Which fuel

[Geordie]

Hi all
I will begin by apologising,,,I’m sure this topic has been covered before,but I’m crap at finding things on this forum,,,,I normally run my 91 m100 se on E5 fuel ,but was wondering if running it on E10 for a day or two is a problem or is there additives you can use to counter act the difference ,I live in UK north east
Cheers in advance

[FunElan]

a day or two won't harm you. Run the best fuel you can get. It's a performance car, it deserves it

[exeterjeep]

I'd only put E10 in as a last resort if no good stuff was available and I did not want to push it home, and then top it up with E5 as soon as possible. Certainly would not leave E10 in for any extended amount of time. Keep some E5 at home as we use it in the quad bikes/mowers.

[robertE]

I was chatting to a friend today who has an older car than my M100, and says he always uses Lead Additive, as well as E5 fuel . . . any thoughts?

[Tuga2112]

I was chatting to a friend today who has an older car than my M100, and says he always uses Lead Additive, as well as E5 fuel . . . any thoughts?

as time goes by and this question gets repeated, i get more and more arrogant on my view.
ive been running E10 since the day it came out, originally under the assumption that the government wouldnt allow something drastically damaging from being widely sold.
then i looked into all the information about it, and there was a lot of conflicting information with only 2 things that seemed a consistent "consern" this was increased fuel consumption (however no one could agree on a value) and fuel lines premature deterioration (theoretically likely but only for "older cars" due to rubber manufacturing practices which no one could put specific dates against).

the cost of E5 is more than 10% than the going price of E10... and I Personally found myself with an increase of more than 5% on consumption just from having the base timing changed back in 2016 after changing the head gasket. the change from E5 to E10 gave me a wopping loss of about 1 maybe 2 MPG... (or maybe im just more enthusiastic driving as i get more confident about my own maintenance work?)
since i am not running distances of more than 200 miles between stations. i think its ok to stop an extra 5 times a year to save the money. the increased consumption sure aint gonna make me call the AA

as far as fuel pipes.... they are already 30 years old, they will give up due to age long before "increased wear" gets to them...(if) and when that happens, my pipes will be replaced with whatever rubber compound is resistant to E10... making it outlive me anyways.

obviously, got someone who drives their m100 less than 500 miles a year, using E5 is not a hit on the wallet... in my case. the tank gets topped up more than onse a month

[Simon_P]

The Elan was designed to run on 95 RON fuel - premium unleaded in the UK, E5 or E10 is at least 95RON

Ethanol as a fuel has less energy per litre than "petrol" so fuel with 10% ethanol has proportionally less energy and will do less MPG. It is also an octane improver so the base fuel can be worse/cheaper as the ethanol improves its performance.

The stoichiometric AFR for "petrol" is 14.7:1 but for E10 it is 14.1:1 so for an open loop car it will run a bit leaner - difficult to say if that's better or worse but it is likely to improve MPG and reduce HP which you compensate for with your foot. There is a knock sensor so if it is too lean the ecu retards the ignition.

To a certain extent the ECU learns the characteristics of the fuel, so if you usually use 95 RON you wont see the benefits of 98 RON

If the CO pot is adjusted for the fuel most of the difference will be tuned out, but on a closed loop car the O2 sensor will adjust for the fuel only while it is closed loop ( open loop may be the way to go!)

You are unlikely to notice the difference - it is a matter of personal choice - I use E10 from Sainsburys in the Elan and the best/closest to petrol I can buy for anything with a carburettor

[Simon_P]

nder the assumption that the government wouldn't allow something drastically damaging from being widely sold.

Cor you're brave I wouldn't trust them to boil water.
You've probably not heard of Formula Shell then!

[chrism]

...agree with Simon_P, except petrol is a 5-carbon-and-more chain chemical and the octane rating (I think) is the amount of 8-carbon-chain bits in it so adding 2-carbon-chain ethanol shouldn't improve the octane rating but might raise the combustion temp a little (? causing pre-ignition/pinking?) since smaller C-chains are more explosive; eg meths/methanol is a 1-C molecule and ethanol is 2-C. I suppose 10% less carbon means less CO2/CO gases out of the exhaust is the idea.

Also I may be wrong but I treckon 14.1 (air) : 1 (fuel) is richer? than 14.7:1 so fuel consumption ought to increase? (imo) I dunno if more power will be noticed amongst those changes. They didn't worry too much about over-richness in the '90s; it might have made the car a bit faster but petrol was so cheap...and no-one worried so much about MoT pollution tests then, did they?

Again my opinion but there's nothing special about the Isuzu engine in a light, plastic car; it was probably fashionable for Lotus to specify whizzy Concorde oil and special MXV tyres etc but I reckon that was to make it 'posh' and 'racy'. We all use normal tyres and normal oil (perhaps synth) now so why not use normal fuel - as Tuga suggests?

Like the pink/blue coolant discussion it depends on how happy we are with what we've got - and how we like to preserve our m100s.

[Simon_P]

I'm no chemist but - The Octane bit is the reference fuel iso-octane, at the point which the fuel under test starts to knock being equivalent to % iso-octane in the reference fuel ie 95 RON is 95% iso-octane and 95 Ron Fuel can be anything that exhibits the same knock characteristics under test conditions.

Also I may be wrong but I treckon 14.1 (air) : 1 (fuel) is richer? than 14.7:1 so fuel consumption ought to increase?

You are correct that it is a richer mixture but the Stoichiometric AFR is the 'ideal' mixture so if the ECU has a table based on Petrol at 14.7:1 and the fuel being put in is E10 at 14.1:1 - The E10 at an AFR of 14.7:1 is lean.

Fully Synthetic and original Blue coolant both changed religiously!

[Geordie]

Hi guys
Thanks to all for reply’s (some a bit technical for me ) a simple yes or no would have sufficed,,anyway finished trip (1250mls) used E5 apart from one fill which I added additive ,averaged 36mpg and found no difference in performance ,,obviously don’t know how fuel lines etc enjoyed it or not ,but hey ho ,,like people say they could be 30 years old anyway so could be due a change on age alone
Geordie

[Simon_P]

a simple yes or no would have sufficed,

oh ok No then. Lotus say that the M100 is not compatible with E10 - does that help

I was chatting to a friend today who has an older car than my M100, and says he always uses Lead Additive, as well as E5 fuel . . . any thoughts?

lead replacement additives serve no purpose in the M100 which was designed to run without leaded fuel.