Fuel efficiency...what MPG do you get? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Rooster's82 · 03-25-2008, 05:06 PM

So, a few questions about fuel economy and the 73-87 chevy pickup.

What are you running (engine, tranny, gears, mods) and what are you getting for MPG?

How do you squeeze every last mile out of a tank?

If you could build a truck from the ground up what do you think would be the most fuel efficient setup?

(i have no clue what my MPG is at the moment, my speedo doesn't work right now...but it doesn't seem to be as bad as i thought it would be)

swb85 · 03-25-2008, 05:35 PM

-383ci stroker (~450hp/475ft lbs)
-M21 4 speed
-3.42 gears, 28" tires

14-15 MPG (50/50 city/highway)

If I were building a truck from the ground up and wanted max fuel efficiency, I'd do a LS1/T56 swap.

piecesparts · 01-15-2015, 02:22 PM

Quote:

Originally Posted by swb85

-383ci stroker (~450hp/475ft lbs)
-M21 4 speed
-3.42 gears, 28" tires

14-15 MPG (50/50 city/highway)

If I were building a truck from the ground up and wanted max fuel efficiency, I'd do a LS1/T56 swap.

I have almost the same setup. 383 stroker, 3.73 gears 700R4 tranny (we just put in the lock up converter, it was without the lock up feature until now), 28" tires, dual exhaust, 650 CFM carb. Prior to adding the Lock up converter, I averaged 15 MPG on long trips.

I agree, with the idea of a LS series engine and a T56 tranny. Good horsepower and a lot of room to adjust.

**MikeB** · 01-16-2015, 02:12 PM

Quote:

Originally Posted by swb85

-383ci stroker (~450hp/475ft lbs)
-M21 4 speed
-3.42 gears, 28" tires

14-15 MPG (50/50 city/highway)

Wow, that's great! My 69 C10 had a fairly mild 383 (maybe 350 hp) with a 600 CFM carb, 3.08 axle, and 29" tires. Best it ever got on the highway was 12-13 mpg. Probably got more like 10 around town. Even with a very mild 350 and a Holley Economaster 450 carb, the truck got 14-15 hwy. Both engines had 2-1/4" dual exhausts and were in excellent tune.

No numbers on my 82 C10 with 250 six, but will post some when I get the 355 installed. Should be pretty good with a mild GM roller cam, Vortec heads, and a 2.73 axle. Maybe 16-17 highway?

I think the biggest problems with these trucks is wind resistance. And you can't tune that out or make up for it with taller gearing.

**old Rusty C10** · 03-25-2008, 06:02 PM

well i have a 305 with a th350 recently rebuilt unknown gears and my truck gets about 5-7 mph in NYC the carb seems to be off so im going to go back to a non edelbrock carb

SBTork · 03-25-2008, 06:19 PM

the rig- 86 C-10
350 V8, TH350 transmission, an old tired rochester carb
I drive about 80% city and 20% highway, when I do drive it
It has stock 3:08 rear gears, and for some reason it has 31x10.5x15 tires on a 2wd
The only mods I have are royal purple engine oil, no cat converter, flowmaster muffler, and a K&N air filter.
Last time I checked, I got 10mpg. I think it's due to the ineffiency of the carb, and the way I drive it.

nico · 03-25-2008, 06:26 PM

1984 SWB
383 - around 400hp
Manual Valvebody TH400
2900 stall converter
3.73 gearsl/Detroit Locker
275-60-15's

8-10 mpg.

If all I wanted was fuel economy, I would do a 283 or 302 with a two-barrel Holley, 200R4, 3.08's, should be good for over 20 mpg on the highway...

flamingbig10 · 03-25-2008, 07:05 PM

350 300hp edlebroc 650
th350
373 gears

275/60-15 tire

6 to 7 mpg I would get about 12 if I keep my foot out of it

LOHRTBT · 03-25-2008, 07:14 PM

I averaged 15mpg on my last tank.
92 carbd 350 with a th350 and 3:08 rear. I drive it like an old man lol

knightlife · 03-25-2008, 07:16 PM

8 if Im lucky, on a downhill slope, and the wind is on my tail end...

I pass everything BUT a gas station...

**Gregski** · 01-25-2015, 12:51 AM

Quote:

Originally Posted by knightlife

8 if Im lucky, on a downhill slope, and the wind is on my tail end...

I pass everything BUT a gas station...

LOVE IT, sounds about right !!!

Mickey_D · 03-25-2008, 07:29 PM

1981 K10 305/350 all stock. No muffler, VERY low gears (5.56 or lower), 235/75R15's.

It's about 400-500 pounds lighter than stock due to the rust.

I get between 6-10mpg on it depending on weather. I live out on the prairie so I get the full brunt of ANY wind flat in my face. Generally when I'm late getting to work so I've got my foot in it.

BTW, a block from my house I'm doing 65mph for the 10 miles to work, so pretty much all my driving is highway.

streetstar · 03-25-2008, 08:27 PM

88 K5 blazer, stock 350 tbi, 700r4 tranny, unknown rear gears.
14 mpg hwy, 10 or 11 in town

75 C-10. 454, th350 - also unknown rear gears -- might get 9 or 10 at best

(i dont drive 'em much anymore, but the 14 hwy my k5 gets is not much worse than my new 5.4l F150)

ctouchet · 03-25-2008, 11:01 PM

11 MPG but i need some work on the carb.

69BBsuburban · 03-26-2008, 02:30 AM

I'd be lucky if I get near 12mpg.....but that's not the point of my truck. If I was worried about MPG, I'd be driving a 'Yota.....

I guess you could try to build a '73-up truck to get OK MPG, FI smallblock, tall gears, OD, etc....but the truck is still a BRICK......

zombiescustoms · 03-26-2008, 04:04 AM

89 454 TBI Burban, just did a 300 mile trip and got a solid 10 MPG thinking of putting a TB spacer, injector spacer and an adjustable fuel pressure reg on , supposed to help mileage.

chevymotocross · 03-26-2008, 04:24 AM

87 Silverado swb 2wd
engine: high mileage 305 TBI
transmission: 700r4
tires: 265/75/15
gear ratio: not sure, but probably pretty high highway gears

I'm only getting about 12 mpg driving pretty easily. I'm a bit dissapointed since I thought the tbi would get a bit better mileage but it does have some pretty big tires, which I plan on dropping to a 255/70/15, and the motor is a bit tired.

gchemist · 03-26-2008, 04:35 AM

Last time I posted BS started walking because some people don't think it's possible.

old stock 305 - 18 MPG at 70 MPG. Drove straight though the tanks too. Long 1000 mile trips.
305 - 13 MPG in the city. Lots of work on engine and truck.

ZZ4 - 13 MPG in the city so far. I can't seem to keep my foot out of it. 2500 stall and higher than normal shift points until the tranny is well broken in. I can't wait for a long trip out of town. I'm really curious on what it can pull off. Planning a trip in May. I'll drive through full tanks and calculate.

84 400 · 03-26-2008, 08:30 AM

400- preformer II intake, 650 thunder carb, mild ( i mean mild RV cam crane i think), HEI, serp belt, hooker long tubes, flowmaster 50's with stock Y pipe and cat.
TH350C with Hurst shift kit. TQ is unknown stall
Stock open 10 bolt rear with the shatty 273's

On the high way i get about 12-15 MPG

James McClure · 03-26-2008, 12:22 PM

After seeing and reading what I see here I guess I'm pretty lucky. I can understand Bob (Rusty) only getting 5 to 7 MPG in NYC on account it takes 3 days to cover that much ground, but the rest of you guys at 10 to 12?? Mine is an 84 K20 all stock. The engine has 465,000 miles on it and all I have ever done to it is rebuild the Q jet 4 times and do a valve job at 250,000. I did swap out the oil pan for a 5 qt and use the tall GM oil filters and really good oil (Mobile 1) Truck does ALL highway miles. Specs are 350 cid "M" eng 285 HP, Q jet carb, HD4 speed manual, 3:73 gears and tires are 235-85-R16 and a real light right foot. 15 to 17 MPG loaded or empty. jim 33 year GM mechanic

bb1979 · 03-26-2008, 02:19 PM

Bout 12 with a 454, t400 combo 4.56 gears and 33 x 12.5 tyres running straight propane, average driving conditions, hope to improve that with the addition of the gear vendors I have

Rooster's82 · 03-26-2008, 07:29 PM

I really need to get my speedo working. I feel like im getting over 12 but have no clue. i drive 12 miles to work each way, and i have made the trip 3 times plus errons and stuff over the weekend and im still on tank one with 1/4 left. So....about 100 miles on 12 gallons (16 gallons/.75)...12mpg?

PS. I cruz, no lead foot here, and the drive is on US 19 so the average speed is 45-60mph.

TexasJeff · 03-26-2008, 08:54 PM

1980 3/4 ton, stock carbed 350 bored .030 over, turbo 350, 3.73 gear, I average 11 mpg no matter city or hwy, how fast or if I am pulling my camper I can always count on right around 11.

rfmaster · 03-27-2008, 01:41 AM

1975 C20 long bed with clamp shelf.
Engine 350 with a mild RV cam, TBI and custom real time tuning (highway lean cruise not enabled, yet)
Transmission 700R4 with stock converter (about 1400 RPM)
Rear end 4:10 with 33 inch tires

Highway about 17 mpg, city 13 mpg. Previously, before converting to EFI with Q-Jet i was getting 12 mpg on highway and 9 in city.

//RF

killthewabbit · 03-27-2008, 07:08 AM

engine: reman 350 vortec w/headers, performer 600 cfm
tranny: reman TH350
rear: no idea
tires: 255/70-15

I get 15 with a pretty long freeway drive to work.

03-25-2008, 05:06 PM	#1
Rooster's82 Registered User Join Date: Mar 2008 Location: Clearwater FL Posts: 271	Fuel efficiency...what MPG do you get? So, a few questions about fuel economy and the 73-87 chevy pickup. What are you running (engine, tranny, gears, mods) and what are you getting for MPG? How do you squeeze every last mile out of a tank? If you could build a truck from the ground up what do you think would be the most fuel efficient setup? (i have no clue what my MPG is at the moment, my speedo doesn't work right now...but it doesn't seem to be as bad as i thought it would be) __________________ JG If you can't find it at the junk yard you don't need it.

03-25-2008, 05:35 PM	#2
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Re: Fuel efficiency...what MPG do you get? -383ci stroker (~450hp/475ft lbs) -M21 4 speed -3.42 gears, 28" tires 14-15 MPG (50/50 city/highway) If I were building a truck from the ground up and wanted max fuel efficiency, I'd do a LS1/T56 swap. __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD

03-25-2008, 06:02 PM	#5
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,259	Re: Fuel efficiency...what MPG do you get? well i have a 305 with a th350 recently rebuilt unknown gears and my truck gets about 5-7 mph in NYC the carb seems to be off so im going to go back to a non edelbrock carb __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

03-25-2008, 06:19 PM	#6
SBTork Garage wrench Join Date: Feb 2008 Location: LaCrosse, WI Posts: 1,856	Re: Fuel efficiency...what MPG do you get? the rig- 86 C-10 350 V8, TH350 transmission, an old tired rochester carb I drive about 80% city and 20% highway, when I do drive it It has stock 3:08 rear gears, and for some reason it has 31x10.5x15 tires on a 2wd The only mods I have are royal purple engine oil, no cat converter, flowmaster muffler, and a K&N air filter. Last time I checked, I got 10mpg. I think it's due to the ineffiency of the carb, and the way I drive it. __________________ -Adam 90 V1500 GMC Suburban 350/700R4/NP241..... 01 Saturn SL1 stock DD.....

03-25-2008, 06:26 PM	#7
nico Registered User Join Date: Nov 2006 Location: Marietta, OK Posts: 153	Re: Fuel efficiency...what MPG do you get? 1984 SWB 383 - around 400hp Manual Valvebody TH400 2900 stall converter 3.73 gearsl/Detroit Locker 275-60-15's 8-10 mpg. If all I wanted was fuel economy, I would do a 283 or 302 with a two-barrel Holley, 200R4, 3.08's, should be good for over 20 mpg on the highway...

03-25-2008, 07:05 PM	#8
flamingbig10 6.0 powered square Join Date: Feb 2008 Location: Mesquite texas Posts: 3,459	Re: Fuel efficiency...what MPG do you get? 350 300hp edlebroc 650 th350 373 gears 275/60-15 tire 6 to 7 mpg I would get about 12 if I keep my foot out of it __________________ Aaron 1980 c-10 short bed lowered, cammed 6.0, 4l80e 3600 stall, smp tune, wilwoods, and flames best time so far best et 7.86 @87 on motor 7.57 90 on a 75 shot Build http://67-72chevytrucks.com/vboard/s...d.php?t=283326

03-25-2008, 07:14 PM	#9
LOHRTBT BeWarE tHe eViL CrAnkTOe! Join Date: Oct 2002 Location: Yukon, OK Posts: 3,605	Re: Fuel efficiency...what MPG do you get? I averaged 15mpg on my last tank. 92 carbd 350 with a th350 and 3:08 rear. I drive it like an old man lol __________________ ~Dave~ You can call me Mike, Mike Oxlong - 1986 Chevy SWB - Stock for now - *1986 Chevy Custom SWB* *Stolen 6/26/05* - 1985 Chevy SWB SOLD - 1999 T/A Some mods www.cardomain.com/id/ramairdave AIM Screenname - Jester84

03-25-2008, 07:16 PM	#10
knightlife Dark Heart Motorsports Join Date: Apr 2007 Location: 29404 DKFX Posts: 683	Re: Fuel efficiency...what MPG do you get? 8 if Im lucky, on a downhill slope, and the wind is on my tail end... I pass everything BUT a gas station... __________________ How Deep Can YOU Bleed..? 1985 Chevy Blazer K5- 6.2 N/A, 400 turbo trans CUCV, 12v converted... a new chapter 2005 GMC Sierra Crew Cab 6.0 powwwaa!!! custom jumpseat install w/ captain seats, Hypertech tuner, MSD Blaster Coils, CB and twin antenna's, all electric interior, touch screen in dash. custom center console, with jump seat replacing original console. 1500 HD!

03-25-2008, 07:29 PM	#12
Mickey_D Dirteh Kitteh Join Date: Nov 2006 Location: Mormon country Posts: 2,484	Re: Fuel efficiency...what MPG do you get? 1981 K10 305/350 all stock. No muffler, VERY low gears (5.56 or lower), 235/75R15's. It's about 400-500 pounds lighter than stock due to the rust. I get between 6-10mpg on it depending on weather. I live out on the prairie so I get the full brunt of ANY wind flat in my face. Generally when I'm late getting to work so I've got my foot in it. BTW, a block from my house I'm doing 65mph for the 10 miles to work, so pretty much all my driving is highway. __________________ Darrin 1955 Willys CJ-5 all original and the oldest CJ-5 on the road. 2001 Dodge Neon (wife's car) 1995 Jeep Grand Cherokee Limited Edition SOLD 1981 K15 Custom Deluxe 4X4, rusty but trusty wood hauler. SOLD 1993 S-10 4X4 Tahoe SOLD Sign up with the Contact List RIP ESLL

03-25-2008, 08:27 PM	#13
streetstar Registered User Join Date: May 2007 Location: Moore, Oklahoma Posts: 2,396	Re: Fuel efficiency...what MPG do you get? 88 K5 blazer, stock 350 tbi, 700r4 tranny, unknown rear gears. 14 mpg hwy, 10 or 11 in town 75 C-10. 454, th350 - also unknown rear gears -- might get 9 or 10 at best (i dont drive 'em much anymore, but the 14 hwy my k5 gets is not much worse than my new 5.4l F150) __________________ Are you retired too? Nonsense! I'm in my prime

03-25-2008, 11:01 PM	#14
ctouchet Registered User Join Date: Nov 2005 Location: Maurice,Louisiana Posts: 169	Re: Fuel efficiency...what MPG do you get? 11 MPG but i need some work on the carb. __________________ 2012 F150 SuperCrew 2011 GMC 1500 (COMPANY TRUCK) 1982 Chevy Blazer 2WD (Work in Progress)

03-26-2008, 02:30 AM	#15
69BBsuburban Right in front of you. Join Date: Jan 2006 Location: Roy, Wa Posts: 584	Re: Fuel efficiency...what MPG do you get? I'd be lucky if I get near 12mpg.....but that's not the point of my truck. If I was worried about MPG, I'd be driving a 'Yota..... I guess you could try to build a '73-up truck to get OK MPG, FI smallblock, tall gears, OD, etc....but the truck is still a BRICK...... __________________ Pinstriping by Josh '78 Chevy Silverado SWB (lowered, 454) '90 Chevy Sport Truck '68 Dodge Charger R/T 1930 Ford Model A

03-26-2008, 04:04 AM	#16
zombiescustoms Registered User Join Date: Mar 2008 Location: Abingdon, MD Posts: 74	Re: Fuel efficiency...what MPG do you get? 89 454 TBI Burban, just did a 300 mile trip and got a solid 10 MPG thinking of putting a TB spacer, injector spacer and an adjustable fuel pressure reg on , supposed to help mileage.

03-26-2008, 04:24 AM	#17
chevymotocross Registered User Join Date: May 2007 Location: East Haven, CT Posts: 882	Re: Fuel efficiency...what MPG do you get? 87 Silverado swb 2wd engine: high mileage 305 TBI transmission: 700r4 tires: 265/75/15 gear ratio: not sure, but probably pretty high highway gears I'm only getting about 12 mpg driving pretty easily. I'm a bit dissapointed since I thought the tbi would get a bit better mileage but it does have some pretty big tires, which I plan on dropping to a 255/70/15, and the motor is a bit tired.

03-26-2008, 04:35 AM	#18
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: Fuel efficiency...what MPG do you get? Last time I posted BS started walking because some people don't think it's possible. old stock 305 - 18 MPG at 70 MPG. Drove straight though the tanks too. Long 1000 mile trips. 305 - 13 MPG in the city. Lots of work on engine and truck. ZZ4 - 13 MPG in the city so far. I can't seem to keep my foot out of it. 2500 stall and higher than normal shift points until the tranny is well broken in. I can't wait for a long trip out of town. I'm really curious on what it can pull off. Planning a trip in May. I'll drive through full tanks and calculate. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos



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03-26-2008, 08:30 AM	#19
84 400 Sb 400 club Join Date: Nov 2005 Location: NH / MA Posts: 2,741	Re: Fuel efficiency...what MPG do you get? 400- preformer II intake, 650 thunder carb, mild ( i mean mild RV cam crane i think), HEI, serp belt, hooker long tubes, flowmaster 50's with stock Y pipe and cat. TH350C with Hurst shift kit. TQ is unknown stall Stock open 10 bolt rear with the shatty 273's On the high way i get about 12-15 MPG __________________ 1984 chevy c10, built 400sb,.(SOLD) 77 K10 Project / daily driver "The Grinch" http://67-72chevytrucks.com/vboard/s...d.php?t=318363 1956 Willys Wagon (327 chevy) Project (Now Buick 225) 1980 Corvette L-48 4 speed 1992 Mustang GT built 5.0 5 speed 1985 C10 LWB Sold 1982 K10 SWB plow truck Parted out 1986 D30 M1028 fire brush truck Parted out

03-26-2008, 12:22 PM	#20
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Fuel efficiency...what MPG do you get? After seeing and reading what I see here I guess I'm pretty lucky. I can understand Bob (Rusty) only getting 5 to 7 MPG in NYC on account it takes 3 days to cover that much ground, but the rest of you guys at 10 to 12?? Mine is an 84 K20 all stock. The engine has 465,000 miles on it and all I have ever done to it is rebuild the Q jet 4 times and do a valve job at 250,000. I did swap out the oil pan for a 5 qt and use the tall GM oil filters and really good oil (Mobile 1) Truck does ALL highway miles. Specs are 350 cid "M" eng 285 HP, Q jet carb, HD4 speed manual, 3:73 gears and tires are 235-85-R16 and a real light right foot. 15 to 17 MPG loaded or empty. jim 33 year GM mechanic __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

03-26-2008, 02:19 PM	#21
bb1979 Registered User Join Date: Apr 2007 Location: NSW, Australia Posts: 205	Re: Fuel efficiency...what MPG do you get? Bout 12 with a 454, t400 combo 4.56 gears and 33 x 12.5 tyres running straight propane, average driving conditions, hope to improve that with the addition of the gear vendors I have __________________ 1979 C20 pickup 454 big block turbo 400, 4.56 gears

03-26-2008, 07:29 PM	#22
Rooster's82 Registered User Join Date: Mar 2008 Location: Clearwater FL Posts: 271	Re: Fuel efficiency...what MPG do you get? I really need to get my speedo working. I feel like im getting over 12 but have no clue. i drive 12 miles to work each way, and i have made the trip 3 times plus errons and stuff over the weekend and im still on tank one with 1/4 left. So....about 100 miles on 12 gallons (16 gallons/.75)...12mpg? PS. I cruz, no lead foot here, and the drive is on US 19 so the average speed is 45-60mph. __________________ JG If you can't find it at the junk yard you don't need it. Last edited by Rooster's82; 03-26-2008 at 07:32 PM.

03-26-2008, 08:54 PM	#23
TexasJeff Don't Crush em Restore em Join Date: Aug 2004 Location: Pinehurst, Texas Posts: 764	Re: Fuel efficiency...what MPG do you get? 1980 3/4 ton, stock carbed 350 bored .030 over, turbo 350, 3.73 gear, I average 11 mpg no matter city or hwy, how fast or if I am pulling my camper I can always count on right around 11. __________________ TexasJeff 2009 Silver with Linen Interior Cadillac DTS 1990 Red with White Top and Interior Ford Mustang GT convertible 1998 Red with Gray Interior, C3500 Chevy Crew Cab Dually

03-27-2008, 01:41 AM	#24
rfmaster Registered User Join Date: Oct 2003 Location: OC CA Posts: 1,374	Re: Fuel efficiency...what MPG do you get? 1975 C20 long bed with clamp shelf. Engine 350 with a mild RV cam, TBI and custom real time tuning (highway lean cruise not enabled, yet) Transmission 700R4 with stock converter (about 1400 RPM) Rear end 4:10 with 33 inch tires Highway about 17 mpg, city 13 mpg. Previously, before converting to EFI with Q-Jet i was getting 12 mpg on highway and 9 in city. //RF __________________ "The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17)

03-27-2008, 07:08 AM	#25
killthewabbit Spear and magic helmet! Join Date: Oct 2006 Location: Nashville, TN Posts: 1,226	Re: Fuel efficiency...what MPG do you get? engine: reman 350 vortec w/headers, performer 600 cfm tranny: reman TH350 rear: no idea tires: 255/70-15 I get 15 with a pretty long freeway drive to work.

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