $62 | $6 | $629 | $1,258 |
For your own numbers, try the fuel cost calculator with each fuel's burn and local price.
The AE300 engine: TBO and replacement budgeting
Austro Engine's AE300 received EASA approval for a 1,800-hour TBO in 2015, up from 1,500 hours. FLYING's review noted that, unlike the earlier Thielert diesels, which had to be replaced, the AE300 can be overhauled, and reported no separate reduction-gearbox inspections under the then-current TBO. Whether the interval is a hard limit for a privately operated U.S. airplane depends on how it appears in the engine's instructions for continued airworthiness and the airplane's limitations. Confirm with a Diamond service center, and budget as if it is.
Overhaul and exchange pricing for the AE300 is not in our verified sources, so the reserve is a formula: quote ÷ 1,800 hours. At illustrative quotes:
| Illustrative AE300 overhaul/exchange quote | Reserve per hour | vs IO-360 reserve |
|---|---|---|
| $50,000 | $27.78 | +$5.28/hr |
| $65,000 | $36.11 | +$13.61/hr |
| $80,000 | $44.44 | +$21.94/hr |
The shorter interval matters: over the same 1,800 hours, a DA40-180's IO-360 has used only 90% of its 2,000-hour TBO. Get a real quote before you buy, ask what the exchange program includes, and check the engine's hours and calendar status in the logs. See understanding SMOH and TBO.
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DA40 NG annual budget at 50, 100 and 200 hours
Fixed costs
| Item | Per year | Basis |
|---|---|---|
| Insurance (hull + liability) | $2,800 | Assumption; higher hull value than an older DA40-180 |
| Hangar | $4,800 | Assumption ($400/month) |
| Routine annual inspection | $3,000 | Assumption before squawks; Diamond service center familiar with the AE300 |
| Avionics databases, subscriptions, misc. | $1,500 | Garmin database updates, EFB, small parts |
| Total fixed | $12,100 |
Hourly operating costs
| Item | Per flight hour | Basis |
|---|---|---|
| Fuel (Jet-A) | $42.25 | 6.5 gph × $6.50/gal (illustrative Jet-A price, not a verified average) |
| Oil and filters | $3.00 | Approved oils for the AE300; confirm with your service center |
| Engine reserve | $36.11 | Illustrative $65,000 overhaul/exchange ÷ 1,800 hr TBO |
| Propeller reserve | $4.00 | Constant-speed prop overhaul spread over its interval |
| Unscheduled maintenance reserve | $20.00 | Avionics, brakes, tires, sensors, composite touch-ups |
| Total hourly | $105.36 |
Total by utilization
| Hours / yr | Operating cost | Per hour | With loan | Per hour with loan |
|---|---|---|---|---|
| 50 | $17,368 | $347 | $55,050 | $1,101 |
| 100 | $22,636 | $226 | $60,318 | $603 |
| 200 | $33,172 | $166 | $70,854 | $354 |
Every input is an assumption. The two that matter most, the Jet-A price and the AE300 overhaul quote, are not in our verified data, so replace them first. See hangar vs tie-down costs and annual inspection costs for the fixed lines.
The unleaded-avgas transition: why diesel owners watch from the sidelines
For 100LL airplanes, the lead phase-out is a live cost question. EAGLE's stated goal is to eliminate leaded avgas for piston aircraft by the end of 2030 (2032 in Alaska); the FAA's July 2026 transition plan found a universal drop-in replacement "not feasible" and says the timeline could extend past 2030. About 212 airports offered some unleaded option as of August 2026, and unleaded fuels are still working toward fleet-wide approval and distribution.
The NG sidesteps that uncertainty because it burns jet fuel. The trade-offs are that Jet-A is not sold at every small airport, and its FBO price is set for turbine traffic. Whether diesel DA40s gain a resale premium as the transition unfolds is not something current data shows, so don't pay extra for the airplane on that assumption. See what the unleaded transition means for piston costs and values.
Buying price, the loan line and the premium over a DA40-180
Diamond does not publish list prices, and we have no verified market data for the NG. Asking prices seen in 2025–2026 listings span very roughly $350,000 to $650,000 by year, hours and options, so the budget uses an illustrative $450,000. Verify any airplane with Vref or Aircraft Bluebook. With 15% down, the $382,500 loan over 20 years costs about $2,963 a month at 6.99%, $3,140 at 7.75% and $3,689 at 9.99%.
Against a DA40-180 at the database mid price of $200,000, the NG's hourly operating cost on these assumptions is about $2.18 lower, while the larger loan costs about $20,934 more a year. Fuel savings do not recover that premium. What the premium buys is a newer airframe and panel, single-lever FADEC operation and independence from 100LL. Those are good reasons to buy an NG; cheaper flying is not. For the step to Diamond's larger single, see the DA40 to DA50 upgrade guide, and for lender expectations see aircraft loan requirements.
How this page differs from related Diamond pages
This page covers the DA40 NG's annual budget and its Jet-A economics. The avgas DA40's budget, composite-inspection notes and resale drivers are on Diamond DA40-180 cost of ownership. The buying decision is in the Diamond DA40 buyer's guide, and specs with generated payment examples for the Lycoming version are on the DA40-180 model page. Other aircraft are on the cost of ownership hub.
Frequently asked questions
Is Jet-A cheaper to run than 100LL in a DA40?
It depends on the local Jet-A price and your power setting. The break-even formula is: DA40-180 gallons per hour × 100LL price ÷ DA40 NG gallons per hour. At 8.5 gph for the DA40-180, $7.24 100LL and 6.5 gph for the NG, the NG costs less in fuel whenever Jet-A is below about $9.47 a gallon. Flown at max continuous power, the break-even falls to about $7.50.
What is the TBO of the Austro AE300 engine?
Austro Engine raised the AE300 TBO from 1,500 to 1,800 hours in 2015 under EASA approval, and FLYING reported that the AE300 can be overhauled, unlike the earlier Thielert diesels, which had to be replaced. Confirm the current interval, any calendar limit and whether it is mandatory for your operation with a Diamond service center, and budget as if it is.
How much fuel does a DA40 NG burn?
FLYING's flight review reported 8.2 gph at maximum continuous power and about 150 knots true, and 5.1 gph at about 126 knots in economy cruise. We use 6.5 gph as a mixed-cruise planning figure. The NG burns Jet-A, so its fuel cost follows the local Jet-A price rather than 100LL.
Does the unleaded avgas transition affect the DA40 NG?
Not directly. The AE300 is a compression-ignition engine that burns jet fuel, so the move away from leaded 100LL, targeted by the EAGLE initiative for the end of 2030 but acknowledged by the FAA as possibly slipping, does not change its fuel. The practical questions for NG owners are Jet-A availability at small airports and the price FBOs charge for it.
How much does a used DA40 NG cost?
Diamond does not publish list prices, and we do not have verified market data for the NG. Asking prices seen in 2025–2026 listings span a wide range, very roughly $350,000 to $650,000 depending on year, hours and options. Verify any specific airplane with Vref or Aircraft Bluebook and a pre-buy at a Diamond service center.
Do the fuel savings pay for a DA40 NG over a DA40-180?
Not on fuel alone. On this page's assumptions the NG's hourly operating cost is only $2 lower than a DA40-180's, because the diesel's engine reserve offsets much of its fuel saving, while financing an illustrative $450,000 NG instead of a $200,000 DA40-180 adds about $20,934 a year in loan payments. The premium buys a newer airplane, not cheaper flying.