Petrol saving advice Needed, More MPG

blah_2

OK, Got a question on behalf of my dad. figured here would be the best place to ask

He`s recently brought a BMW 730i with a stupidly big engine that drinks petrol at a ridiculous rate.

After a quick search on the internet i found limited information on "Fuel Saver" Devices.

However i couldnt fine any real usefull information or recomendations

Car is only used lightly to and from work via motorway and around town

any advice apreciated (other than buy a new car)

Thanks

Vic_980

Not sure what you mean by Fuel Saving devices... would be interested to have a look if you post some links.

Has the car been serviced regularly? Changing things like spark plugs, air filter etc will keep it running better and help reduce fuel consumption.

JimArnold

Given the pressure on car companies esp in the USA to improve fuel consumption I would be very surprised if any of these devices work - there are certainly many hoaxes out there
They would also probably void any warranty you have

As said make sure it is serviced and drive it gently!

Driving style can double your MPG !

Kepp to 55 mph and don't accelerate too quickly

BobToo

There are various devices out there, the one in question is probably the magnet that goes around the fuel lines. TBH the manufacturers would fit these devices if they worked.

MUDGUTS

When you are dealing with a car like this, you need to do several things to keep your fuel consumption down.

(1) Correct tyre pressures, regular servicing, etc.

(2) Driving style: You need to drive with a very light right foot and imagine you have no brakes, so to speak. In other words don't hammer up to a junction with traffic lights at red, then brake heavily, only to accelerate away when they change. Anticipate traffic flow and use your head so that the car is moving steadily as much as possible much in the same way drivers of HGV's do. Think about momentum and how to preserve it.

My wife has a 2.5 Litre Auto. We drive that in this way and get around 25 MPG around town. There is certainly a 'knack' to driving for economy and once you get it your fuel costs will drop. Some people would recommend a diesel for just about everybody but I don't agree: Servicing costs can be high compared to a petrol and the first time you run a diesel after mistakenly filling it with petrol your fuel savings for the next decade have gone out of the window.

You could join something like www.lexusownersclub.co.uk and ask about driving style there (the Lexus LS 400 is a 4.0 V* engine with auto gearbox and a big car.)

Don't bother with so called fuel saving devices, they affect your brain and will convince you that you are using much less fuel. They are a tax on the stupid.

alanrowell

blah wrote:

He`s recently brought a BMW 730i with a stupidly big engine that drinks petrol at a ridiculous rate...
Car is only used lightly to and from work via motorway and around town

Engine is going to spend most of it's time getting hot enough to be efficient therefore I doubt there's little to be gained from a better driving style, fuel saver devices or whatever.

So either put up with it, change daddy's lifestyle so he doesn't do so many light journey's or get a different car.

My current car does 60+ to the gallon BUT I don't use it on short trips nor do I use it just to do one thing at a time (eg go to DIY, go to shopping) but combine several trips together

rdwarr

If he's going to keep the car for a few years an do lots of miles then an LPG conversion would be money well spent. I have a 3-litre Lexus which I bought 5 years ago and have done 60,000 miles in (at around 20mpg). An LPG conversion would have saved me between £4-5000 at today's prices. I wish I'd done it!

samedan_2

SFAIK an engine runs at its most economical when using the rpm at which maximum torque is produced; these days this figure can usually be found in the owner handbook. It usually equates to about 65 mph in top gear. I don't think that any fuel saving device works as advertised; many have been forced to change their adverts as they cannot provide acceptable scientific proof of their claimed benefits. A light right foot and minimal braking are a good start!

Silent_Bob_3

NOI but if he can afford a BMW730i he should be able to afford to run it. If he can't heavens help him when it comes to servicing etc. If he wants better MPG he should buy a smaller engined car or drive with a less heavy right foot

funky-footprints

my husband has a Audi S8 4.2, and paid £1,000 to have it converted to LPG. it is so much cheaper to run, and means he can afford (just) to have his dream car !! Ive a diesel 2.5 Tdi and have never filled it up with petrol !!

tomstickland

NOI but if he can afford a BMW730i he should be able to afford to run it. If he can't heavens help him when it comes to servicing etc. If he wants better MPG he should buy a smaller engined car or drive with a less heavy right foot

You can buy 2nd hand 7 series for very little money.
The problems are:
-heavy car
-6 cylinder engine, more mechanical losses
-round town driving is the worst for mpg

I drove a 1990 BMW 320i for a month or so and couldn't beat 25mpg no matter how gently I drove it. It wasn't in the best health though, some people claimed high 20s from this engine. 6 cyl engines have about 50% more frictional losses than a 4 cyl engine. I've got a 4 pot BMW now and manage 32normally and 40mph on a run.

TBH if the fuel costs are unacceptable i'd suggest going for a smaller engined car, around 2.0L and ideally a lighter model.