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MG MGB GT V8 Factory Originals Technical - What's in the tank? Slipping out of reverse?

New V8 owner (cb ''75) little concerned at fuel consumption (4*) - not the cost, just the fact that something might not be behaving as it should. I'm getting about 180 - 200 miles to a tank with fairly judicious driving and have been told that the car should run rich. Can anyone tell me how that compares?

Also, the car slips from reverse when the engine is cold. Its fine when at running temperature. I have been told this is a fairly common flaw. Am I being strung a line?

Any help would be appreicated.

Richard Saunders
Richard Saunders

I have a R/B '75. Can get 27 to 28 mpg on 4star, touring on continental roads at a very steady 65 - 75.
UK 12 mile urban commuter run by my wife increases consumption to around 22 / 23 mpg.
Not using it at the moment so cannot comment on what difference Unleaded will make.
David Smith

If you have a factory V8 you should be using ordinary unleaded anyway, and it needs no adjustments.

180 to 200 miles on a tank is low, I could possibly get 250 or more, it frequently goes over 200 with still 1/4 left. This equates to 26 or 27 mpg, but it does include longer runs. If I have a spell of local runs it drops to about 21 or 22, i.e. type of use makes a huge difference.

Never heard of slipping out of reverse as being 'common' (it is the same as the 4-cyl car). But any gearbox with wear in particular areas will slip out of any gear.

Paul Hunt


My factory box was showing the sympton you write about
at about 130,000 so I had it refurbished - which solved the problem.

I am now running with a LT 77s box but the change is unrelated.

Your fuel consumption may be consistent with the state of the box - new needles/air filter cartridges/breather
filter and flame traps would be a good start - I get 20 - 22 mpg from a 3.9 (weak mixture/mixed town & long distance).

finally - if all else fails - use the car's performance and drive car the way the makers' intended - they can get quite constipated.


This thread was discussed between 28/10/1999 and 01/11/1999

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