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Purple Frog (Forum Supporter)
Purple Frog (Forum Supporter) HalfDork
7/20/21 9:14 a.m.

Currently in the fleet: a 39' motorhome with GM 8.1 liter gas engine.

6.5 mpg.  Doesn't matter if its going uphill, downhill with a tailwind, pulling the toad, pulling the race trailer, not pulling anything.  6.5 mpg.

GIRTHQUAKE
GIRTHQUAKE Dork
7/20/21 10:14 a.m.

I'mma cheat a little bit.

My only amublance in a small town of BFE Midwest was based on I think a F-550 chassis; it was one of the biggest vheicles I'd ever seen, so huge it couldn't fit into the standard Ambulance parking spaces at the ER. berkeley, it barely could fit in a lane. It was a Canadian built "Winter Package" vehicle meant to carry flight teams and even up to surgical teams, so this monster had at least another foot added onto it's length. Looking back I probably should have had a CDL to drive it, but the Private EMS industry is seemingly shady by design.

It's over 330,000 miles on a first gen 7.3. Even as a turbodiesel, I think it might have gotten 3-5MPG city, possibly as high as 6 on highway. It had a 50-60 gallon fuel tank (!) so it was hard to gauge its mileage.

oldrotarydriver
oldrotarydriver Reader
7/20/21 3:35 p.m.

Easily the '96 Jayco motorhome, blocking sunlight and digging divots in my wallet. SO bought it significantly used, and it's been dining on loose change ever since.

Rough calculations have given back single-digit answers for every trip that involved a hill, dale, dell, headwind or significant curves.  Ford 7.something gas engine.

It spent the last 14 months as my sister's COVID fallout shelter, perched next to my parents' place, so she (hospital IT staffer) wouldn't expose my elderly mother to anything.  So, I owe it at least grudging respect for awhile.

 

barefootskater (Shaun)
barefootskater (Shaun) PowerDork
7/20/21 4:06 p.m.

My very first vehicle, a $500 1977 K10, with the dual cherry bombs and an aftermarket sun roof.  7mpgs unless I opened up the qjet. Gas was $1.79 and it was killing me at 17. 

Tony Sestito
Tony Sestito PowerDork
7/20/21 7:15 p.m.

My '79 Power Wagon by far gets the worst MPG out of anything I've ever owned. With the stock 145hp 318 2bbl, TorqueFlite 727, NP203 full time all-the-time 4WD, and 4:10 gears, the best I've gotten is 9, with the worst being 5. The definition of a pig. 

New York Nick
New York Nick Reader
7/20/21 7:27 p.m.

I have been fairly impressed with my 1995 Suburban's fuel economy. It has the TBI 350 with a 4l60. In 2019 I took it from NY to NC and back and got 16.2 on the trip. Well I just took it from NY to NC (with some side trips) pulling my camper and it averaged 7.43 over 1875 miles. Truck scaled at 5450 lbs and the trailer at 4700 lbs. I guess it makes sense that twice the rolling resistance, twice the frontal area and twice the weight would cut the fuel economy in half but darn 7.43 mpg is tough.

Mr. Lee
Mr. Lee PowerDork
7/21/21 2:04 p.m.

2000 Silverado 2500 4x4 6.0 stock 4L80 and gears with 35" tires. 8-9mpg normal driving. City, highway, mixed, doesn't matter. Hyper mile it, and it would get 11. Maybe.

irish44j (Forum Supporter)
irish44j (Forum Supporter) MegaDork
7/21/21 3:10 p.m.

My 05 Sequoia got 9.5 towing to Ohio Forest Rally. Don't think I've seen lower than that for any vehicles I have. My '10 Sequoia has only been as low as 11.5 towing with +1 size load range E tires. When I bought it I managed 18mpg on full highway haul at 65mph on P-rated tires.  Doubt I'll see that again. 

Claff
Claff Reader
7/21/21 10:14 p.m.

When I graduated high school (1985), my dad had three Corvettes: a '62, a '71 big block coupe, and a '73 convertible. He bought the '73 cheap, fixed what was wrong with it, and it was a decent driver. 350/4-spd, no power steering, no options, screaming yellow. After graduation, he made me an offer I couldn't turn down. If I took the time to make the car show-worthy, I could take it to the local Corvette club car show. I did so, and even won my class. What I shouldn't mention was that classes were broken down way too much, so much so that '73-75 convertibles were their own class, separate from say '68-72 convertibles, and I was the only entrant. But I still have the trophy.

That effort went so well that I was allowed to use the car going forward. I drove it a lot, only on nice days of course. Got pulled over once doing 45 through the sleepy little town of Hinsdale, Mass. but didn't get a ticket. But the cop's wife worked with my mother so that wasn't going to be a secret I could keep. I lost the use of the car for a week, and it would only get worse if that behavior continued (it didn't). I also lost the use of the car for something like a month of primo summer convertible weather when it needed a rear wheel bearing replaced and the shop my dad took it to took forEVER to do the job.

But I digress.

To answer the question, I usually divided out the gas mileage numbers when I filled it up. I still very vividly remember doing the calculation one time and was embarrassed to discover I was getting a whopping 9 MPG.

Surprisingly, I drove that car all the way into October or November. Summer gas was easy to afford as I was working full-time. When I went to college in the fall I cut back to part-time work and suddenly that car was eating up a lot of my income. I finally gave it up after the hardtop went on, and went back to the family driver trainer, dad's '74 El Camino, which probably got 14 MPG so it's not like it made a huge difference. I got my first car in the winter, a '78 Civic, and that got expenentially better mileage.

I have seen worse MPGs than that Corvette, though I don't know if it counts for this thread. We did an all-day test & tune autocross with our recently-acquired 2010 MX-5 back in 2017, and I zeroed the mileage display on the dash before we started making runs. At the end of the day I checked it, and was amused to see we averaged a whopping 5.8 MPG.

P3PPY
P3PPY Dork
7/21/21 10:28 p.m.

Sheesh man, on the track I averaged better than your car! 9.36 mpg. My '89 Olds 3800 getting 11mpg for two tanks tipped me off that the O2 sensor was bad. That was my runner up. 

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) PowerDork
7/22/21 7:27 a.m.

My 04 Ralliart wagon gets a lot worse mileage than you would expect at 21-23. My commute is mostly highway. I have gotten 25 on a highway road trip carrying all four of us and luggage. I rarely drive less than 70, usually closer to 80, so that's a factor. 

DrBoost
DrBoost MegaDork
7/22/21 8:47 a.m.

My 360-powered CJ-7 got about 9, my current 360-powered Grand Cherokee gets 11.

A 401 CJ
A 401 CJ SuperDork
7/22/21 9:43 a.m.
Claff said:

When I graduated high school (1985), my dad had three Corvettes: a '62, a '71 big block coupe, and a '73 convertible. He bought the '73 cheap, fixed what was wrong with it, and it was a decent driver. 350/4-spd, no power steering, no options, screaming yellow. After graduation, he made me an offer I couldn't turn down. If I took the time to make the car show-worthy, I could take it to the local Corvette club car show. I did so, and even won my class. What I shouldn't mention was that classes were broken down way too much, so much so that '73-75 convertibles were their own class, separate from say '68-72 convertibles, and I was the only entrant. But I still have the trophy.

That effort went so well that I was allowed to use the car going forward. I drove it a lot, only on nice days of course. Got pulled over once doing 45 through the sleepy little town of Hinsdale, Mass. but didn't get a ticket. But the cop's wife worked with my mother so that wasn't going to be a secret I could keep. I lost the use of the car for a week, and it would only get worse if that behavior continued (it didn't). I also lost the use of the car for something like a month of primo summer convertible weather when it needed a rear wheel bearing replaced and the shop my dad took it to took forEVER to do the job.

But I digress.

To answer the question, I usually divided out the gas mileage numbers when I filled it up. I still very vividly remember doing the calculation one time and was embarrassed to discover I was getting a whopping 9 MPG.

Surprisingly, I drove that car all the way into October or November. Summer gas was easy to afford as I was working full-time. When I went to college in the fall I cut back to part-time work and suddenly that car was eating up a lot of my income. I finally gave it up after the hardtop went on, and went back to the family driver trainer, dad's '74 El Camino, which probably got 14 MPG so it's not like it made a huge difference. I got my first car in the winter, a '78 Civic, and that got expenentially better mileage.

I have seen worse MPGs than that Corvette, though I don't know if it counts for this thread. We did an all-day test & tune autocross with our recently-acquired 2010 MX-5 back in 2017, and I zeroed the mileage display on the dash before we started making runs. At the end of the day I checked it, and was amused to see we averaged a whopping 5.8 MPG.

9 - 14 is an enormous difference.  Mileage is not naturally intuitive if you don't think about it.  The returns diminish as the mpgs increase.  

It's like the story of the young man and woman both working at the same plant 10 miles from home.  The choice is: him - take the 44" boggers off the dually and go from 5 to 6 or her- tune and hyper-mile the old Rabbit and go from 30 to 50.  Which saves more gas?  It isn't even close.  In fact, even if she could take the Rabbit to 100 mpg, going from 5 to 6 would still be more beneficial.  

edit: i hope i crunched those numbers right.  i only had a pencil

rslifkin
rslifkin UberDork
7/22/21 9:50 a.m.

In reply to A 401 CJ :

Assuming each has 2 weeks vacation per year, that's 250 days x 20 miles round trip, so 5000 miles / year of commuting.  Going from 5 mpg to 6 means the truck goes from 1000 gal / year to 833, or a savings of 166 gallons.  30 mpg to 50 on the Rabbit is 166 gal year vs 100, so only 66 gallons saved.  The truck stands to save as much as the 30 mpg Rabbit burns total.  

buzzboy
buzzboy Dork
7/22/21 12:42 p.m.
A 401 CJ said:

We're on opposite ends of the spectrum.  I'm getting 17 empty with my 7.3 and it's dual rear wheels and 4.10 gears.  Something was wrong if you were getting 8 empty.

And I DD'd an XJ for a dozen years that I bought almost brand new.  It was a stick and had 3.07 gears.  Still struggled to get 15.  

Part of the economy issue was that the 7.3 was in a 22 passenger bus. A loaf of bread weighing 12500lbs. Plus it was geared as a city bus(made towing great).

My XJ is bone stock 96 4.0 5speed with the 3.07s and factory size 29" snow tires. I drive 16 miles each way to work, home at 7000 feet, down to work at 6000 feet. Then every 2 weeks I drive 40 miles and down 2500 feet to buy fuel($1/gal savings and I fill jugs). My worst fillup was during a snow storm week where I only got 19 mpg over 30 gallons.

Barb_Dwyer
Barb_Dwyer New Reader
7/23/21 7:11 a.m.

In reply to A 401 CJ :

While my 2018 Titan fits right in when it's towing, I feel like all these old brass cars will be expected.  When my racecar is in it, the enclosed 24' gets me 7.8 mpg.  Considering that that's an engine from the modern era, it's pretty awful. 

A 401 CJ
A 401 CJ SuperDork
7/23/21 8:56 a.m.

It would be nice if we could find accurate BSFC numbers published for various engines.  

I'm so sick and tired of the only two metrics being peak hp (maybe they publish peak torque maybe not) and mpg according to the EPA driving loop.  

Consumers should demand more.

 

Aaron_King
Aaron_King PowerDork
7/23/21 8:58 a.m.

I was able to get my 99 SAAB 9-3 HOT in the single digits while getting the manual boost controller set up. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/23/21 10:32 a.m.
A 401 CJ said:

It would be nice if we could find accurate BSFC numbers published for various engines.  

I'm so sick and tired of the only two metrics being peak hp (maybe they publish peak torque maybe not) and mpg according to the EPA driving loop.  

Consumers should demand more.

 

The SAE has been cracking down on illegally shared papers, too, so even that avenue is going away.

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