Doing the maths ... which fuel is cheaper

ALPINA Costs - Insurance, Depreciation, Oil Usage

Moderators: Charles, neil, D4

Post Reply
User avatar
Charles
Moderator
Moderator
Posts: 7633
Joined: Mon Jun 23, 2003 2:44 am
Location: Oxford

Doing the maths ... which fuel is cheaper

Post by Charles » Wed Oct 06, 2021 6:58 pm

Just completed an interesting calculation when it comes to using E10 unleaded or E5 super unleaded in my car.

Over quite some mileage, I have established that I achieve about 25mpg when using normal Shell unleaded and 28mpg when using VPower. However, the new E10 is reported to cut economy by 10% so I would expect to get 23mpg on E10 fuel.

I did the sums using the following data:
E10; 23mpg, £1.42 per litre
Vpower; 28mpg; £1.52 per litre

In simple terms, cost per mile for each fuel is as follows:
E10 = (1.42 x 4.546)/23 = 28.1p per mile
VPower = (1.52 x 4.546)/28 = 24.7p per mile

As an extra, running the numbers at 25mpg for E10 = (1.42 x 4.546)/25 = 25.4p per mile, which means that even if I don't experience a drop in economy using E10, it is still cheaper to run VPower

As such, I can now fully justify buying the more expensive VPower over Shell's "ordinary" E10 fuel as it clearly costs me less per mile whilst at the same time giving me full performance.

Win Win, I think :dance
Charles
Teacher of Chemistry and driver of ALPINAs - not necessarily in that order ;)
B3S Touring (49/116) - been to the moon and now on the way back!
Renault Grand Espace - not mine but the wife's!

hap
ALPINA
ALPINA
Posts: 4302
Joined: Mon Feb 06, 2006 11:22 am
Location: Scunthorpe, North Lincs

Re: Doing the maths ... which fuel is cheaper

Post by hap » Wed Oct 06, 2021 8:54 pm

Great analysis Charles
I don’t have any local shell to me but presume similar saving on esso and Tesco super?

User avatar
Charles
Moderator
Moderator
Posts: 7633
Joined: Mon Jun 23, 2003 2:44 am
Location: Oxford

Re: Doing the maths ... which fuel is cheaper

Post by Charles » Wed Oct 06, 2021 10:22 pm

hap wrote:
Wed Oct 06, 2021 8:54 pm
Great analysis Charles
I don’t have any local shell to me but presume similar saving on esso and Tesco super?
Apply different price per litre and mpg (as appropriate) and you can calculate your own numbers

For example, for Tesco use £1.32 and £1.42 with the same mpg figures and you get 23p per mile for 99 Momentum and 24-26p per mile for E10 unleaded.
Charles
Teacher of Chemistry and driver of ALPINAs - not necessarily in that order ;)
B3S Touring (49/116) - been to the moon and now on the way back!
Renault Grand Espace - not mine but the wife's!

---pete---
AL
AL
Posts: 147
Joined: Thu Aug 28, 2008 7:48 pm
Location: Northamptonshire

Re: Doing the maths ... which fuel is cheaper

Post by ---pete--- » Thu Oct 07, 2021 6:49 pm

Just out of interest Charles, have you compared this calculated mpg with the BMW readout mpg at any point of the hundreds of thousands of miles?

I'm just curious whether the onboard computer calculates within a reasonable tolerance or not.
_____________________________________
2008 BMW Alpina B3 Biturbo Coupe no.137
2003 BMW Alpina B3s Coupe no.16
2014 BMW 525d M-Sport
2010 BMW 320d M-Sport
2000 BMW Alpina B3 3.3 Saloon no. 213
1995 BMW 328i Coupe
1989 Ford Escort XR3i lux

CaesarBob
ALPINA
ALPINA
Posts: 4114
Joined: Tue Nov 20, 2012 10:37 pm

Re: Doing the maths ... which fuel is cheaper

Post by CaesarBob » Thu Oct 07, 2021 8:09 pm

Based on a selection of cars I’ve owned (mix of new/older and brands) I’d say the obc is usually optimistic by at least a couple of mpg
B3 3.2 TOURING #062

User avatar
Charles
Moderator
Moderator
Posts: 7633
Joined: Mon Jun 23, 2003 2:44 am
Location: Oxford

Re: Doing the maths ... which fuel is cheaper

Post by Charles » Thu Oct 07, 2021 9:09 pm

---pete--- wrote:
Thu Oct 07, 2021 6:49 pm
Just out of interest Charles, have you compared this calculated mpg with the BMW readout mpg at any point of the hundreds of thousands of miles?

I'm just curious whether the onboard computer calculates within a reasonable tolerance or not.
My mpg figures are based on full to full against mileage on the trip over quite a few miles and multiple fills. My OBC is currently showing just over 27mpg (long term) which is about 4% low against actual consumption over the same period.

Close enough in my book!
Charles
Teacher of Chemistry and driver of ALPINAs - not necessarily in that order ;)
B3S Touring (49/116) - been to the moon and now on the way back!
Renault Grand Espace - not mine but the wife's!

User avatar
Charles
Moderator
Moderator
Posts: 7633
Joined: Mon Jun 23, 2003 2:44 am
Location: Oxford

Re: Doing the maths ... which fuel is cheaper

Post by Charles » Fri Oct 08, 2021 8:38 am

Just to add, I tend to have a rough calculation running in my head such that if I have driven about 330-340 miles since the last fill and I refuel shortly after the light comes on at 50 miles range to go, then I typically put in about 55 litres which means that I am getting about 27-28mpg.

Slightly different with the winter set on as it improves to about 360 miles and 30mpg.

Either way, it's generally there or thereabouts ...
Charles
Teacher of Chemistry and driver of ALPINAs - not necessarily in that order ;)
B3S Touring (49/116) - been to the moon and now on the way back!
Renault Grand Espace - not mine but the wife's!

Jules Sunleu
ALP
ALP
Posts: 290
Joined: Mon Oct 14, 2019 11:58 pm

Re: Doing the maths ... which fuel is cheaper

Post by Jules Sunleu » Sat Oct 09, 2021 12:28 am

Great thread and totally agree Charles. Me and the Mrs use Super in our dailies too as better for the car and no more expensive for the reasons you have mentioned.
Alpina B5 E61 2005 Touring #007 Special Toy Malachite Green with Caramel Merino Leather. Quaife LSD upgrade
Volvo XC90 D5 2011 Daily
KTM 990SMT 2013 Summer Toy
Suzuki GSX1300R Hayabusa 2002 Summer Toy
Kawasaki ZX6R 1999 Summer Toy
BMW X5 F15 2014 30d M Sport Daily for the other half
BMW Mini R57 2009 Cooper Convertible Toy for the other half

Post Reply