Smiles per gallon and road trips in an Exige 350

[Jamesmitchell]

After 24 years dreaming, I've finally been able to buy myself my first Lotus, an Exige 350S. Almost immediately after taking possession, we entered a tier 5 lockdown meaning the car is now more or less grounded. But in the 500 miles or so I've managed to get out in it, I've become no stranger to the petrol station forecourt. With ample time on my hands now to plan some mega road trips for the spring, I've been wondered about MPG. More specifically, I'm curious to get opinions on whether there's much of a fuel saving to by made by sitting at 65-70mph (2400-2500 RPM) on the motorway versus getting into the outside lane and going with the flow. The latter would definitely be my preference just to reduce the tedium of the boring parts of the journey. But if it's going to significantly increase fuel consumption, stops and the petrol station and consequential delays to my journey, I see no point.

To reassure readers of this post that I have indeed bought the right car and am not better suited to a Prius, I will of course be planning my drives to take in the most enjoyable and scenic roads where possible. On such roads I regard fuel consumption to be of no object. There are, however, always going to be those potentially long stretches on a decent journey for which there is no alternative to a motorway slog. So really this is a question of Smiles Per Gallon - do I (a) sit quietly in the slipstream of a van on the inside lane because of the huge fuel saving I will make or do I (b) get in with the outside lane traffic and have a marginally less frustrating journey in the comfortable knowledge that it's not going to make a massive difference to the number of petrol station stops I have to make? Is there an optimal speed?

 

[Bibs]

Being a sports car, an Exige is aerodynamic so fuel consumption isn't really improved by slipstreaming. I doubt you'll notice the difference in real terms in fuel consumption cruising on a motorway, it's mainly affected by how hard you accelerate. 

[KennyN]

Hi James, First of all, congratulations on realising a dream, nice choice 👍

I have found that driving normally (with the flow) returns around 28 mpg on a decent run.  That soon takes a hit if you're pressing on, but it is what it is.  I don't think it's that bad for a 3.5L supercharged V6.

I cannot imagine that drafting a truck in the left lane would significantly improve the consumption, but I've never had the patience to try  I think the relatively small tank gives the perception of poor mpg, but it's the right foot that makes it a reality!

[Jamesmitchell]

Thank you Bibs and KennyN for your thoughts. I feel reassured that I can drive as comes naturally. 

[RoflOnMyWaffle]

I don't understand why people want to sit below 70mph to save fuel.

Firstly if I remember right, Mythbusters tested the drafting theory, you have to be within a foot or so for it to work, and the gains were pathetic vs the risk!

Secondly, just drive and enjoy, when she says empty you fill her up, rinse and repeat.

I know people who stress about mpg and it drives them mad when they "lose" mpg.

You can get mid to high 20s effortlessly, or really try and get high 20s consistently - meaning probably 2mpg difference, which over 3000 miles (arguably 15 tanks and the average Lotus annual mileage it seems) thats £40 odd. 

Can you be bothered to risk that, and not have fun, for £40 worth of fuel, in a car designed for driving over all else?

[Jamesmitchell]

3 minutes ago, RoflOnMyWaffle said:

I don't understand why people want to sit below 70mph to save fuel.

Firstly if I remember right, Mythbusters tested the drafting theory, you have to be within a foot or so for it to work, and the gains were pathetic vs the risk!

Secondly, just drive and enjoy, when she says empty you fill her up, rinse and repeat.

I know people who stress about mpg and it drives them mad when they "lose" mpg.

You can get mid to high 20s effortlessly, or really try and get high 20s consistently - meaning probably 2mpg difference, which over 3000 miles (arguably 15 tanks and the average Lotus annual mileage it seems) thats £40 odd. 

Can you be bothered to risk that, and not have fun, for £40 worth of fuel, in a car designed for driving over all else?

Well exactly - the car is there to enjoy and I don't think for a second a few extra MPG is of any concern. And definitely not concerned about numbers in the mid 20s. But without having had the luxury of a long drive and with a supercharger right behind me making a lot of noise of the motorway, I did get to wondering if I were looking at a few MPG or a hell of a lot MPG. I'm reassured there is nothing to worry about. Thank you.

[Bibs]

Being light also helps a lot with fuel consumption if it's a worry. Put your foot down and make some noise safe in the knowledge you're having fun and getting better MPG than a Discovery

[Jamesmitchell]

Just now, Bibs said:

Being light also helps a lot with fuel consumption if it's a worry. Put your foot down and make some noise safe in the knowledge you're having fun and getting better MPG than a Discovery

😆A Discovery is literally my other vehicle. 23 mpg.  

[Bibs]

[paul lodey]

Might be worth considering fitting a larger tank, I had one fitted to mine and it is much more convenient.

[duncx]

I checked my 350 Sport over 3000 miles and for every tank full of A and B road driving it did near spot on 25mpg. I also checked it on a couple of long motorway journeys sitting at a contant-ish 70mph (I'm really not interested in speeding on the motorway!) and both times it did 29mpg, which was areal surprise to me.

I'm sure that the faster you go the less mpg you will get but no way would I sit behind a car/van/lorry in an attempt to improve consumption - cost you more in stone chips  

Well done on your purchase by the way, you will love it

 

[Ali tuck]

How about seeing how little mpg you can get -it’s all about that 2nd and 3rd gear acceleration 🤣

[pete]

As a matter of interest how small is the tank

[KennyN]

18 minutes ago, pete said:

As a matter of interest how small is the tank

43.5L according to Lotus.

[fjc27]

Lotus website claims 40 l for sport 350 (and previous models as far as I know), 43.5 l for sport 410 (strange, it must be 48 l ?), 48 l for sport/cup 380 / cup 430

Have latest sport 350 models been upgraded to 43.5 l ?

[KennyN]

Apparently so....

[fjc27]

It looks like it is not the same in France 🤣  I suppose  it's a typo (Sport 410 also, 43.5 l )

 

 

 

 

[KennyN]

I blame Brexit 🤣

[Jcx]

Congrats!  Soon after getting my 410 I did a 2k mile trip through france to spain and andorra and was pleasantly surprised by economy.  I planned the trip to stop every 100 miles or so to fill-up so that i would rarely be below a 100-mile range such was my concern about running out.  By the second half of the trip we relaxed a bit.  With a few 10-hour driving days the car was also very comfy.  18mpg on the mountain roads and 30mpg+ on the dual carriageways.

[GFWilliams]

Congrats on the new car!  If you can stretch to it, the 60l tank from pro-alloy makes road trips a lot more enjoyable. In fact, I was finding that I needed a break before the car needed fuel on the last road trip I did...

[Jamesmitchell]

2 hours ago, Jcx said:

Congrats!  Soon after getting my 410 I did a 2k mile trip through france to spain and andorra and was pleasantly surprised by economy.  I planned the trip to stop every 100 miles or so to fill-up so that i would rarely be below a 100-mile range such was my concern about running out.  By the second half of the trip we relaxed a bit.  With a few 10-hour driving days the car was also very comfy.  18mpg on the mountain roads and 30mpg+ on the dual carriageways.

This is exactly how I plan to use the car. Good to hear it fits the brief. 

[Rolf]

Fuel consumption economy is better in the 410, needs 10% less fuel than my former Exige S in comparison. Maybe an excuse for an upgrade in the future