310 / 320 economical Fuel Burn…

Home 2024 Forums Opening Section Buying a Twin Cessna 310 / 320 economical Fuel Burn…

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    I am looking toward the future..

    Currently have a partnership in a A36T, but really want something of my own. Plane will be for 80% business, 300-800 nm trips. I’m on the West Coast. The Bo is nice, but I feel cramped – and I hate that steering bar blocking the panel(!). I really like the cabin size of the 310, larger panel, and an extra engine when I’m coming home at night solo would be nice. The one or two I’ve sat in, just had a very nice “feel” to them.

    I’m a high time, ATP. Former Navy Intructor with time in C-130s and King Airs, and flew for a major airline awhile back (furloughed).

    I’ve been looking / researching for over a year, and keep coming back to the 310/320. The biggest negative factor is fuel burn. I don’t think fuel will be getting cheaper anytime soon. Anything more than abt 23 gph may be a deal-killer. I don’t have to go 200+ kts. Older (pre “Q” models) might be considered. Going slower (160-170ish instead of 190-200 kts) in a larger comfortable A/C to save fuel would be fine.

    What are real burn rates / speeds for these A/C in the 65% or even 55% power settings?
    I have not ruled out Turbo’d airplanes, and am not afraid to fly high to save fuel.

    Please post your real-world experience and burn numbers.


    Nice to see some interest in the 300 series πŸ™‚ I had mine listed in TAP for 6 mos. through this past summer. Got several calls from brokers and only two from, well, “tire kickers”.

    First, to answer your question, I run ROP, best power mixture. I don’t have GAMI’s, but do have EGT on all 12 cyls. I usually set 100-120 deg rich on the first-to-peak cyl. (Please, not to start the LOP/ROP debate again, folks, I have my reasons for operating this way). I see, at 61% power (2350 RPM/25 inches), 173-180 KTAS, depending on density altitude. Fuel for an entire flight profile runs close to 30 gph, 15 a side. Our T-Day trip to north WI totalled 12.4 flight hours (start to shutdown, 4 legs), for 379.4 gl. Or 30.596 gph. TAS at 15,000 on the easbound legs was about 180, at 61% power. Westbound, at 10,000 against the headwind, we saw 185 KTAS running 68% power for most of the last leg. Actual fuel burn for that leg worked out to 31 gph.

    FWIW, book numbers show, at 55% power (2350 RPM and 23″), 169 KTAS and 28 gph best power or 26 gph at Cessna’s “recommended lean” setting, which I think is peak EGT.

    <EDIT: I was wrong. Recommended Lean, according to my book, is 50 deg ROP at settings below 75% power. Operation at peak EGT is specifically “not authorized” and operating leaner than 50 deg rich is “not approved”. But as we all know, it’s an “old” book.>

    That 28 number I’ve seen in actual experience. If you were to set up for LOP operation, (GAMI’s, instrumentation), you’ll burn less.

    Yes, I get “respect” at the fuel pump and I’m usually offered the courtesy car before I’m out of the seat. 8) But, having owned several non-turbo singles, I sure like the added capability of two motors, etc. Lucky for me, my “Better Half” loves it and it was paid for before I retired.

    Hope this helps!

    ps Mine are TSIO-520-NBcEB RAM 1 (300hp for takeoff)


    If you get into a pre “R” model with the 260 HP engines, you should be able to get into the ballpark fuel burn.


      You might even consider the C303, it is Turbo-charged but only to 32.5″ so, it’s kinda like being turbo-normalized. We are seeing 24gph(total) at 165-170 KTAS and it doesn’t have the electromechanical gear, tip tanks/aux tanks, fuel switching/management, no critical engine and exhaust AD’s like the 310/320/401…Also, it has a 2000hr TBO for the de-rated 250hp L/TSIO-520AE counter rotating engines. We have owned ours for a year now and after the initial catch up annual, it is performing well and is very safe…


      With a Colemill Executive 600 310N (300 HP IO-520s) we were getting 175 KTAS @ 25 GPH combined using stock injectors. I’ve gotten it down to 168 @ 20 all the way up at 13k ft, but don’t do it often. With stock 470s, I’d expect it to be a hair more efficient, but I sure do like that extra power for takeoff, climb, and OEI safety. We run pseudo LOP.

      The new engines will have GAMIs, and I’m guessing they’ll do a bit better.

      You won’t be disappointed with a 310.


      My experience in our normally aspirated 310R is very similar to RCLOVER and his T310Q. I flight plan for 28 gph running 100 degrees ROP. I typically fly between 9,000′ – 11,000′ msl at a TAS of 180 kts. I can get her down to 26 gph at 170 kts at altitude once again running 100 degrees ROP. My engines are happy being run this way and if they’re happy, I’m happy. From an overall cost perspective in any medium twin a couple of gallons an hour is a nit.
      We couldn’t be happier with our 310. πŸ˜€


      Since you mentioned the 320 as a possible option, I assume you are not against an early 300 series Cessna. My 56 310 has been delivering just the kind of speed versus fuel burn you are targeting. Mine easily lays down 165 to 168 knots true while consuming fuel at a block rate of under your 23 GPH cap.

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