Monday, July 26, 2010

Get better mileage - improving your fuel economy .

1. Your right foot

So simple anyone can do it. If you're caning it away from the traffic lights, you're wasting petrol and your mpg will be down. If you're endurance racing at 80mph on the motorway, you're wasting petrol. Here's the thing - your gas mileage can drop off as much as 15% between driving at or below 65mph and driving above 65mph. Now I love speed as much as the next person but you have to be realistic here - do you want better fuel economy or to get there marginally quicker? I sound like a total wet blanket telling you this of course, but driving slower absolutely will improve your mpg. Why? Because once you get over about 65mph, you're using more engine power to overcome drag, which means consuming more petrol to do it.
What about when you're not on the motorway? Well consider a little less braking if you can. If you can see the next set of lights ahead of you are red, don't race up to them and come to a complete stop. Try to moderate your speed a little if you can do it safely. If you can get there as they turn green and the traffic in front begins to move, you're doing OK. That's because it takes more energy to get you going from a complete stop than it does from a slow roll. So if you can do this, it will improve your mpg.
lower your octane

2. Change octane if you can

Too many people drive around with medium or premium gas in their tank when they just don't need to. If your owner's manual says "regular", it means it. Putting mid-grade or premium in is just wasting money. Why? Unless you have a high-compression engine which could be prone to detonation (pinking / pinging), you have absolutely no need for high-octane petrol. The only thing that higher octane gives you is less probability of detonation. In high-performance cars with high-compression engines, that means allowing the engine management system to work at peak efficiency but for probably 75% of you, your car will quite happily run on the cheapest petrol you can put in it. Not an improvement in fuel economy per se, but a money saving at least.

3. Use the internet

Again - not so much about improving your mpg as saving money; no matter where you live, there will be one or more internet sites that can provide you with petrol prices in your area. Vote with your money. Buy from the cheap ones, and shun the expensive ones. It's not improving your mpg, but it is saving you money, and in the long term, that's what counts here. Apathy in this area is what the petrol companies rely on. To get you going, here's a couple of examples. US petrol prices. UK petrol prices. For others, use your favourite search engine.

4a. Check your tyre pressures

This is a total no-brainer. Check your tyre pressures regularly - make it part of your sunday routine or something. All motoring sites and magazines tell you the same thing and that's for a reason. If your tyre pressures are low, you will be increasing the rolling resistance of the tyre on the road and that will be robbing your fuel efficiency - your gas mileage will be down. So make sure they're up to manufacturer recommended values (at the very least) and watch your mpg get a little better.

4b. Get low rolling-resistance tyres

You might never have considered this, but manufacturers do make tyres designed for low rolling resistance. This means that there's less effort required to roll the tyre along the road surface. Less effort means less load on your engine. Less load means better mpg. When I went for aftermarket alloy wheels and tyres on my Honda Element, my gas mileage dropped by about 1mpg due simply to the change in tread pattern of the tyres.
get rid of the roof box

5. Get rid of the roof rack

You go biking or skiing at the weekends. Great. When you're commuting to work, that empty roof rack is adding aerodynamic drag to your car. More drag means more power to overcome it, which means worse mpg. Take it off when you're not using it. Same goes for those 'aerodynamic' roof boxes - if you're not using it, get rid of it. Yes they look aerodynamic but the fact of the matter is they do induce drag. And to be honest, they look silly. Hey - I know it means getting up and doing something rather than just routinely getting in your car and driving off but we're talking about gas mileage here. mpg. Fuel economy. It's all to do with money. Be lazy? Or save money? 

6. Change your air filter

Out of sight, out of mind. I'm guilty of this. Your air filter is what protects your engine from ingesting all the dust, dirt and crap in the air. If it's doing its job well, it will clog up, much like the bag of a vacuum cleaner. Once it clogs up, your engine has a harder time sucking air through it. To compensate for the reduced airflow, the engine management system will richen up the mixture, using more petrol to keep the engine running smoothly. Replace your air filter once a year and you'll guarantee better gas mileage. So why am I guilty of this? At the time of writing I change the three-year-old filter in my car and my mpg jumped by 2.5 overnight. On my car that equated to a 13% improvement for an outlay of $14. Duh! This is one of the easiest ones to do yourself too. Go out to your local parts store and look through their catalog to find the right filter (or use any of a myriad of online retailer who normally have better prices on aftermarket and performance stuff like K&N air filters). It will normally be a simple matter of some plastic or metal clips to get the airbox apart and then you can replace the old duffer with the new hotness.

7. Change your oil and oil filter

Whilst you won't see any massive improvement by changing your oil and filter, you're ensuring that your engine is keeping its 'fresh blood'.

8. Get new spark plugs

Spark plugs work in an incredibly hostile environment. If you've got more than 30,000 miles on yours, change them. Fresh plugs that aren't covered in carbon desposits will certainly help you in your quest to become a fuel miser. 

9. Ultrasonic cleaning for your fuel injectors

The only surefire way to clean your fuel injectors is to have them removed and given an ultrasonic bath. This is like those jewellery cleaners you might have seen. Basically it's a small tub filled with detergent solution that is hit with ultra high frequency vibrations or sound waves. The net effect is that any carbon deposits are shaken off the fuel injectors. Clean injectors give a more even fuel-air mix which results in a more predictable burn in the cylinder, which will contribute to improved gas mileage. If your injectors have never been done, or you've got more than 60,000 miles on them, consider getting the professionally cleaned. It won't be cheap but it's cheaper than a new car (by a huge margin) and it will help your mpg.

10. Remapping your ECU - chipping and tuning

Expensive one this, but it might be worth investigating. For the most part, chipping or remapping your engine management computer would normally be done to improve performance. It is possible however to go the other way - trade off some performance in exchange for better gas mileage. Not a lot of places are advertising this yet but as the price of petrol continues to spiral, I wouldn't be surprised to see this happen. For example, a few tuning houses in America have seen some interesting results from flashing European engine maps into US vehicles. It's a bit dodgy because it means those vehicles won't pass the emissions tests, but if you're serious, you could get a dual-map system. For the inspection and emissions, leave it in "US" mode. For everyday driving, use the European map. Of course you didn't get that idea from here :-) 

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