318 IS/I M40/42 MPG and running costs

[NickThompson89]

Hi guys,

I'm Nick, i've currently got an E36 328IS.


I'm having my salary cut soon and to be honest i'm struggling a little with the mpg of the 328. I have always wanted a red E30 318 coupe so I was hoping that you folks could fill me in on some running costs such as average MPG, MPG on a motorway drive, how many miles to a tank and how many miles to twenty quid?

Thanks in advance,

Nick

[adam_2922]

On a combine run. Motorways and short journeys with a pretty heavy food i have been getting about 29mpg from my 318i convertible (m40)

[iceox]

petrol bmw's and mpg dont really mix well

[broadie]

Hi Nick
I picked up my 318 touring (m40 with cat) the other day.
Needed a good service and the tyres were at 20psi. 100 miles down the A303 doing 80 where I could it managed 30mpg.
So I'm hopeing by the time I've gone and serviced all fluids and fetteled a bit, tyres at 35psi added some BG44K to clean out would like to see 40mpg but not gona hold me breath!

Maybe advance the ignition a bit if possible(but it all seems fixed) and a decat?

[Brianmoooore]

A M40 engined E30 is going to return around 30 MPG overall in normal mixed driving.
A DIY LPG conversion can be done for £250 -£300 with some careful buying of old and new parts. This will give you the fuel cost equivalent of about 45 - 50 MPG.

[broadie]

So whats the best engine for fuel in an E30 or that can be fitted without going oilburner Brian?

[ross_jsy]

I would say an m42 (318is, 16v 4 pot)

[dirtee-herbert]

i have always wondered what the most economical engine would be for and e30 conversion. i have read in a few places that the m42 318is is alot better on the juice than the m40 engines.

[TPS]

It is, I've done that conversion.

[G-Bear]

My IS (M42) I thought was pretty good on fuel not sure on MPG but if you drove conservatively it made a difference.

Sorry for the quick highjack...:

A M40 engined E30 is going to return around 30 MPG overall in normal mixed driving.
A DIY LPG conversion can be done for £250 -£300 with some careful buying of old and new parts. This will give you the fuel cost equivalent of about 45 - 50 MPG.

What do you get from your M20 on MPG.. Do LPG conversions still save you fuel on short drives? like 15-20 minutes.

[AndyTB]

Yea, my 318iS (M42) is good for 40mpg on a run if i keep a light foot. To be honest, it doesn't go really really low if i have a heavy foot either!

[Nick45]

M42 engined 318iS is significantly better on MPG than 316 and 318i (and obviously better than 320i and 325i). Only one I haven't had is a 316i but I would still bet the iS is better than that because it's a much more modern, efficient engine.

[magpie]

the 318is has a twin butterfly throttle body,you can feel the second larger one open on the accelerator pedal so if you just keep it on the smaller one [if you can resist the almighty m42 poowah] you'll get around 35+ mpg round the town .

[Brianmoooore]

What do you get from your M20 on MPG.. Do LPG conversions still save you fuel on short drives? like 15-20 minutes.

A running on LPG should give slightly more miles per kilogram than one running on petrol, since LPG increases the engine efficiency a little, but, since we buy car fuels by volume, and LPG is considerably less dense than petrol, the miles per gallon are reduced by around 15% - 20%. This could be improved by modifying the engine to optimise its performance for the new fuel (timing, compression, etc.), but this would compromise its ability to run on petrol as well.
I get around 27 MPG from an M20 E30 on petrol, dropping to around 22 MPG on propane.
If your LPG set up is of the old type mixer sort, you can obtain very real gains on short journeys. LPG doesn't need warm up enrichment like petrol does (LPG doesn't condense back to a liquid in the cylinders), so you can change to LPG immediately in summer, and within a minute or so in winter, eliminating the horrendous rate of fuel consumption, oil contamination and engine wear, that petrol engines exhibit until they are hot.

[NickThompson89]

Thanks very much for the replies so far. The LPG conversion sounds appealing. Where can I find more information on the DIY conversion.

[polsta]

best thing about the M42 is , is that the immense power doent really kick in until after 3500-4k RPM, so normal pottering about keeping it light acceleration and revs around 4k or under, it can be good on fuel, and it is quite revvy after that , yet not overly guzzly from 4-8k, for the times you want some fun, coupled with the nice interior and styling and sports suspension, make it a good e30 for all round daily use

[stew72]

I used my m40 318 cab as my daily for most of last year and got somewhere between 35 and 40 as an average.

[broadie]

Intresting replys would the M44 be as good as the M42 on fuel ?
Had an LPG volvo 850 years ago it was good but became a pain looking for fuel every 200 miles down this way as it only had the spare wheel tank.

[polsta]

Intresting replys would the M44 be as good as the M42 on fuel ?

remember the is a more revvy and immensley more powerful engine

[bmw9818]

how on earth have you lot managed to get 30-40 mpg out of an m40!

I used to get mid 20's on a good day and high teens when i used to cane it!

[Brianmoooore]

how on earth have you lot managed to get 30-40 mpg out of an m40!

I used to get mid 20's on a good day and high teens when i used to cane it!

Presumably because yours was way out of tune. It's easy to waste fuel.

[TheDutch]

I've been averaging 39.5mpg over the last few months commuting in a 318is to London. Much motorway and little desire to get to work. Have managed about 520 miles out of a 55l tank before, I think it was over 45mpg. I tend to drive slowly on the straight bits.

[iceox]

its all down to how you drive i sappose, but why buy an e30 and drove like a grany everywhere, go get a smart car for that and have the e30 for weekends.

i get 250 miles out of a tank with my 325 and i dont give a shite lol

[broadie]

Shit man please I beg you dont tell the e30 rozzers I drive every day

If I wanted something for the weekend that drink's fuel I'd have bought a boat

[811]

as iceox says, it's how you drive it.. i don't find the is to be much better on fuel than the 325.. 26/27mpg compared to 22/23mpg.. but i am on twisty B roads 90% of the time!.. i'm sure i could get more mpg if i tried though.

[broadie]

Its not about driving slow it about holding the corner speed so you don't need a load of throttle after the corrner. My mate was getting about 36mpg from a 2.7eta manual with a high ratio diff E30.
Stay off the brakes they only slow you down.

[Brianmoooore]

Stay off the brakes they only slow you down.

Exactly! Every bit of heat dissipated by the brake discs is energy that was produced by burning fuel a few seconds earlier. On public roads it entirely possible to move along swiftly without hardly ever using the brakes. Just keep them for the odd sharp bend and emergencies.

[broadie]

And its fun holding your nerve .
The car will go around the corner faster because you didn't throw all the weight to the front and unsettel it on the entrance of the corner.
Even more fun on a bike between 70 & 80 I get 60mpg

[811]

i agree with the above points, so i'l correct myself.. fuel economy will not only depend on how you drive, but what type of roads you drive on!

[Andyboy]

I run a 318Ti Compact (1.8 M42) and it averages 31 mpg with town and open road driving. The M42 is a more efficient unit than the M40.