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mile for mile

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prkaye

Well Known Member
Question - mile for mile, how does flying an RV (say a 9, with a 150hp engine) cross country compare in fuel cost to driving a mid-size car? Assume no wind, average conditons, the RV following the same straight road as the car, the car doing normal highway speeds with no traffic.
Assume today's fuel prices.
 
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prkaye said:
Question - mile for mile, how does flying an RV (say a 9, with a 150hp engine) cross country compare in fuel cost to driving a mid-size car? Assume no wind, average conditons, the RV following the same straight road as the car, the car doing normal highway speeds with no traffic.
Assume today's fuel prices.
Click to expand...

My RV in econ cruise (what I normally use) gets about 25 mpg at altitude. 184 mph. My car gets 26 mpg.

Avgas costs about $1.15/gal more than auto gas where I live, so fuel costs are a about 25% more expensive than driving. 500% more fun to fly...

Of course, for many long trips a 'straight road' from start to destination doesn't really exist. :cool:
 
one example data point

My parents live 518 miles away by car, 356 by RV.

I get about 28 mpg highway in my car so it takes me 18.5 gallons to get there = $53.65 one way. (Gas around here is $2.90.)

Assume 10gph in an average RV and 150 KTAS. That's 2.37 hours = 23.7 gallons. Assume $4.00/gall 100LL (and that's low probably). $94.9 each way in 100LL.

I don't think you'll ever get better mpg economy out of an RV unless the road is really indirect. So it costs an extra $100 round trip (not counting insurance, hangar, oil changes, etc for either vehicle). I can drive 8 hours through the Metroplex or fly for a little over 2. No contest. :D
 
Yeah, but in Texas, we drive trucks!

Round trip to Minneapolis from Houston:

by RV - 11 hours total @ 8.8 gph = 96.8 gallons at $3.50/gallon = $338.80

by F150 pickup - 2500 miles @ 15 mpg = 166 gallons at $3.00/gallon = $498

......give or take ten or twenty cents a gallon. Oh, and the drive is 19 hours each way! :p


Your mileage will most assuredly vary! :D

Paul
 
KC09 Morris, IL - KVTA Newark, OH

2 hours or less by RV = 9.1GPH X $4.00 gallon -- $145.60 round trip

6 hours by SUV (852 miles) = 18mpg X $3.00 gallon -- $142.00 round trip


Time is priceless - I can go see my sister and return in the same day ... you can't do that by car.
 
Car-equivalent MPG

Brian130 said:
Gas around here is $2.90. ... Assume 10gph in an average RV and 150 KTAS...Assume $4.00/gall 100LL (and that's low probably)
Click to expand...

Ok, so here's how I would calculate a "car-equivalent MPG". I changed the GPH figure to 8, because as others have pointed out, 10 seems a little high:

[Cruise speed, kts]*[1.15 mph/kts]/[GPH]*[Cost of 87 octane]/[Cost of 100LL]

= 150*1.15/8*2.90/4.00

= 15.63 car-equivalent mpg for the RV

Now, if you factor in the difference between driving on a curvy road vs as-the-crow flying, the value gets a little more reasonable

= 15.63/0.80
= 19.54

Finally, let's add the cost of slower driving to the cost of the car, assuming time is worth $50/hr and the car gets 27 mpg:

Cost of Car Gas = [Cost of 87 Octane]
+ (1/[driving speed] - 1/[flying speed])*[hourly rate]*[MPG of car]

= 2.90 + (1/75 - 1/173)*50*27
= $13.10 per gallon!

So if we factor that into our original calculation, we get a much different result:

= 150*1.15/8*13.10/4.00/0.8
= 88.3 car-equivalent mpg!
 
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Brian130 said:
My parents live 518 miles away by car, 356 by RV.

I get about 28 mpg highway in my car so it takes me 18.5 gallons to get there = $53.65 one way. (Gas around here is $2.90.)

Assume 10gph in an average RV and 150 KTAS. That's 2.37 hours = 23.7 gallons. Assume $4.00/gall 100LL (and that's low probably). $94.9 each way in 100LL.
Click to expand...
Those numbers don't look quite right. If the "356 by RV" is statute miles, you forgot to convert sm to nm, which would make the RV trip 2.1 hours, 21 gallons, and $84. Still more. Darn it. You just need to get more of a gas-guzzling car. :)
 
Osh to Atl 3.4hours 35 gallons, $140 by RV-8

Osh to atl by car 17hours, 37 gallons, $111 dollars

Car wins fuel cost. ~26% more costly to fly RV.
Oh well.
Best,
 
Seems to me the following somehow need to be figured in:

Cruise ground speed- power setting, fuel/air mixture
Some allowance for time saved (quality of companions...)
Head/tail winds
Weather limitations, diversions
Type of fuel used (big advantage to mogas)
Hanger/storage fees
Fun factor- who really wants to drive anyway??? :D
 
PRKAYE brings up an interesting point

How does the gph of a 118hp compare to a 160hp lycoming?

Now that is an interesting idea (especially since I am building a RV9-A with the Lycoming o235 L2C 118 hp engine with a Catto two bladed prop).

Extrapolating Van's numbers for the 118 hp engine (and checking the Lycoming Engine Manual) we get an estimation that follows:

Full power 173 mph 4.53 flight hrs 7.5 gal/hr
(assuming 34 gal. usable..start/taxi/takeoff...)
75% power 166 mph 5.27 flight hrs 6.45 gal/hr
55% power 150 mph 6.90 flight hrs 4.92 gal/hr

I drive from Ozark, MO to Wichita, KS often. 257 miles 4 hours 15 minutes and get barely over 20 mpg with my Jeep Grand Cherokee for a total fuel consumption of 12.85 gal at $2.89 per gal equals $37.14

Lets use full power RV9-A (using AeroPlanner.com)
full power 229 sm 173 mph 1.32 flight hrs 11.9 gal used (2 gal. for start/taxi/takeoff/altitude @6000 ft.)
75% power 166 mph 1.38 flight hrs 10.9 gal used
55% power 150 mph 1.53 flight hrs 9.5 gal used
Assuming 100LL is $4 per gal........
Full power would cost $47.60 :eek:
75% $43.60 :)
55% $38.00 :D

The 0235 118 hp engine isn't looking so bad after all. Of course, only true flight will tell us how close the extrapolated numbers really come but it is an interesting exercise with fuel prices rising. I can't wait to get this bird in the air.
Pat Garboden
Ozark, MO
RV9-A 942WG (reserved) 0235 L2C 118 hp
RV9-A 942 PT (reserved) 0320 E2A 150 hp
 
10 gph?

Brian130 said:
Assume 10gph in an average RV and 150 KTAS. That's 2.37 hours = 23.7 gallons. Assume $4.00/gall 100LL (and that's low probably). $94.9 each way in 100LL.

. :D
Click to expand...

10 gph to do 150 knots in an RV is way on the high side! On long trips my 9A will easily do 8gph running it hard, and at higher altitudes the block times (fuel burns for a given trip including take off, climb, cruise, decent) will come out right at 7gph with speeds around 157-160 knots. About 2 months ago my wife and I flew from San Jose, CA to Oklahoma for our sons basic training graduation and made several stops. Six weeks later we duplicated the trip to bring him his car with the final destination in Northern Texas about 40 miles from the Oklahoma location. On both trips we overnighted at Laughlin, except the RV got us there in about 3 hours burning just under 21 gallons. The same leg took 8 hours by Cobra Mustang and used 23 gallons. The rest of the trip was similar.

While a smaller engine seems like it should burn less gas we repeatedly are reminded that the planes running the bigger engines powered back do as well or better. The injected 200hp RV's running LOP seem to use the least amount of fuel in any group when flying together. Just another opinion, but go with the biggest engine that can be used for your plane. I'd be prepared to spring for a coke if your not happy after a year or so.

Regards,
 
Funny you were running these numbers because I was doing the same over the weekend only I was comparing my O-290 powered RV-9 to Corey Bird's 240 knot Symmetry.

Lots of SWAGS were used but here is what I came up with.

RV-9 w/ O-290-D2
75% power = 101.5 HP
7.1 GPH
175 MPH
24.6 GPM
200 mile trip = 1:10 minutes +/-
1:10 minutes * 7.1 GPH = 8.1 gallons * $4 = $32.46

Symmetry w/ IO-360
75% Power = 150 HP
12 GPH (I'm guessing here)
240 knots / 276 MPH
23 MPH
200 mile trip = 45 minutes +/-
45 minutes * 12 GPH = 8.7 gallons * $4 = 34.78


gorbak said:
How does the gph of a 118hp compare to a 160hp lycoming?

Now that is an interesting idea (especially since I am building a RV9-A with the Lycoming o235 L2C 118 hp engine with a Catto two bladed prop).

Extrapolating Van's numbers for the 118 hp engine (and checking the Lycoming Engine Manual) we get an estimation that follows:

Full power 173 mph 4.53 flight hrs 7.5 gal/hr
(assuming 34 gal. usable..start/taxi/takeoff...)
75% power 166 mph 5.27 flight hrs 6.45 gal/hr
55% power 150 mph 6.90 flight hrs 4.92 gal/hr

I drive from Ozark, MO to Wichita, KS often. 257 miles 4 hours 15 minutes and get barely over 20 mpg with my Jeep Grand Cherokee for a total fuel consumption of 12.85 gal at $2.89 per gal equals $37.14

Lets use full power RV9-A (using AeroPlanner.com)
full power 229 sm 173 mph 1.32 flight hrs 11.9 gal used (2 gal. for start/taxi/takeoff/altitude @6000 ft.)
75% power 166 mph 1.38 flight hrs 10.9 gal used
55% power 150 mph 1.53 flight hrs 9.5 gal used
Assuming 100LL is $4 per gal........
Full power would cost $47.60 :eek:
75% $43.60 :)
55% $38.00 :D

The 0235 118 hp engine isn't looking so bad after all. Of course, only true flight will tell us how close the extrapolated numbers really come but it is an interesting exercise with fuel prices rising. I can't wait to get this bird in the air.
Pat Garboden
Ozark, MO
RV9-A 942WG (reserved) 0235 L2C 118 hp
RV9-A 942 PT (reserved) 0320 E2A 150 hp
Click to expand...
 
mpg

I have an RV-9A and an O-320 fixed pitch prop rated at 160 hp. At 8000 feet and 75% I get 185 mph true and 21 mpg. At 55% I get 165 mph and 25 mpg. At 65 mph, my S-10 Blazer gets 21 mpg. At $3/gal, the car get 7 miles/$. At $4/gal, the airplane gets 5-6 miles/$. The 118hp at 75% is about the same as the 160hp at 55%.

Tom Green had a nice write-up in the recent RVAtor on the relative costs of bicycle, car, and RV. Tom used 175 mph and 22 mpg for the RV. Meals, motels, time on the road are all factors. Speeding tickets, insurance, hangar rent, etc. Of course, I spend about $2k a month to garage my car, but my wife and I stay free in the house. Regards, John.
 
When the CFO isn't looking

Dayton, Ohio to Fond Du Lac, WI via Sterling Rock Falls and Rockford, Illinois ~483 statute miles, 45.7 gallons 100LL, ~2.5 hrs, $178.23 (@ $3.90/gal), O-360-A1A. Driving not an option.

Bob Axsom
 
I've flown round trip from Minneapolis to Fort Myers FL about 5 times in my O360 FI, EI RV6A. It is 1214 n.m. straight line, or 1400 s.m., and I typically use 120 gallons round trip. That equates to 23.3 statute miles per gallon (at 185 statute miles per hour). We've driven the route also, and it is 1750 s.m., so comparing apples to apples the RV's mileage would be 29.

The mpg performance numbers for RVs probably varies more than any single other parameter, since the fuel flows vary so widely. For that reason alone, I am very glad I have FI and EI, both of which contribute appreciably.
 
118 HP VS 160 HP

Consider this. Go ahead and put the 160 HP Lyc in and when prudent throttle back to a fuel burn of the 118 HP engine. I realize that would take a lot of self control, but when you really need the power for those high density altitude take-offs you would have it. When you really want to conserve just throttle back. Also, you would get to altitude a lot sooner where you could really save (assuming no winds).

Tom
 
On average, flying distances are about 80% as far as driving distances. So an RV getting 22 MPG (180 mph burning 8 gph, rounding down) would be equivalent to a car getting 27.5 mpg.

The poster listed a 150 HP RV-9, which could burn mogas (I know, we had that discussion a couple days ago), so fuel per gallon need not cost more than gas for a car if he doesn't have to refuel at an airport. If you have to burn avgas, around here it is about 30% more than mogas, so that gives you effectively 19.5 mpg (27.5 x 0.7).

RV is much faster & more fun, but you have to rent/borrow a car when you get there. Cars rarely get delayed for weather. RV's rarely get tied up in traffic.
 
gorbak said:
How does the gph of a 118hp compare to a 160hp lycoming?

Extrapolating Van's numbers for the 118 hp engine (and checking the Lycoming Engine Manual) we get an estimation that follows:

Full power 173 mph 4.53 flight hrs 7.5 gal/hr
(assuming 34 gal. usable..start/taxi/takeoff...)
75% power 166 mph 5.27 flight hrs 6.45 gal/hr
55% power 150 mph 6.90 flight hrs 4.92 gal/hr
Click to expand...
Van's RV-9A, N129RV, burned 6.1gph at 179.6mph (29.4mpg) when tested by the Cafe Foundation. Power was provided by a 160 horse O-320. That engine can be operated on premium automotive gasoline, too.
 
>> That engine can be operated on premium automotive gasoline, too.

>> The poster listed a 150 HP RV-9, which could burn mogas

Curious, where does this information come from? From what I've seen on Lycoming's website, they say nothing but AVGAS for all their engines. How does one know whether you can really safely run MOGAS in these engines?

>> Consider this. Go ahead and put the 160 HP Lyc in and when prudent throttle back to a fuel burn of the 118 HP engine

Be interesting to see how the consumption rates compare for the two engines running at the same speed, say 150mph. The 160HP would be going that speed at a lower power setting, but it's a bigger engine overall. I wonder how close the GPH would be between the two engines running at the same speed (150MPH).
 
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Weather factor

I have had to park my plane (twice ) in bad weather and take the Greyhound home. No fun at all. Then I had to arrange to get back and retreive the plane. The saying goes, "When you have time to spare, go by air". I never leave home without bus fare. Having said that, I have made seven trips from Salem Oregon to Southern California in my RV and it's far better to fly than drive.
 
prkaye said:
>> That engine can be operated on premium automotive gasoline, too.

>> The poster listed a 150 HP RV-9, which could burn mogas

Curious, where does this information come from? From what I've seen on Lycoming's website, they say nothing but AVGAS for all their engines. How does one know whether you can really safely run MOGAS in these engines?
Click to expand...
Peterson Aviation has done extensive testing on auto fuel use in aircraft engines. They sell auto fuel STCs. You can see a list of engines on their website, www.autofuelstc.com
>> Consider this. Go ahead and put the 160 HP Lyc in and when prudent throttle back to a fuel burn of the 118 HP engine

Be interesting to see how the consumption rates compare for the two engines running at the same speed, say 150mph. The 160HP would be going that speed at a lower power setting, but it's a bigger engine overall. I wonder how close the GPH would be between the two engines running at the same speed (150MPH).
Click to expand...
So close as to be negligible. Regardless of the engine, an aircraft takes X amount of power to go Y speed. Assuming engines of similar efficiency (and most typical aircraft engines are) the fuel burn will be very close to the same.

If you come across some reliable performance numbers for an O-235 equipped RV-9, compare them to the Cafe Foundation report on the O-320 powered N129RV. The O-320 -9 will at least match the O-235 for efficiency in most situations.
 
prkaye said:
Be interesting to see how the consumption rates compare for the two engines running at the same speed, say 150mph. The 160HP would be going that speed at a lower power setting, but it's a bigger engine overall. I wonder how close the GPH would be between the two engines running at the same speed (150MPH).
Click to expand...
The smaller engine will probably have a very slightly lower fuel burn, but the difference might be too small to measure. The small engine has three things going for it in this scenario:

1. smaller displacement means less frictional losses to turn it at a given rpm,

2. the throttle will be further open than the one on the larger engine, leading to lower pumping losses, and

3. the aircraft with the smaller engine should be a bit lighter than the one with the larger engine. The lighter weight should mean a bit less induced drag.
 
(disclaimer) I'm only repeating what I have heard about the 118 hp gph.

I have been told that the 118 hp engine uses about 5 - 6 gph in econ. cruise.

According to Van's (and I think their numbers are pretty accurate) that would have you zooming along at 150 mph.

The biggest draw back for flying to visit relatives and such is ground transportation. Yeah, they can pick you up and drop you off but I would rather rent a car. Of course the "Wanna fly in my plane?" usually gets instant cooperation from anyone.

If your trying to save money by flying instead of driving - you might actually come out better going commercial.

HOWEVER! Getting in YOUR plane and flying yourself to whatever destination you desire brings into light the COOL factor. The COOL factor outweighs any and all cost or time considerations.
 
Robert M said:
HOWEVER! Getting in YOUR plane and flying yourself to whatever destination you desire brings into light the COOL factor. The COOL factor outweighs any and all cost or time considerations.
Click to expand...

That pretty much says it all.
 
Robert M said:
HOWEVER! Getting in YOUR plane and flying yourself to whatever destination you desire brings into light the COOL factor. The COOL factor outweighs any and all cost or time considerations.
Click to expand...
Flying in the big birds is like taking a Greyhound buss After 9/11 and all the so called security measures, I now avoid flying commercial every chance I get. I can't wait until my -9 is finished!

Robert, where in SC are you located?
 
That definitely says it all

And:

jsherblon said:
I've never lost my luggage when I'm the pilot.
Click to expand...

And was it Doug or Rosie that said that he could take his handgun and nail clippers too? Plus the plane leaves when and where you usually want it to.

Back to the small engine debate:

Wouldn't an RV-9 with an O-235 at 118 HP still use close to the same amount of gas as a 110 HP Cessna 152 at any given RPM?
 
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