M20C 25hr fuel burn

[tcal780]

Hi All,

After two months of ownership and 25 hours on the tach, I've calculated a net burn rate of 8.3 gal/hr. Most of my flying has been lower altitudes, lots of pattern work, maneuvers, and just getting familiar with it. I've been running 2300@23" or 24" and keep it on the rich side (probably 150 degrees below peak). I'm scared to run it too lean with my original gauges (1-CHT probe with a gauge indicating anywhere between 200 and 500 degrees, and the 1-4 EGT selector). This bird runs hot at Vy. Vx would redline it in a minute when it's 80+ degrees outside. Cruise, is solidly in the "green." I'll feel much better when I can get an EDM900 in there.

Anyway, I've included a pic of the spreadsheet I'm keeping to track the fuel usage. I'm pretty happy zooming along at 140kts burning 8.3 gal/hr. I guess I'm just surprised it wasn't more like 9-10, especially considering the type of flying I've been doing.

Anyone else with similar/dissimilar results on their M20C?

 

[Mooneymite]

Hmmmm.

That's unbelievably low.

Perhaps using flight time instead of tach time would yield more believable burn numbers?

Most airplanes get low burn numbers for ground operations, so averaging ground ops with flight time isn't accurate.....,

or your tach is running too fast.   

Most of us C owners are seeing closer to 9-10.

 

 

Edited July 8, 2022 by Mooneymite

[Oscar Avalle]

I agree this is extremely low.

Several issues.

Invest in an Engine monitor. Don’t rely on your OEM CHTs or EGTs. Our Cs run very Hot and CHTs tend to be high. Over the years I have been able to get them down to a more acceptable level but still I have to manage them carefully during each flight. In particular if OAT is high.

Fuel consumption, ROP my engine consumes around 9.6/hr at 73% power and LOP around 8.6 gal/hr. This provides me with around 138kts TAS at 6,000 feet. However to be on the safe side I calculate around 9.7 gal/hr for my fuel consumption. Keeping in mind taxi and climb consumption.

Enjoy your C and share pics

Oscar


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[chriscalandro]

That….doesn’t sound right. 

[Hank]

My C is usually right around 9 gph block time, using flight time from my watch not the tach [my watch is a larger number]. When nice and high, 9000+, I can achieve ~8.5 gph at 19-20" / 2500. I back off from full throttle just enough to make the MP needle wiggle, then leave it.

Down lower, mid-altitudes like you reported, I generally run 22" / 2400, and down low on a next-airport breakfast or lunch run, I'll use 23" / 2300.

The Key Number for our engines is MP + RPM/100 = 46, so just add the numbers from the MP gage and the tach, keep the sum equal to or less than 46 and stay out of the caution zones on your tach.

I can check my receipts at home for the last fillups when traveling, a mix of IFR/IMC and VFR, for comparison, all at 5000-8000'.

[tcal780]

Thanks for the feedback. I definitely have the engine monitor prioritized for next upgrade. Ill double check I didn't miss a top off somewhere in there.

[Floyd]

To get a true cruse fuel burn rate,  Top off a tank.  Take off on the other tank. Get to cruse altitude and power setting, switch to full tank, note the time.  At end of cruse, note the time and switch back to other tank.  Land and top the cruse tank and calculate the gal/hr.  Lots of variables for total flight.  Ground ops 1-2 gph.  Take off about 16.5 gph, climb and decent depends on power setting.

Have fun.

[carusoam]

The hard part…

Max FF during T/O and climb is about 2X cruise efficiency…

So…. Doing pattern work, there is a lot of Max FF blended in with low power/leaned efficiency….

 

I flew an M20C for a decade without an engine monitor… or FF instrument….

For best results… do all the T/O and climb on one tank, cruise efficiently on the other… fill the tanks with as much accuracy as possible… park the plane on the same level ground, in the same spot…

 

There are a lot of low cost, pre-flown engine monitors around here…. Get one.   Plan the next steps to minimize the installation cost….

Installing an engine monitor has a lot of wires… 

Installing a FF sensor is a challenging plumbing exercise….

Copy a good resource….

Book numbers are incredibly useful… keeping track of time and power settings can prove this out…

Go Mooney efficiency!

1k hrs from now… you will still be impressed at how well the M20C flys…!

Mine would fly 2X as fast as my Firebird and get the same mileage, with none of the traffic….   

 

Next steps… prove the T/O and climb performance match the book numbers as well…

Best regards,

-a-