The (Don't Yawn!) Fuel Economy thread!

[IJ Reilly]

I am ridiculously jealous. I'd love to go out and really fly again.

I've been unable to fly for quite a while, since I let my medical expire due to health issues. I'm finally ready to duke it out with the FAA, and hope to start up again this summer. Of course now avgas is over $5.00/gallon, which will take some of the joy out of it.

 

[dmr727]

I've been unable to fly for quite a while, since I let my medical expire due to health issues. I'm finally ready to duke it out with the FAA, and hope to start up again this summer. Of course now avgas is over $5.00/gallon, which will take some of the joy out of it.

Good luck with the FAA! And hey, at least you own a 172. I'd hate to have to feed a 520 or 540 these days - or even worse, a pair of them.

 

[LeeTom]

i get 29mpg. my vehicle? a 1971 vw bus.

 

[Berlepsch]

i do know that. but when it is fully engaged, it is the same as you being in neutral

This is only true as far as the clutch disks are considered. When you engage the clutch, you will put axial stress on some roller bearings that are needed to seperate the clutch. And replacing these bearings when they are worn is usually about as expensive as replacing the clutch disks. To maximize the life of your clutch mechanism, avoid slipping and extended engagement of the clutch.

 

[dmr727]

i get 29mpg. my vehicle? a 1971 vw bus.

Hippie!

 

[mark!]

I drive a 1983 BMW 533i, it gets about 17 miles a gallon in the city
I get about 220 MPG a tank. On the highway it gets around 25 MPG.

I typically drive 10 miles a day on weekdays and 100+ on weekends.
I try not to drive much...

 

[IJ Reilly]

Good luck with the FAA! And hey, at least you own a 172. I'd hate to have to feed a 520 or 540 these days - or even worse, a pair of them.

Thanks. I haven't checked recently but I'll bet you could buy a light twin cheap these days!

To the topic, a light single like a Cessna 172 gets about 16 MPG at cruise.

 

[Lord Blackadder]

I drive a 1983 BMW 533i, it gets about 17 miles a gallon in the city
I get about 220 MPG a tank. On the highway it gets around 25 MPG.

You could always swap it out for a 325e or 325es or even a 318 for better fuel economy. But then again, why buy a gasoline engined BMW for fuel economy?...oh wait - you can't get a diesel BMW in the states.

To the topic, a light single like a Cessna 172 gets about 16 MPG at cruise.

That sounds pretty good considering the large displacement of the engine.

 

[dmr727]

That sounds pretty good considering the large displacement of the engine.

Yeah, it certainly does. One of the best planes ever built when you look at efficiency and cost vs. utility.

IJ - does your plane have the 320 or 300 in it? I thought Cessna switched to the O-320 in the late 60's, but can't remember exactly when.

 

[mark!]

You could always swap it out for a 325e or 325es or even a 318 for better fuel economy. But then again, why buy a gasoline engined BMW for fuel economy?...oh wait - you can't get a diesel BMW in the states.

Haha yeah, we had a 528e but it drove me crazy...and I even thought about getting a 524td! That's the last diesel sold in the states that I know of... but I tend to stay away from the 3 series...

 

[IJ Reilly]

Yeah, it certainly does. One of the best planes ever built when you look at efficiency and cost vs. utility.

IJ - does your plane have the 320 or 300 in it? I thought Cessna switched to the O-320 in the late 60's, but can't remember exactly when.

Exactly in 1968. That was the first year they put the Lycoming O-320 into the 172, before that it was the Continental O-300. The efficiency isn't too bad when you consider that it's an adapted tractor engine from the 1950s. Produces a whopping 150 hp at sea level.

The biggest problem with the 172 is that it's slow, slow, slow -- about 103 knots of cruise on a good day at 7.5 GPH. I do lust after one of the newer composite airplanes that will give you 120 knots of cruise at 4.5 GPH. That's about 30 MPG!

There's kind of good story about how the O-320 made it into the 172. In 1968, Cessna planned on replacing the 172 with the far more modern 177 Cardinal. They bought a load of the Lycoming engines for that airplane -- but the 177 was too heavy to perform adequately with 150 hp, and Cessna pilots hated it for other reasons, so they used their stock of Lycoming engines in the 172 instead. They tried for about ten years to perfect the Cardinal, and even built a retract version, but pilots never really accepted the airplane. It was discontinued, but the 172 is still made, I believe 55 years now after it was first introduced, 60 if you include the 170 on which it was based.

 

[twoodcc]

This is only true as far as the clutch disks are considered. When you engage the clutch, you will put axial stress on some roller bearings that are needed to seperate the clutch. And replacing these bearings when they are worn is usually about as expensive as replacing the clutch disks. To maximize the life of your clutch mechanism, avoid slipping and extended engagement of the clutch.

i totally agree. that's why i coast in neutral, instead of sitting there with my foot on the clutch

 

[Lord Blackadder]

Haha yeah, we had a 528e but it drove me crazy...and I even thought about getting a 524td! That's the last diesel sold in the states that I know of... but I tend to stay away from the 3 series...

What's wrong with the 3 series? Personally I think that the best sedan BMW makes is the 540i, especially the E39 version. The newer ones don't look as good. But the 5-series is a pretty big car, and I'm into smaller cars these days.

Favorite BMWs : 2002, E30 M3, E24 635CSi/M6, E39 540i/M5