Winter diesel
 

Hi all

Apologies if this has already been asked. I seem to be getting a sharp decrease in mpg during the winter months. I have heard that fuel retailers put an additive into diesel during cold periods to reduce the likelihood of it freezing??

Does anyone know if there is any truth to this and, if so, would it cause a decline in fuel economy?

Im not sure about the additive theory, but it's more probable that it's the colder weather and darker nights, engines take longer to warm up, lights are on earlier and also its more tempting to use the car for shorter trips during this period too. Also we use the air con more to demist steamy windows in the damp weather too. My last tank was my worse since buying the car with just under 60 MPG, im sure the weather is to blame!

Tire pressure will also drop with colder weather. So there are plenty of negatives that can affect the fuel mileage. A winter blend could be one of those negatives, but teasing out how negative from the rest would be difficult.

Look at it this way, better slightly worse fuel economy than getting stuck away from home from gelled fuel.

Yes tyre pressures, tyres will expand and contract more so check pressures, I checked mine on the weekend and they had dropped a fraction, only about 5% but over time, that would keep dropping.

Well actually the tyres will expand less - due to the lower temps (and likewise will therefore contract less too) , and unless you have a leak (very possible with alloy rims - in particular old ones (won't be your problem !)) the pressure will not keep dropping ... unless of course the temperature just keeps on dropping ..... in which case we all have bigger things to worry about ! :)

Well I meant the tyres will expand and contract more as the difference in daytime/nightime temperatures will be greater in the Winter, than in the summer months when the temperature only drops a few degrees during the night.

To provide an actual answer to this question, YES, there are different formulations of diesel fuel for the winter and summer just like gasoline/petrol. A quick google search will net you far more than you care to know.

Driving a diesel, I find it takes longer to warm up, and short trips just kill mileage. Solution, take the long way to your job/store/gym, or whatever. The few extra miles/minutes on each trip won't really cost that much, and you'll enjoy driving a warm car knowing your engine will appreciate it and will return better mileage to boot. Of course, being retired allows me to do this (maybe you can't) but you should warm up the oil at least weekly to avoid problems further on. Once warm, a few extra miles per trip doesn't really cost that much!
Tenderfoot

Yes a winter blend diesel will drop mpg. The tire pressure and longer engine warm up times also. I use a winter grill block on my 2011 Golf TDI. This gets the coolant up to temperature faster on a stone cold engine.

For sure, in Canada you get more colder days than we do in North Carolina, so a grill block would be very useful. Our temps seldom drop to single digits here so a block might cause overheating after a few miles, and would be beneficial only a few times a year. I see a drop of only a couple of mpg during our coldest months (Dec-Mar), so I just add a few extra miles to my short trips during those times. The car thanks me for it, and I usually have the time. The colder intake air rewards me with "crisper" engine performance from the denser air, so I get a good feeling by doing this. I'm not sure how long we get "winter blend" fuels this far south, so you might take a bigger hit up there in winter land. Our "hit" comes during our hot summer months where the A/C runs non-stop from May to October. We enjoy visiting your country, and your beautiful scenery. Have you been to NC? Golfing? Come on down, the weather's great!

Tenderfoot