My daily commute to work isn't very long. About 4 miles i'ld say so my mpg isn't great at the best of times but I checked it last week and usually I get about 25-27 mpg driving steady from my 2.4 but now I'm only getting about 21? At first I suspected tyre pressures were to blame and sure anough they were 4 psi down on each corner so I put some more wind in and reset and checked again next day and pushed it up to 22.5 mpg better but still off the normal 25-27 mark? It's also down on motorways too as a trip to the NEC proved when I could only get 31.5 at 60 mph - down from 37-42 that I can usually get?

Any ideas? It still runs ok but the only thing I have done in the last 3 weeks is change my oil from 0w 30 to 5w 40. Could the marginally thicker oil affect fuel consumption? Or should I be looking somewhere else?

if its the only thing you changed in a reletively short timespan id be putting 0w30 back in bud!

but to answer your question... oil viscosity does effect MPG

Lol now that would be costly

LMAO WD40 FTW!!:slayer:

Yeah that'll do? ...... Should get 70mpg on that? ...... If it makes it that far Lololol plus it'll smell good too?

Dont forget the weathers turning pretty cold around now, especially on a 4 mile trip i bet u barely get up on the gauge.
Is yours 2.4 ? Ow30 sounds a bit thin anyway but range does affect mpg but id guess 1-2mpg per range, so a change from 0w30 to 20w60 might give that sort of drop.
Try tripping on a warm day and again on a frosty day.

sussexa said:

Try tripping on a warm day and again on a frosty day.

Click to expand...

I'll be waiting for a while then ........ I also thought 0w was a bit thin hence why I moved to 5w. I can't believe a 5 mpg fuel drop can happen from just a slightly thicker oil though? The days are a lot colder at the moment and yes it only just gets warm before I switch it off but I gave it a good run at the weekend and it was still down 5 mpg?

i noticed this last week, in july i drove to exeter and i was averaging 58-63 mpg in my jtd, i went again the weekend just passed and it was -1 there and pretty damn cold in essex ( i left at 5am) and i could only manage 52mpg, on the return journey i managed 48mpg but was quite a bit colder

Im assuming for jtd the refiners have switched to winter fuel mix, less energy in it and mpg would drop in same weather just on winter mix(additives to prevent waxing)
Im usually dropping to low 40's in winter and high 40's in summer , short trips also usually 1/2 way there before i get half way on temp gauge
Due to being off throttle most of the way as down hill to work.warms up alot quicker on way home as uphill and on throttle.

[ame]http://en.wikipedia.org/wiki/Winter_diesel_fuel[/ame]
looks like november till march(biodiesel)?
Designation CFPP value time frame Cloud Point Summer Fuel -5 °C 16.03. - 15.11. 3 °C Winter Fuel -15 °C 16.11. - 15.03. -5 °C

http://www.mabanaft.com/Mabanaft/images/pdf/prodspec-Diesel.pdf
Unless otherwise advised the following seasonal dates apply: Summer: 16/03 - 15/10 (terminals),
Summer: 16/03 - 15/11 (retail sites), Winter: 16/11 - 15/03

i had assumed bsfc was fuel related, but looks more like engine design than fuel.
[ame]http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption[/ame]

gadgemyster said:

the only thing I have done in the last 3 weeks is change my oil from 0w 30 to 5w 40.

Click to expand...

Why did you do that?

Well after a year of using the Mobil 0w I found the engine to be a little noisier than I remembered also the oil consumption was the worse than the year before leading me to think that perhaps the oil was too thin of my engine? The handbook recommends 10w 40 so I figured 5w 40 wou
D be a better choice? ....... It's now a lot quiter and I haven't had to tip it up yet? ........ Plus I like to change my oil before the winter time