Petrol Cost Cutting System Article Discussion Area

potbelly

Hi Martin,
Great article on fuel saving. I discovered Petrolprices.com last year and regularly save a few pence a litre by using a different local garage.
My only query about your ideas is that you recommend filling up when you get to a quarter tank left, so you aren't forced to fill up at an expensive garage. But later you say 'declutter your car to improve petrol consumption', presumably to reduce the weight of the car. What about the weight of a full tank of petrol? That will weigh considerably more than most people's car junk so wouldn't it be better to only half fill your tank? There's going to be a horrible mathematical formula to work out the best quantity but I am sure half a tank is better than a full one.

john1

Hi

https://www.petrolprices.com has been mentioned on other motoring web sites, whilst being very good there are apparently some errors like one service station mentioned had been closed for last 6 months. In my area the lowest LPG prices is actually 35.9 whilst https://www.petrolprices report lowest is 39p. So user beware!!

datimms

It is true that air con uses fuel consumption- it uses some engine power to drive the compression of the gasses.

It is also true that an open window will lower fuel consumption due to drag, as will roof racks, sun roofs, spoilers etc.

I don't know squat about how an alternator works, but I assume it's always charging the battery and using some engine power while the car is running, so therefore using electrical accessories wouldn't affect fuel consumption but the battery condition.

It would be interesting to discover what wastes more fuel- having a window(s) open or having the aircon on.

tjfs

The alternator will place a greater mechanical load on the engine if it's being asked to produce more electrical power so it's not correct to say that the additional energy is "wasted". Aircon definitely does put a heavy load on the engine - I remember hiring a Nissan with aircon, when you pressed the button you could hear the engine grumble about it!

Some more ideas:

- keep a notebook in the car and jot down each time you buy fuel (odometer reading, quantity of fuel) to work out accurate fuel consumption
- buy fuel frequently when the price is going up, let the tank empty when the price is going down
- try to do long journeys at night when the engine is more efficient and there's less traffic to hold you up
- choose a fuel efficient car when it's time to change, preferably diesel

And of course there are ways to do without the car - cycle or walk when you can, it gets you fitter and saves money too (cancel that gym subscription!) see https://www.sustrans.org.uk for routes in your area. Bikes can do the weekly shopping if you get a cycle trailer. If you cycle you can often park for free and much closer to work than if you drive, also your journey takes much the same time even if there is heavy traffic. Join a carshare scheme at work and take it in turns to give lifts. You can charge for taking someone in your car provided the amount you charge is no more than cost price. If you have more than one car in the family consider whether you could manage if you sold one - we did! For the rare occasion you need more than one it could be cheaper to hire a car.

Tim

samedan_2

It is best for the air con to have it running all the time. It will not affect your fuel consumption unless it is actually producing cold air. If you don't use it thru the winter you may find it won't work on the first hot day in the spring and repair bill will be a great deal more than the mpg loss from running it. It is claimed that the increased fuel consumption caused by driving with a window or two open may be worse than the increase caused by using the aircon.

fantasy222

The best tip I can give anyone on how to save fuel is
Get a Tom Tom or similar device. The cheapest Tom Tom circa £330
will tell you when to set of on a journey and will give you a running time of when you will arrive at your destination. As a couple of clowns who go to many different places to entertain, we never know how long it will take to get to our parties. Since we bought the Tom Toms we have saved hundreds of pounds on fuel. We no longer race from one party to the other only to find we are killing time when we get to the venue.
Take a tip get a sat nav and it will help you to keep the "pedal from the metal"

taurite

praven wrote:

I drive a diesel and I have a hypothesis that some diesels give better economy than others. I fill up with the regular diesel at either Sainsbury or Tesco and I am sure that I get significantly more miles per litre with the Tesco fuel. At this stage this is just based on a quick mental caluclation each time I fill up, and of course it could be influenced by the type of driving I have been doing.

I wonder whether there is some property of the fuel that the company has to publish that makes it possible to get some kind of measure of the economy to be had from the fuel.

I'm talking about as much as 5%.

Any thoughts?

Paul

I tell you what mate, I read somewhere that Shell fuel is the most efficient as they add alot of things to it. It said you should fill up once in a while with a decent fuel like Shell/BP as it is better for your engine. Now I always used to fill up with Sainsburys fuel as it was the cheapest near to me, tiht discounts etc. When I read this I thought I would give it ago as there was a Shell station nearby and was only maybe a penny more than Sainsburys or the same due to the proximity of the stations. I drive a Diesel and using Shell fuel gave me about 50 miles extra per tank!! I know only use the Shell fuel.

AndrewK_3

The article says, "This is also a reason not to overfill the car after the nozzle clunks, as any excess will go out of the overflow and is wasted."

Am I the only one who hasn't a clue what this means? I've never heard of an overflow - is this on the car or the pump? From what I've experienced, the more times I squeeze the trigger after the clunk, the more fuel I get, but the extra amount decreases with every clunk until the pump refuses to give me any more (or occasionally it doesn't work properly and overflows)

Does anybody have any more on this?

dixie_dean_2

How does the pump know your car's full? This has bamboozled my non-technological/mechanical mind for all of 3 months now. The nozzle must have some sort of sensor is my guess but it just looks like a piece of metal. Please help!

AndrewK_3

Well, I didn't know either, and it's a very good question, so I had a hunt around and found this, which answers both our questions. From http://www.theanswerbank.co.uk/Article1627.html

Q. How does a petrol pump nozzle know when to stop?
A. The nozzle contains a small pipe that constantly sucks air from the end because it’s connected to a vacuum at the end of the hose. When your petrol tank is full, and the nozzle is actually sitting in petrol rather than air, the pipe will suck this petrol through the pipe, rather than air, causing a drop in pressure that is detected by a valve, which shuts off the petrol supply.

So that's how it knows, and that's where the petrol wastage happens - it sucks a little bit back up the detector-nozzle. I suspect that very little petrol is wasted in this way, but hey - it costs an arm and a leg, so why waste any?

On a related note, praven says,

I am sure that I get significantly more miles per litre with the Tesco fuel

One possibility, given that praven is using a quick mental calculation based on the total bill, is that the "tank's full clunk" happens at different fill-levels for different pumps. I've noticed that my petrol gauge is higher when I fill up at Esso garages than when I fill up at my local Tesco's. If my gauge was different, I wouldn't see this disparity, and might think that Esso fuel was longer-lasting than Tesco fuel.

I'm not saying that this is definitely happening in praven's case, just that it's worth considering.