MGB expected MPG? : MGB & GT Forum : MG Experience Forums : The MG Experience

MGB expected MPG? #1
n56545 Rusty Mayes Vacaville, California, USA 1955 MG TF 1500 1967 MG MGB GT	Posted: March 06, 2013 12:58AM Registered: 5 months ago Posts: 88

After owning and driving my 67GT for eight months and some 500 miles, Mostly country road and town in town driving, I am averaging about 15 miles per gallon fuel burn. Is this typical or should I be looking for a carb or ignition problem? I recently found the timing advanced some ten degrees. The engine seems to run fine and have pleny of power. I am planning on an overhaul shortly because of age and low oil pressure. I will do the carbs as well. Just wondering what you guys generally get for mileage.

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Re: MGB expected MPG? #2
applebj8 Jon Appleby Lake Wylie, SC, USA 1971 MG MGB	Posted: March 06, 2013 01:13AM Registered: 7 years ago Posts: 1,302

30+ mpg here - re-manufactured engine, 0.020" over, with twin SU's and overdrive...

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Re: MGB expected MPG? #3
herculesmgb1971 gerard boulanger Hercules, CA, USA 1971 MG MGB MkII	Posted: March 06, 2013 01:31AM Registered: 1 year ago Posts: 700

22-26 MPG with a Weber 32/36 and overdive.

Edited 1 time(s). Last edit at 03/07/2013 07:50PM by herculesmgb1971.

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Re: MGB expected MPG? #4
oily-hands Owen Frankland Stockton on Tees, Cleveland, United Kingdom 1937 MG TA "Numbum" 1971 MG MGB GT "The Bruise" 2002 MG ZR	Posted: March 06, 2013 01:32AM Registered: 3 years ago Posts: 5,152

I'm avaraging about 25mpg (UK gallon) in mixed driving, and I don't drive it gently. On a run using mostly overdrive top I get around 30mpg.

This seems to be the norm from the people I've spoken to about it.

Member of The International Society of Luddites (Unrepentant Chapter).

Take the time to understand what a part does and how it does it, then you'll have a better understanding of how to fix it when it goes wrong. Beats the scattergun approach every time.

Ignition testing made easy.

Making your MGB handbrake work

My You Tube Channel

Life with an MG TA and an MGB GT in the UK.

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Re: MGB expected MPG? #5
the omega man phil wilkins staffordshire, United Kingdom 1973 MG MGB GT	Posted: March 06, 2013 01:51AM Registered: 2 years ago Posts: 1,689

25 to 30 I reckon

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Re: MGB expected MPG? #6
Dell WA Delbert Golightly Spanaway Wash, USA	Posted: March 06, 2013 03:25AM Registered: 1 year ago Posts: 272

dang it Rusty.........DON'T EVER rebuild yer engine 'cuz of low gas mileage until you do the dreaded "compression" test. Yer 1.8L engine should consistently gitt about 25-mpg US. Yer carbs are way outta adjustment. While ignition timing and sparkies will effect yer engine economy, ittza yer carbs. Gitt'em ADJUSTED correctly and then complain about mileage .........Dell, yer self-appointed sparkie-meister

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Re: MGB expected MPG? #7
aarteinen Petri Nieminen Oulu, N/A, Finland	Posted: March 06, 2013 04:21AM Registered: 3 years ago Posts: 10

My '65 Roadster gives me roughly 9 l/100 km or 26 mpg (US) on long haul (when doing more than 300 km w/o breaks) at an average speed of 95 kph (60 mph). 3 synch, non-od, will wear ear protectors ...

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Re: MGB expected MPG? #8
REDWING Steve J SHEFFIELD, United Kingdom	Posted: March 06, 2013 07:13AM Registered: 6 months ago Posts: 5

My '74 BGT with OD gives me 22mpg in town driving and 35mpg on a long run at 50/60mph.
I reckon that equates to around 18mpg and 29 mpg in US gallons.

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Re: MGB expected MPG? #9
tomkatb Larry Baygents Dayton, Ohio, USA 1963 MG MGB	Posted: March 06, 2013 08:29AM Registered: 8 years ago Posts: 3,370

Bone stock 63.

22-28 depending on the operator. No overdrive.

Always step one. Verify 100% the correct operation and model number of the dizzy.

Step two. Retest the dizzy.

Fill in the form, takes 10 minutes.

Initial idle advance___
Advance at 3000rpm___
Advance when applying a vacuum to the advance___
Vacuum advance holds with tongue over the hose, yes/no
Dizzy I'd number___
Is advance steady at idle, yes/no

What carb set up?

If everything is as it should be, the carb may be an issue.

L.W.(Larry)Baygents
63B
77 Spit

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Re: MGB expected MPG? #10
29desoto Wayne Sanders Outside Otis, OR - in the woods!, USA 1965 MG MGB V6 Conversion "Tubby" 1977 MG MGB "Ole Yeller" 1979 MG MGB "Kermit" 1984 Chevrolet Corvette "The Green Weenie" 1994 Chevrolet S10 "Lil Red"	Posted: March 06, 2013 11:02AM Registered: 2 years ago Posts: 6,023

Looking at the OP, I have a couple of questions -

Driven 500 miles in eight months. Sixty miles per month. Unless the car is gassed up at each run, the gas is old.

Low oil pressure. How low?

Was the car previously driven in a similar fashion? Has it been parked more than driven?

I'm thinking a can of Seafoam and a long spirited drive might be the first step, right after going through Larry's check sheet, and checking the valves.

This may be one gummed up car. IMHO.

Wayne Sanders
Rose Lodge, OR

"I don't care to belong to any club that accepts people like me"-joined Willamette Valley Club in 2011

77 MGB - Four tone paint - some kind of electronic ignition - hood props - cheap tires - new springs all around - mixture of poly and rubber bushings - original exhaust - fuzzy seatcovers - stereo out of old F150 pickup - virtually no rust - right front wrecked and semi well repaired - just about right for me!

78 MGB - Done right by a good PO, and I only bought it. Tell Jim how nice it is. But I did put in a Datsun 5 speed.

79/65 MGB - Tubby - Carmine Red - V-6 - T-5
Going to do this one more right, less rat rod!

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Re: MGB expected MPG? #11
Michael74MGB Michael Austin Odessa, TX, USA 1974 MG MGB MkIII "Maggy"	Posted: March 06, 2013 11:09AM Registered: 2 years ago Posts: 932

A while back, someone posted up the EPA estimated mileage from an original window sticker from a 1980 model and it was 16mpg! Mine seems to do around 20 in town, and probably upper 20's on the road - maybe a bit more (been a while since I had it on a long highway drive).

74 MGB: APT VP11 cam, lifters, valve springs; 9:1; ported head; TT exhaust; vernier timing gear; wizard aluminum radiator; dizzy by Jeff S.; stock HIF4's; it goes on and on.....

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Re: MGB expected MPG? #12
n56545 Rusty Mayes Vacaville, California, USA 1955 MG TF 1500 1967 MG MGB GT	Posted: March 06, 2013 11:28AM Registered: 5 months ago Posts: 88

A little back ground on the 500 miles in 8 months. I bought the car last summer and tnen life got in the way of getting it in shape to be a daily driver. It had sat for a while before I bought it. I sent it to the upholstery shop as a back burner project which took three months and then after driving it for a week I got into the front end rebuild which took another month to. Driving in between and since then has been sporatic but "spirited" so I am not surprised that the mileage is a tad low. I will do the analysis and tune the carbs and do some more conservative driving and post any improvement, assuming life stays out of the way!
I really appreciate the response guys. This website really makes playing with the LBC a ton of fun. Funny when I was a kid and the car gave me crap I was annoyed. Now I laugh and have a blast correcting what ever comes up.

Attached is a pic of my shop with the spring's projects.

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Re: MGB expected MPG? #13
oily-hands Owen Frankland Stockton on Tees, Cleveland, United Kingdom 1937 MG TA "Numbum" 1971 MG MGB GT "The Bruise" 2002 MG ZR	Posted: March 06, 2013 11:34AM Registered: 3 years ago Posts: 5,152

I never noticed the 500 miles. That's nowhere near enough miles to calculate mpg.

You need to fill up and drive, note the mileage and fuel used at next fill up, then repeat at least twice more. That should give you a more accurate figure. You might not be doing as badly as you think.

Member of The International Society of Luddites (Unrepentant Chapter).

Take the time to understand what a part does and how it does it, then you'll have a better understanding of how to fix it when it goes wrong. Beats the scattergun approach every time.

Ignition testing made easy.

Making your MGB handbrake work

My You Tube Channel

Life with an MG TA and an MGB GT in the UK.

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Re: MGB expected MPG? #14
stuntflyr Chris McMillin Los Angeles, USA 1965 MG MGB	Posted: March 06, 2013 11:43AM Registered: 1 year ago Posts: 315

In reply to # 2305530 by n56545 After owning and driving my 67GT for eight months and some 500 miles, Mostly country road and town in town driving, I am averaging about 15 miles per gallon fuel burn. Is this typical or should I be looking for a carb or ignition problem? I recently found the timing advanced some ten degrees. The engine seems to run fine and have pleny of power. I am planning on an overhaul shortly because of age and low oil pressure. I will do the carbs as well. Just wondering what you guys generally get for mileage.

I figure 25 MPG.
"Seems to run fine and have plenty of power", means to me; Drive it more, 300 miles out of a tank is normal once one starts driving more than two tanks a year!
Overhaul for low oil pressure? Below 50 at warm cruise? What kind of oil? What weight?
I'd be driving the heck out of it, going on trips to 150-300 mile distant places and record those performance figures before thinking of making any overhaul decisions. Your choke on and idle periods compared to your total gallons burned could throw your mileage comps way out. You aren't driving it enough to be able to tell.
(Go to the airport and buy 5 gallons of 100LL in a can "for your homebuilt airplane's fuel system calibration" and see how it acts after driving that tank through it! Or just add a gallon to each tank, you'll see an improvement. Cali gas alcohol and additives penalties to performance really change when TEL is added to the old GB series engine. Also ask where there are any no alcohol MoGas pumps, airplanes are allowed to use auto gas with no ethanol or additives if they have the approved paperwork and this is good gas for the MGB too. You can lean the SU's out, if you're over say 2500 feet a lot, by a flat and get some better mileage too, but if it "fine" and "powerful" I wouldn't mess with success.)
Chris...

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Re: MGB expected MPG? #15
EmgesMG Robert Emge Red Bluff Ca., USA 1965 MG MGB MkI 1971 MG MGB GT	Posted: March 06, 2013 11:49AM Registered: 2 years ago Posts: 85

My '71 GT gets about 26mpg on regular(87 octane), and about 28mpg on "premium"(92 octane) goes over 30mpg on Nevada premium, if I keep it around 70mph cruising. Stock motor with 90K with OD.

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Re: MGB expected MPG? #16
29desoto Wayne Sanders Outside Otis, OR - in the woods!, USA 1965 MG MGB V6 Conversion "Tubby" 1977 MG MGB "Ole Yeller" 1979 MG MGB "Kermit" 1984 Chevrolet Corvette "The Green Weenie" 1994 Chevrolet S10 "Lil Red"	Posted: March 06, 2013 11:52AM Registered: 2 years ago Posts: 6,023

Looking at your shop, I wonder that you need to ask us questions! Looks to me like you are well into the hobby/addiction!

I was thinking that you might be a young guy expecting these LBC's to put out the mileage of a Honda Civic or something.

Someone at a gas station recently asked me if I got 45 MPG out of my 77 "B". I assured them that I did not.

Wayne Sanders
Rose Lodge, OR

"I don't care to belong to any club that accepts people like me"-joined Willamette Valley Club in 2011

77 MGB - Four tone paint - some kind of electronic ignition - hood props - cheap tires - new springs all around - mixture of poly and rubber bushings - original exhaust - fuzzy seatcovers - stereo out of old F150 pickup - virtually no rust - right front wrecked and semi well repaired - just about right for me!

78 MGB - Done right by a good PO, and I only bought it. Tell Jim how nice it is. But I did put in a Datsun 5 speed.

79/65 MGB - Tubby - Carmine Red - V-6 - T-5
Going to do this one more right, less rat rod!

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Re: MGB expected MPG? #17
OldBloke Jim Legg Napa, California, USA 1971 MG MGB GT 1972 MG MGB V6 Conversion	Posted: March 06, 2013 12:08PM Registered: 5 years ago Posts: 8,229

My '71 never saw more than 16-18 around town, but hwy driving with O/D saw consistent 26-30 MPG. (Always premium gas)

"Not all who wander are lost." -J.R.R. Tolkien

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Re: MGB expected MPG? #18
bobmunch Bob Muenchausen PC, Oregon, USA 1968 MG MGB GT "Traveler"	Posted: March 06, 2013 12:10PM Registered: 13 years ago Posts: 11,524

Just statistics to corroborate what may have already become the consensus:

Stock 1968 18GF engine/cam/valves (all smog gear except PCV valve removed)
Stock HS-4 carbs / #5 needle
Jeff Schlemmer stock distributor, Crane XR-700 electro-optical points substitute and Lucas Sports coil.
NGK BP6ES spark plugs (plugs as shown below 1 to 4 , L > R )
Regular gas (Oregon-10% ethanol)

Around Town - 26-28 mpg
4th gear open road 30 mpg
O/D on interstate 32-34 mpg

And those who were seen dancing were thought to be insane by those who could not hear the music.
Nietzsche

Edited 3 time(s). Last edit at 03/06/2013 12:18PM by bobmunch.

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Re: MGB expected MPG? #19
crashbash david bash saint charles, missouri, USA 1968 MG MGC GT 1969 MG MGB MkIII 1970 MG MGB V8 Conversion 1972 MG MGB GT	Posted: March 06, 2013 12:18PM Registered: 1 year ago Posts: 40

I don't remember the exact numbers but I do know it was cheaper to run premium fuel rather than regular. Tested it several times, Tuned engine to each fuel and figured cost per mile

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Re: MGB expected MPG? #20
ClayJ Clay Johnston Mt. Olive, MS, USA 1972 MG MGB	Posted: March 06, 2013 12:55PM Registered: 7 years ago Posts: 7,353

My 72 w HC/fast road cam/HS4s/OD, I average about 27USmpg per tank. I tune my car over several tanks of gas. If its consistently under 27, I'll check plugs and lean the mixture.

As I've said before, if you put a group Bs on a exhaust analyzer, you would find many running rich. I know I was surprised by what the sniffer reported.

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