1.4tsi cold weather MPG

[POIDH]

Usually on a run my Leon estate with 1.4tsi will easily do 50mpg, often more.
However, the last couple of subzero days it's struggled to get over 35-40mpg. That's 20-25% less.

I'm used to a drop in mpg, but this seems a lot. Is this usual for this engine?


(It's currently on a tank of Shell, it's missing the engine undertray which doesn't help things, and as example I've just done 60-70mph for 70miles on motorway in central Scotland at -7 air and compared with a couple of weeks back same journey in 5*c).

[somouk]

I find my 1.5 TSI is about the same and seeing the same drop in fuel usage considering the temp.

[Malcs87]

If it helps, I am having the same issue with my Leon estate. Same engine. I usually 50mpg on my commute (motorway & A roads) but down to 45mpg of late on my commute. I've put it down to having the air con/heater on.

[Tony1963]

C’mon lads!

Your engine, not just the coolant, takes much longer to warm up and reach its efficient temperature. That’s the major contributor to poor mpg.

Also, check your tyres, they could be a few psi down in the cold.

[POIDH]

Tony1963 said:

Your engine, not just the coolant, takes much longer to warm up and reach its efficient temperature. That’s the major contributor to poor mpg.

It does, but only a few minutes on yesterdays motorway run over an hour and a half. And even when 'hot' (resolutely sits at 90*c) at the end of the motorway it was still only doing late 30's mpg.

Tony1963 said:

Also, check your tyres, they could be a few psi down in the cold.

Yep, checked yesterday and topped up a couple of psi to middle of the recommended range. Certainly not low.

[Sheepshanks]

POIDH said:

And even when 'hot' (resolutely sits at 90*c) at the end of the motorway it was still only doing late 30's mpg.

There's a reason it sits resolutely at 90C - it's not diplaying the actual water temp! It's driven by the ECU and it's basically just saying "OK".

I don't know if the petrol's can do this, but my wife's diesel VW can show the oil temp in the multi-fuction display.

Her car will blow warm air astonishingly quickly (no electic booster heater in the latest ones either) and it will show 90C at 3-4 miles. However select the oil temp and it's still blank - it's starts at 50C and you're well into the teens of miles before that hits 90C. MPG is quite a bit lower now in her car too - did a gentle 60 mile round trip early this morning that would normally be nudging 50MPG and it only just broke 40, and I know the trip MPG reading is a good 5% optimistic.

[POIDH]

Ah, that's interesting. I'll see if I can see oil temp, not coolant temp somehow.

[Tony1963]

A few pointers here:

https://www.holtsauto.com/redex/news/how-cold-temp...

Note the point about increased drag in cold air. So driving at 70mph on a motorway for an hour could suffer noticeably from that.

[2 sMoKiN bArReLs]

Off topic...but similar.

I used to drive Nottingham>>>>St Albans>>>>Nottingham three weekends a month in my VW Golf R32.

I often managed 28 mpg, but noticed if it was hammering down with rain it dropped to about 22 mpg.

The only thing I could think of was the car engaged 4 wheel drive in heavy rain?

Edited by 2 sMoKiN bArReLs on Thursday 15th December 17:40

[Sheepshanks]

I drove the Tiguan down South a couple of weeks ago and the entire journey was in the most appalling rain - several times on the M40 it was like someone was standing on the bonnet with a fire hose. Did most of the journey at 60 and very few people passed me.

What I noticed was the car was constantly changing down to 6th when normally it hangs on to 7th too long. I assume that was just from the extra resistance of the surface water. Despite the speed, and that it was a pretty steady journey with no hold-ups, the car only did 40MPG on the trip - would usually be near 50, driving at 75ish.


Did a 7 mile round trip this morning to drop granddaughter for her school bus - drove straight off, no de-ice needed - was showing 22MPG when I got back.

Edited by Sheepshanks on Thursday 15th December 17:43

[M11rph]

2 sMoKiN bArReLs said:

Off topic...but similar.

I used to drive Nottingham>>>>St Albans>>>>Nottingham three weekends a month in my VW Golf R32.

I often managed 28 mpg, but noticed if it was hammering down with rain it dropped to about 22 mpg.

The only thing I could think of was the car engaged 4 wheel drive in heavy rain?

Edited by 2 sMoKiN bArReLs on Thursday 15th December 17:40

There's more drag on the wheels when running on a saturated surface. That plume of spray behind you is water that your car has had to lift from the surface. Seems trivial, until you start looking at how much water your vehicle is displacing.

There's an additional aerodynamic penalty for having a wet car, although nothing like one wearing a "frost hat". Wipers when used add drag too.

Lastly there's a small penalty as most modern cars periodically apply some braking in the wet to clear the discs.

Edited by M11rph on Thursday 15th December 18:30

[2 sMoKiN bArReLs]

M11rph said:

2 sMoKiN bArReLs said:

Off topic...but similar.

I used to drive Nottingham>>>>St Albans>>>>Nottingham three weekends a month in my VW Golf R32.

I often managed 28 mpg, but noticed if it was hammering down with rain it dropped to about 22 mpg.

The only thing I could think of was the car engaged 4 wheel drive in heavy rain?

Edited by 2 sMoKiN bArReLs on Thursday 15th December 17:40

There's more drag on the wheels when running on a saturated surface. That plume of spray behind you is water that your car has had to lift from the surface. Seems trivial, until you start looking at how much water your vehicle is displacing.

There's an additional aerodynamic penalty for having a wet car, although nothing like one wearing a "frost hat". Wipers when used add drag too.

Lastly there's a small penalty as most modern cars periodically apply some braking in the wet to clear the discs.

Edited by M11rph on Thursday 15th December 18:30

Makes sense. Mind, I've done that journey for 20 years & in no other vehicle was it so pronounced