Dr Dave

hey, DD have you been on the sauce again , im sure you made a bit of a fopar here mate, where you said "remember at 0mph your getting 0mpg"

thats not true mate...at 0mph your still burning fuel (unless you have turned your engine off) and if you were doing that it would not be valid anyway, so 0mph is very high mpg (respectivly on a journey, when your moving also)

your mpg figures are quite good as you have a monster petrol engine

cheers mate.

DD_545i

I don't have to drive the rush hours as I work from home. So I don't spend a lot of time stationary. My actual average is 13.3L/100km since October 2008 when I got the car, and that's about 21.2 UK MPG.

parmblagan

parmblagan

no

parmblagan

no problem mate, i just found out that one of my old friends works as a tech at my local BMW dealer, i have spoken to him and he says his taking my car in as his own. he will check it out for me on his lunch with one of the other tech guys and get a full report on it by putting onto the dealers computers.

then if there are any parts that ned replacing he can do it for a fraction of the price.

the car goes in some time next week and i will let you guys know what it comes back with

mini_me

parmblagan

LOL

Dandle

Im not so sure 21mpg isnt unrealistic around town on a 6 mile journey(if its in traffic). My 530d needs about 4 to 5 miles before its warm enough to return good mpg. If your starting and stopping during that time as well then the mpg will be low as DD said. The diesels really need to be warm and be on a run to give good mileage. My 530d only does 10 mile work journeys and will return about 30mpg on them Thats not driving efficiently/slowly but it is all dual carraigeway with only a few traffic lights and no traffic. If I get it on a motorway though I can easily see into the high 40s or low 50s. Don't forget these are nearly 1.8tons of car and stop start traffic will hammer the fuel.

Dr Dave

ok, try this one........

what i was saying is MPG is not a measure of distance (in this case miles) its a measure of fuel used (by the engine) so even when a car is stuck in traffic, or driven hard, it gives a MPG figure (nothing to do with how many miles you can travel for your gallon) its a misnomer
MPG is a measure of how "frugal" an engine is, how "thirsty" it is, and the miles is just a by product, as in every day life you will come against traffic motorways and every thing inbetween, but the engine is the "constant".
they should rename it energy or output per gallon
static generators use fuel, but as they have no wheels, they are not classified as having MPG, because no miles at all can be racked up.

so your car would not be a 40mpg car if stuck in traffic...it would be a genuine 20mpg car because its still working....a smaller engine car or a more fuel efficiant engine also stuck in the same traffic would produce better MPG there is your comparison with better or worse MPG figures.

DD_545i

Fair enough if we take our engines out and put them on a test rig and have them maintain certain constant speeds, we can see how frugal one engine is compared to another. Again though, that's not what this thread is about. This thread is about basically "my car is giving bad MPG in town, is there something wrong with it" and the fact that we can't answer that because there's no such thing as a constant "around town". We need specifics for a comparison.

We can give an answer to similar, but crucially different, questions like "At a constant 70mph on the section of M1 between X and Y, and with only one 180 pound driver and no luggage and not a windy day with dry road, my car only gives me 35MPG - is this bad". Then any one of us can repeat the same test and say yes it is bad, we got 45MPG. It's the same reason the government figures for MPG are done at test tracks and not on the road. It'd be slightly unfair if they tested a BMW for it's urban MPG in London and then did the Mercedes test in some sleepy little seaside town.

So when the OP asks is my twenty something MPG figure in urban driving bad, we don't want to be answering yes it does seem bad because some of us are managing thirty something MPG in urban driving, that's a bad answer. The question should be responded to with other questions, like has it suddenly changed recently? is someone syphoning your fuel? are you experiencing more or less traffic jams than usual? has your driving style changed? are you looking at the trip computer's dynamic mpg figure? are you calculating it from your fill-up costs vs how many miles you got for that tank?