Go further on expensive fuel

stumcgoo

While buying the super-fuel (shell optimax etc) does get you more miles/gallon (I though about 5miles/gallon) is the extra cost of the fuel is not worth it (10p/litre extra!).

Normal
40 litres = 8.8 gallons
8.8 @ 40mpg = 352 miles
40L * 90p = £36
£36/352miles= 10p/mile

super fuel
40 litres = 8.8 gallons
8.8 @ 45mpg = 396 miles
40L * £1 = £40
£40/396miles= 10p/mile So same deal in this case!

Maybe somebody can plug in figures from a car that measures mpg rather than my made up figures!

So what about Morrisons fuel vs Shell standard fuel (or any other expensive stuff vs cheap stuff)? Which will get you more miles/gallon? Is it the same stuff in which case we should buy the cheapest or is it true that the "supermarket" fuel does not have additives in it that makes your car run better?

Bob

Wig

I doubt you'd get any more measurable extra miles, I don't when I use Unleaded 98 Ron or 95 Ron. And in France it is just about the same price as the normal stuff.

To measure the difference with any amount of accuracy you would have to record your fuel use over about 5000 - 10000 miles.

Some suggest the reason for any noticed difference could be down to the supermarket pumps being set to deliver the lowest side of the allowed accuracy.

BenL

This did indeed used to be the case for my Pug 206GTi on Shell Optimax.

I haven't tried it on my SportKA but have the facility to do it on my fuel logging spreadsheet.

I have recently been using a Total garage near my office which is the cheapest but has given poor mileage compared to the 2nd closest Jet garage.

I'm going to do more tests on it as the cold weather has just has hit and the car sits idle outside the house in a morning warming up at the moment so this could contribute.

I didn't notice any increase or decrease using French fuel on holiday in the summer either.

Ben

wolvoman

I've been measuring since August and done about 5000 miles since then in my 2nd car. The first few tankfuls using Tesco 95 octane and the recent tankfuls using Tesco 98 octane.

Currently I am averaging about 42.5 mpg with the 98 Oct versus 41 mpg with the 95.

That means fuel economy is 3.65% better.

Tesco 98 is 4p per litre more expensive than the 95. So at current prices (87.9p for 95 Oct), the 98 Oct is 4.55% more expensive. Per mile, it is only fractionaly more expensive.

Interestingly, the same calculation last month when 95 Oct was more like 96p a litre, then the 98 Oct was only 4.16% pricier per litre.


There's not much in it I guess is the final answer.

avantra

BenL wrote:

...I'm going to do more tests on it as the cold weather has just has hit and the car sits idle outside the house in a morning warming up at the moment so this could contribute...

.

Ben

Warming your car in the morning is about 0 miles per gallon. Better to scrape the frost a bit and drive on this petrol!

lcharm

Hi guys first post on this website, thought i'd make a contribution.

It's not so much the fuel economy that is the benefit of superfuels, such as optimax (which is so far the best in my opinion), but the benefits to your engine as tests had been conducted with optimax where carbon deposits in the engine where significantly reduced than in normal unleaded (correct me if you think i'm wrong!). This can aid in your engine lasting longer- much longer.

Cheaper petrol from tescos/sainsburys etc... are cheap for a reason, there are a lot more impurities found which can be harmful to your engine due to inefficient fractionation at refineries or something like that. Not sure where and how they get there petrol, but it does seem like a leftover job, (i.e. all the crap that BP, esso, shell don't use.

I think the best options are to keep tanks full (rather than half) regularly from a major supplier in different and cheaper areas, which may involve a bit more travelling than ur local but ends up worth it. That and stop revving up 1st 2nd and third gears, get into 4/5th as soon as possible !!

Hope someone finds this info usefull!

jjames_3

> That and stop revving up 1st 2nd and third gears, get into 4/5th as soon as possible

That depends on the speed you're doing. In many cars, labouring in 4/5 at 30-40mph consumes more fuel than going around in 3rd gear, especially on an incline.

Think about riding a bike. Ride it slowly in a high gear and yes, your legs are turning around less quickly but you're sweating like a pig pushing the pedals down. That's what an engine's having to do in too low a gear.

Going on personal experience, the Hyundai 1.3 Alpha engine falls from 39mpg to 37mpg at 30mph going from 3rd to 4th around town.

iluvmylexus

i used bp ultimate diesel when it was first introduced, it was then priced at 3p per litre more than the standard bp diesel. on 40 litres i got about 40 miles more per tank full [from 230 to 270 miles per tank]. i also found better response from the engine and an increase in top speed of my work vehicle of up to 10 mph, [a very sluggish diesel automatic]. nowadays ultimate diesel can cost as much as 102p per litre (including 1p per litre for each nectar point) wheras i can purchase normal diesel for 90.9 per litre (esso)

Wig

wolvoman wrote:

That means fuel economy is 3.65% better.QUOTE]

No it doesn't because you have to do atleast 5000 miles on each fuel type. Having a couple of tank fulls of the cheaper stuff to begin with. Is not a useful measure for comparison IMHO.

tomstickland

Optimax etc is higher Octane rating, but actually has lower calorific value than 95 premium. ie: it contains less energy per unit mass.

Octane rating measures how suscpetible the fuel is to preignition/pinking/knocking. Calorific value measures how much eneregy per unit mass there is.

Anyway, higher Octane rating allows an engine to run more compression ratio or spark advance and so you get more energy out per amount of chemical energy put in.
So, some engines will provide a performance and/or economy advantage with higher Octane petrol.

However, I doubt that using Optimax or similar will provide any means of cutting cost.


With regard to revving, most engines are most efficient when under about 40% load at around 3000rpm. Labouring it a low rpm is just as inefficent as revving the tits off it.

Another interesting thought that people often debate: is it more efficent to accelerate rapidly for a short period of time or to accelerate gently for a long period of time.

Speeding up and then slowing down via braking etc is very wasteful since you're throwing momentum away. Speed is also wasteful since drag forces increase with speed.

Most modern cars let themselves down by being too heavy and large and having wasteful tat like air con etc. Weight is possibly the biggest enemey to efficiency, closely followed by frontal area.
A 600KG proper mini or a 500KG kit car would both make very economical cars.

shown73

Survey was done a few years ago, which found that fuel supplies were exactly the same for supermarkets and main stream garages, in some cases even delivered by the same tankers. All else is, frankly, bull.
Supermarkets can afford to be a bit cheaper, since their main aim is to attract customers for their grossly overpriced groceries. They are not losing money, just cutting the margins, partly through lower overheads.
That said, I have had some problems with my local Asda, but that is more down to water ingress in storage that any difference in quality. Also, my Mondeo handbook specifically recommend 95 octane standard brew, and that is what the ECU is set up for. So, buying anything more expensive is, presumably, a waste of money. Anyway, at 105,000 miles, with no oil between changes, and faultless running I must be doing something right.