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MGB expected MPG?

Posted by n56545 
mac townsend Avatar
Fairfield, CA, USA   usa

I'd say a realistic range would be 18-35.

anything much over 25 I'd suspect of bad records/calculation or heavy highway miles.

a heavy foot shows up more prominently with the B. And it seems a lot of folks seem to believe one must keep the tach needle between 4 and 6 at all times.

And city driving also drags it down further than a modern car would see.

1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks:
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Jim K Avatar
James A. Krasnansky
Liberty, KY, USA   usa
1970 MG MGB GT "Chloe"
1971 MG MGB GT "Roscoe"
1972 MG MGB "Camilla"

I bought a '70 GT in 2010. I put 12,000 miles on it in a year. Mid-grade fuel, HS4's, OD. I average about 28 - 32 mpg. Got 36 on a couple 700 mile runs with OD on the Interstate. This '70 is the best running MG out of the 6 I've had.

Jim K is a grease-stained wretch
Starbuck Avatar
Monte johnjulio
Greensboro, North Carolina, USA   usa
1967 MG MGB GT "Toaster"
1974 MG MGB "The B"
1979 Triumph Spitfire 1500 "Shitfire"

If properly tuned:

Ethanol fuel will reduce your mileage 8-15%

Tire under-inflation can also affect it as can thicker viscosity oil.

Also how you drive is important. holding in a lower gear too long can really pull down your mileage but shifting too soon and lugging the engine can do the same.

I averaged 27-32 with my roadster over a 10 year period using straight 50wt oil.

My GT has averaged around 26-28 over the last 1000 miles though I do have some more fine-tuning to do.

Neither car has overdrive.

"...They say that a man with two restoration projects is a poor man...I now have three...WTF was I thinking!?!?!?!?!?!?!"

1967 MGB-GT,1979 MGB roadster, 1979 Triumph Spitfire 1500 1974 MGB Roadster (retired, giving its life to be a parts car)

My 1974 MGB restoration at:
My 1979 Spitfire restoration at:
My 1967 MGB-GT restoration at:
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Tom D
Cape May, USA   usa

my 71 with 32/36 weber non o/d pertronix ig, new plugs/wires/cap & rotor about 22mpg overall average--rebuilt head, new oilpump and premimum fuel .. most rides 50 miles or under, some 100 milers..I keep stabil in all my fuel as todays gas deteriates if it is not used within about 2 weeks of purchase.
Mike Keeney
scenic Fleetwood PA, USA   usa
1976 MG MGB

I figure on 18mpg as my average. 76 B, twin HS4 with AAA carb needles, desmogged, performance cam, no OD, I don't drive like an old man, it is for fun.
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mac townsend Avatar
Fairfield, CA, USA   usa

the only time I have ever seen premium fuel to deliver greater mileage was when I had a SAAB that would advance timing until it pinged and then back off. High test got about 10% better over about 5,000 miles.

Never saw that on any other car. Including the MG. The only way consumption would be affected is driving parameters or active engine tune adjustment and the B doesn't have the latter as the SAAB did.

It is true that if the car is having (perhaps unrecognized) detonation, then premium would probably reduce/eliminate that and that would affect mileage to the good. But that means the state of tune was inappropriate for the fuel. Correcting this should change the matter considerably.

1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks:
cdaubs Avatar
Charlie Daubs
Redding, California, USA   usa
1964 Jaguar E-Type "Snowball"
1970 MG MGB

My '70 got 30mpg when I drove it home from Las Vegas to Redding. A trip of over 800 miles. Not really sure how many miles are on it since it has been through a couple of owners and the speedo has turned over and the cable is now broken. But I think with proper tuning, good gas, and a light to moderate foot, you should get something close.
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ShickenChit Avatar
Toby Foster
Danville, CA, USA   usa

19.5mpg overall, Weber DGV 32/36, wider than normal "boy racer" Civic tires, 5 speed tranny, "hot street cam," California gas. I've never really messed with my timing, as my timing light died, and it seems to run fine except for being consumptive.
jim jensen
cleveland, USA   usa

...check the plugs.....and the points.......if plugs are black, then adjust the carbs......or go to ngk bp5 if fawn colour- to heck with it.....just enjoy the car........most here can afford a few bucks in gas.....
ourmg Avatar
George Heissenberger
Victor, New York, USA   usa
1973 MG MGB MkIII "OUR MG- The Old Girl"
2006 Mini Cooper "Greta's Mini"
2014 BMW MINI Countryman "Little Red"

1973 desmogged MGB with stock SU HIF's and I get 25-27 MPG like clockwork - have for decades.

"OUR MG" Glacier White 1973 MGB, owned since 1983. Factory hardtop. Member MG Car Club Western New York Centre
"Beer is proof God loves us and wants us to be happy" - Ben Franklin
spikemichael Avatar
Michael Caputo
Athol, MA, USA   usa
1973 MG MGB
1973 MG MGB "Freebie"
1976 MG MGB "B-4"
1979 MG MGB "MegaBeanie"
1989 Suzuki Intruder 800   → more

'79 Rubber bumper
no over drive
Weber 32/36 (DGEV)
stock internals
Peco exhaust w/ resonator at the back only
Consistent 28 MPG on 89 Ethanol 10%
25 MPG on 87 octane E10.

sniffer says I run lean.

Michael J. Caputo
'79 RBB and '73 CBB owner with extensive experience in 12v Audio System design and installation.
Vendor of Regalia and Promotional Products. Forum Member with a warped sense of humor.

Member Services:
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Rod H. Avatar
Amity, Oregon, USA   usa
1964 MG MGB
1968 MG MGB GT

I've always got about 20 in town and 30 on highway trips with my MGBs, with no overdrive. Got about 32 once with the roadster on a trip, and have sometimes dropped to 18 or so when the trips were short and the weather cold.

I can't understand why people are frightened of new ideas. I'm frightened of the old ones. John Cage

'63 MGB
'80 VW Vanagon Kombi
'09 Mazda 3 with 5 speed manual

gerry brinkman
nj, USA   usa

MkI - Overdrive - Supercharger;

Regularly get 25mpg - took a few tries to get the mixture and timing right
but now is perfect. Plugs are a nice malty colour, engine has good torque/power.

You may want to try an O2 sensor and a good gauge to tune the mixture.
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