Diamond DA42 Twin Star Cost of Ownership: Diesel Twin Budget, Engine Reserves and Loan Line
This is the annual budget for a Diamond DA42 Twin Star, built around the Austro AE300 diesel versions (DA42 NG and DA42-VI), with the avgas DA42 L360 and the early Thielert-powered airplanes compared along the way. It is written for an owner-pilot; flight schools will see higher utilization and commercial insurance.
Which DA42 are you budgeting for?
The DA42 is a four-seat composite twin with retractable gear, first delivered in 2004. Its engines define the budget more than any other choice, so identify them before you compare prices. Specs and generated payment examples are on the DA42 Twin Star model page.
| Version | Engines | Fuel | Budget notes |
|---|---|---|---|
| Early DA42 | Thielert TAE 125 (Centurion) diesels | Jet-A | Managed on a replacement-time basis rather than overhauled; confirm current limits and exchange pricing with Continental, which now supports the engine family. Some airframes have been converted, so read the logs. |
| DA42 NG / DA42-VI | Austro AE300, 168 hp each | Jet-A | FADEC diesels with an overhaul interval published by Austro (commonly cited at 1,800 hours; confirm for the serial numbers). This page's budget basis. |
| DA42 L360 | Lycoming IO-360, 180 hp each | 100LL | Conventional Lycoming maintenance and wide shop support; higher fuel burn. |
Prices are hedged. Our model data lists typical DA42 prices from about $280,000 for early airplanes to $650,000 for late ones, and values depend on the engine version, engine times and panel. Verify with Vref or Aircraft Bluebook and recent sold comparables. For a new DA42, contact Diamond or a dealer; we do not publish unverified list prices.
DA42 annual budget at 50, 100 and 200 hours
Fixed costs
| Item | Per year | Basis |
|---|---|---|
| Insurance (hull + liability) | $6,500 | Assumption for an experienced multi-engine pilot; not a quote |
| Hangar | $6,000 | Assumption ($500/month) for a twin-width hangar |
| Annual inspection (before squawks) | $5,000 | Assumption; Diamond service center, two FADEC engines |
| Avionics databases, subscriptions, misc. | $2,000 | G1000 databases, EFB, small parts |
| Total fixed | $19,500 |
Hourly operating costs
| Item | Per flight hour | Basis |
|---|---|---|
| Fuel (Jet-A) | $78.00 | 12 gph total × $6.50/gal (illustrative Jet-A price, not a verified average) |
| Oil and filters | $4.00 | Two engines; approved oils per Austro |
| Engine reserve (two engines) | $72.22 | Illustrative $65,000 per engine ÷ 1,800 hr |
| Propeller reserve (two props) | $8.00 | Constant-speed props spread over their overhaul interval |
| Unscheduled maintenance reserve | $40.00 | Sensors, gear, brakes, avionics, composite touch-ups |
| Total hourly | $202.22 |
Total by utilization
| Hours / yr | Operating cost | Per hour | With loan | Per hour with loan |
|---|---|---|---|---|
| 50 | $29,611 | $592 | $67,563 | $1,351 |
| 100 | $39,722 | $397 | $77,674 | $777 |
| 200 | $59,944 | $300 | $97,897 | $489 |
Every line is an assumption; replace it with quotes from a Diamond service center and your insurer. The engine reserve assumes $65,000 per engine over 1,800 hours. If your quote is $80,000, the two-engine reserve rises to $89 per hour. Low-utilization owners should also read understanding SMOH and TBO, because calendar limits and component life can arrive before hours do.
Jet-A vs 100LL: the DA42's fuel economics
The diesel DA42's appeal is fuel. Jet-A retail prices are not in our verified data and vary widely from one FBO to the next, so the table below shows a range of illustrative prices against an avgas DA42 L360 at the verified 100LL national average of $7.24 (AirNav, September 2026).
| Jet-A price (illustrative) | Diesel fuel per hour | Diesel fuel per 100 hours | Hourly saving vs L360 |
|---|---|---|---|
| $5.50 | $66 | $6,600 | $64 |
| $6.50 | $78 | $7,800 | $52 |
| $7.50 | $90 | $9,000 | $40 |
| $8.50 | $102 | $10,200 | $28 |
On these burn assumptions the diesel only loses on fuel if Jet-A costs more than about $10.86 a gallon. What you give up is the breadth of shop support: AE300 and Centurion work goes to Diamond- or engine-maker-qualified facilities, so factor travel and downtime into the budget if the nearest one is far away. For the single-engine version of this trade, see the DA40 NG cost of ownership.
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Insurance and pilot requirements
A DA42 needs a multi-engine rating, and its retractable gear and constant-speed props make it complex. We budget $6,500 a year as an assumption for an experienced multi-engine pilot. There is no DA42 premium benchmark in our verified sources; newly rated pilots should expect higher premiums or training conditions such as dual time in type. The insurance market was generally stable for experienced piston owners in 2026, according to BWI, but twins are priced individually. See insuring a financed aircraft.
How lenders look at a DA42 loan
As of September 2026, piston aircraft loan rates quoted by major aviation lenders generally start around 7% for well-qualified borrowers and run to roughly 10%. AOPA's multi-engine guidelines call for 15% to 30% down and maximum terms of 10 to 15 years, and its lenders prefer twins built in 1970 or later. At $420,000 with 20% down:
- 6.99% over 15 years: $3,018 a month
- 7.75% over 15 years: $3,163 a month
- 7.75% over 10 years: $4,032 a month
- 9.99% over 15 years: $3,609 a month
| Term | 6.99% APR | 7.75% APR | 9.99% APR |
|---|---|---|---|
| 10 years (120 mo) | $3,900/mo | $4,032/mo | $4,438/mo |
| 15 years (180 mo) | $3,018/mo | $3,163/mo | $3,609/mo |
Loan amount $336,000. Principal and interest only; excludes insurance, taxes and fees. Illustrative, not a quote.
Lenders will also ask about the engines: which version is installed, the time remaining to replacement or overhaul, and any open service bulletins. An engine program or recent exchange can support value. See aircraft loan requirements and how engine programs affect financing and resale.
How this page differs from related pages
This page is the DA42's annual budget. For the move into a DA42 from a single, see SR20 to DA42; for the step up to Diamond's larger twin, see DA42 to DA62. For other light-twin budgets, compare the Piper Seneca and the Beechcraft Duchess. Other aircraft are on the cost of ownership hub.
Frequently asked questions
How much does a Diamond DA42 cost to own per year?
On this page's planning assumptions, a diesel DA42 flown 100 hours a year costs about $39,722 to operate before financing, or $397 per hour. A loan on a $420,000 example (20% down, 7.75%, 15 years) adds about $37,952 a year. The engine reserve and the Jet-A price you actually pay are the biggest swing items.
How much fuel does a DA42 burn?
We plan on about 12 gallons per hour of Jet-A for both AE300 diesels combined, an assumption to check against your own power settings. At an illustrative $6.50 a gallon that is $78 per hour. Jet-A prices are not in our verified data and vary widely between FBOs, so substitute the price at your home field.
Is the diesel DA42 cheaper to fuel than the avgas DA42 L360?
Almost always. At an assumed 18 gph for two IO-360s and $7.24 per gallon of 100LL, the L360 spends about $130 an hour on fuel. The diesel at 12 gph only matches that if Jet-A costs about $10.86 a gallon. The diesel's trade-off is engine support: plan maintenance around a Diamond or Austro-qualified shop.
What engines are in a DA42 and how are they maintained?
Early DA42s used Thielert TAE 125 (Centurion) diesels, which are managed on a replacement-time basis rather than overhauled; Continental now supports that engine family. Later DA42 NG and DA42-VI models use the 168 hp Austro AE300, and the DA42 L360 uses 180 hp Lycoming IO-360s on 100LL. Confirm the installed engines and their limits in the logs before you budget.
How much down payment and what term for a DA42 loan?
AOPA's guidelines call for 15% to 30% down on multi-engine aircraft, with maximum terms of 10 to 15 years, and its lenders prefer twins built in 1970 or later, which every DA42 is. On a $420,000 example with 20% down, the $336,000 loan is about $3,163 a month over 15 years at 7.75%, or $4,032 over 10 years.
Is a DA42 expensive to insure?
It depends heavily on multi-engine experience. We budget $6,500 a year as an assumption for an experienced multi-engine pilot, but newly rated pilots can pay much more or be required to complete type-specific training and dual time first. There is no DA42 benchmark in our verified sources, so get a quote with your logbook totals before you make an offer.