It’s hard to believe that this fairly ordinary looking diesel powered family saloon, is so fast it has to be electronically restricted to a top speed of 155mph. Think that’s cool?, so do I, but what’s even more astonishing is that it will also deliver an average of 50 mpg on the combined cycle! Wow! – I want one! This Bmw 330d develops close to 250 bhp, will hit 60 mph in 6.2 seconds and then go on to its 155 mph top speed, but if you drive it in a sensible manner it will also return 50+ mpg! This is a revamped version of the most recent 3 series, which is now 3 years old. Performance and economy from the 3 litre diesel engine through the 6 speed gearbox fitted to the Bmw 330d is impressive to say the least. The 330d engine utilises Bmw’s third-generation common-rail fuel-injection system. The unit produces 247bhp and returns 49.8mpg in the combined cycle. The 330d delivers the bulk of its shove from very low down the rev range and will continue to rev well past 5000rpm, when most diesels run out of puff around 4000rpm. BMW has also revamped its original iDrive setup with a more user friendly version. Not much else has changed in the revamp, the interior is still a little cramped in the rear, if you need more space the Bmw 530d would be a suitable alternative if a little more expensive. The revised Bmw 330d is on sale now and prices start from £30,950, its closest rival is the classy Mercedes-Benz C320CDI, which is another great performance diesel.
This is the most common car type on UK roads today, although diesel cars with a manual gearbox will probably take the lead in the near future, still with me? It’s worth mentioning that in this type of car, with the exception of steep hills, you should never need to go over 3000rpm. Tearing up the gears, then cruising in 5th gear, is NOT driving for economy! I have tested all the fuel economy myths, the old method of the lowest revs in the highest gear, works quite well, (eg: 1500rpm in 5th gear) but there are other factors that you must be aware of. A method I like to employ, is what I call the Imaginary Rev Limit, where for instance on a flat road, starting from a standstill, you imagine that you can’t exceed 2000rpm but there is a rule you must apply to this method, and it is just simply, never let the engine struggle. If you are sitting at 1500rpm in 5th gear, and the car is chugging, or vibrating badly, then you have two options. Option 1: Increase your speed in 5th gear, until the car runs smoothly again. Option 2: Drop down to 4th gear to lessen the strain on the engine. Whatever option you choose, the engine would no longer be stressed. Option 1, would yield the highest fuel economy on a flat road, or a slight uphill stretch. This method does not take the engine ‘Sweet Spot’ into account, but it will serve you well if you can’t find the sweet spot. There was a time in the past when even I believed the sweet spot was a myth, but it is there, you will find it somewhere between 40-60mph in 5th gear (or 6th if you have a 6 speed box), in difficulty to find it’s similar to the G-Spot in women! If you have a mpg computer in your car, which gives an accurate reading in real time (a lot of them don’t), you should be able to see it, by varying your speed while cruising in your highest available gear. If you have a spare £100, you could buy a scangauge, you can find them on the internet, just google the name, it plugs into the OBD Socket found under the dash in most cars. It is much more than an mpg meter, and is extremely accurate, but probably only justifiable for a serious fuel economy nut like me. To sum up the sweet spot, I think it is accurate to say that it is a product of the torque characteristics of your engine, and is usually found at the peak point in the rev range where torque delivery is at its strongest, which is why it varies from car to car. Read the article ‘Driving Style’ for a snippet of knowledge on how to keep your engine running without using any fuel. What did he just say? Alright it was a little play on words, but the point I would like to get across, is that there are times when your car is using no fuel at all, and you can exploit that knowledge if you know when it’s happening.
I cannot stress enough the impact your driving style has on fuel economy. You must adjust your driving style to suit both, the vehicle you are driving, and the environment you are driving in. To get the best out of your car, you must first properly understand the fundamental driving techniques to use, but more importantly, WHY YOU SHOULD USE THEM! One obvious thing to mention at this point, is that although I will include tips for cars with an automatic gearbox, these articles are biased in favour of cars with a manual gearbox. There are many reasons for this, not least the obvious fuel penalty with a conventional autobox. If you can’t live without an automatic, there are CVT (Continuously Variable Transmission) based automatics, which offer little, or no fuel penalty over a manual gearbox. Please note at this point, that I won’t be covering petrol cars that are fitted with a turbocharger, as you would probably own it for all the wrong reasons!
I’m going to hazard a guess here, and say that around 90% of petrol cars on UK roads in 2008, have Electronic Fuel Injection or EFI, older cars used carburettors before EFI became the norm. You need to be aware that some of the methods your ‘dad’ told you to use, do not work so well in modern petrol cars. Cars fitted with EFI have something your daddy’s car didn’t have, A FUEL RETURN PIPE! Yes, quite simply put, it’s a pipe that will return unused fuel to the tank. Q: When does that happen then? A: Every time you take your foot OFF the accelerator. This is where most people make a BIG mistake, they start thinking that if they coast along the road in neutral, and keep their foot off the pedal, they won’t be using any fuel, …WRONG!!!!!! Here’s why. You’re driving along and you come to the top of a big hill, and you start thinking to yourself, I’m gonna freewheel down this and save some fuel, so you stick it in neutral and coast down the hill on tickover, WRONG AGAIN!!!!! WHY? Because, when you were coasting down the hill in neutral, your engine was ticking over, so it was using fuel, and not returning it to the tank! Now, at this point, you might be thinking, ‘but I still saved fuel’ and I would say ‘Yes you did ‘grasshopper’, but what you should have done at the top of the hill is this. – At the top of the hill you should have taken your flipper off the go pedal, and left the car in gear, now you should use engine braking to go down the hill, stepping down a gear or two to slow yourself, and a little foot brake if needed, or if it’s a big open road ahead, you could just have left it in 5th or 6th and gather speed. Why use engine braking, I hear you ask?, it just doesn’t make sense? – well it’s quite simple really. When you go down the hill using my method, if the car is still in gear when you take your foot of the accelerator, the engine will not be using any fuel, I mean NONE WHATSOEVER!, it just returns it to the tank. If you let the revs drop below around 1000rpm, tickover will kick in to stop the engine from stalling, and you will be burning fuel. Whereas, if you take your foot off the pedal, but keep the engine revs above the point (approx 1000rpm) where tickover kicks in, your car will not be using any fuel. The point of that example is to get you to use engine braking whenever possible, simply because it cuts off the fuel supply to the engine. When approaching junctions or traffic lights, work your way back down to second gear when possible, to keep the fuel supply cut off for as long as possible, but never shift down into first while the vehicle is in motion, I know 99% of you will know this, it’s just for the 1% who don’t know. Just one more tip for this section, on the subject of cold starts in the morning. When you start your car in the mornings for the first time, some of you will sit there for 5 minutes to warm the engine up. The almost traditional engine warm up, is a blatant waste of fuel, it is totally uneccesary and will play havoc with your mpg figures, driving off immediately after starting your engine in a non turbo petrol car is much more fuel efficient.
Edit: I came across this video made by a Jeremy Clarkson wannabe in the UK, its a bit nerdy but he makes a few useful points. Anyway Clarkson can rest easy and his job is definately safe for a little while longer.
A car buying advice request submitted by email to mpgtips.co.uk
Hi
Love your website!
I wonder if you could help me . . .
I’m looking to change my car to one which is more economical on fuel, however, I really want to stay with an automatic. I can’t seem to find an auto that has a decent MPG and wondered if you could help?
I have approx £8-9k to spend and am looking for a safe runaround.
Many thanks
J Littlewood
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Alan’s reply to the request for car buying advice.
Hi Joanne, I’m glad you like the site, I am currently compiling a searchable database of new & used vehicle info for the site, it should be ready in a few weeks. However, here’s a quick list of Brand New Cars
that may suit you, along with what you can expect to pay your local dealer.(more…)
Yes it normally does, but if you let the revs drop so low, that your engine starts chugging, or struggling in any gear, then that will hurt fuel economy. If it’s chugging, then you need to drop a gear, ie chugging in 3rd, you drop to 2nd. What you must understand is that, (more…)