Realistic max MPG for a 1390cc Volkswagen Polo

[Rembrant]

Originally Posted by ecomodded

Also I use a cheap diesel tuning box , for fast throttle response and early power.

What is your cheap diesel tuning box?

[Bataleon]

Originally Posted by awcook

3300 RPM @ 60 is crazy, but I drive an auto which is totally different. At 3300 RPM I'm traveling at around 85 MPH. At 2500 RPM I'm at ~75 and 1900 RPM for 60 MPH. Your car should be getting better MPG than 36-40 on all highway trips though. My car does ~44 MPG on highway trips without even trying that hard (70-80 MPH, always running, no neutral coasting). Maybe you should do P&G with neutral coasting from 65-55 or something. I'm not sure how far your car will coast while doing that, but it's bound to help you.

Luckily my VW isn't quite that high: 3000 RPM @ 60 MPH.

What size engine is your automatic? ~44 MPG without trying is very impressive, especially for an auto.

I've tried P&G but my car slows down very quickly, even on a level road. I guess it's time to start looking at some minor aero mods.

[awcook]

My engine size is 1.8L, so probably more powerful than your VW. Getting high MPGs on the highway is probably much easier in an automatic than a manual if you don't drive like a maniac and do some minor DWL. P&G isn't worth it at higher speeds, since your car slows down much faster at 60 than it does at 40. I know my car can coast from 45-35 for about 1/2 a mile (did it on a backroad, no traffic to get mad at me).

[renault_megane_dci]

My wife gets 36 in traffic with her manual 1.4 16V gas Audi A2 from 2001 (75hp).
Average speed is anywhere between 30 mph to 60 mph.
She is not an hypermiller but a short shifter.

The weight is pretty much the same and the Cd is obviously in favor of the A2.

Conclusion is : aeromod your car

[RunningStrong]

How long does the coolant take to warm up? What are ambient temperatures like at the moment?

The VW PD diesel engines are very slow to warm up, so the grill block provides thermal benefits and not just aero. I'd check the thermostat too if you're not reading dead-centre on the coolant temp, VW thermostats are easy enough to replace but known to go.

Have you got a full undertray under the engine bay? If not you may be able to get one off a Bluemotion model and there could be minimal work required to get it to fit.

[renault_megane_dci]

Weren't we discussing a gas engine ?

[Bataleon]

Originally Posted by renault_megane_dci

My wife gets 36 in traffic with her manual 1.4 16V gas Audi A2 from 2001 (75hp).
Average speed is anywhere between 30 mph to 60 mph.
She is not an hypermiller but a short shifter.

The weight is pretty much the same and the Cd is obviously in favor of the A2.

Conclusion is : aeromod your car

I reckon you're spot on. I recently drove 80 miles in a Ford Figo 1.4l (identical weight as my VW Polo) and managed 39.2 MPG US whereas I usually get 36 MPG US on the same route with my Polo.

The Polo's Cd is 0.32 so there's definite room for improvement. I noticed the Ford Figo coasted in neutral a lot better too.

Originally Posted by RunningStrong

How long does the coolant take to warm up? What are ambient temperatures like at the moment?

The VW PD diesel engines are very slow to warm up, so the grill block provides thermal benefits and not just aero. I'd check the thermostat too if you're not reading dead-centre on the coolant temp, VW thermostats are easy enough to replace but known to go.

Have you got a full undertray under the engine bay? If not you may be able to get one off a Bluemotion model and there could be minimal work required to get it to fit.

From cold start in the morning (20°C ambient) the engine takes around 3-4 minutes to warm up completely (needle sitting on dead-centre). After which the engine drops from ~1100 RPM idle to ~800 RPM idle.

I don't have any aero mods installed at the moment. A Bluemotion underbelly sounds like a great option. Thanks for the idea.

Originally Posted by renault_megane_dci

Weren't we discussing a gas engine ?

Yep 1.4l gas/petrol engine.

[renault_megane_dci]

How good are you at P&G ?
After all, it's just a matter of finding the sweet spot speed wise ...

[Bataleon]

Originally Posted by renault_megane_dci

How good are you at P&G ?
After all, it's just a matter of finding the sweet spot speed wise ...

I've started using P&G a lot when driving in town but at speeds above 50 MPH my car slows down very quickly.

Town runs are usually short most of the time (3-5 miles each way) so the engine is far from reaching its optimum efficiency.

What speeds do you P&G between? And do you use the technique only when on flat ground?

[renault_megane_dci]

I am not too good as seen in my fuel logs.

In the A2, I feel more comfortable from 30 to 50 mph, anything in 5th really.

The Megane on the other hand is better above 60 mph but also can be quite good in town at 30mph where it seems to be gliding for ever.

Check your brake drag.
The Megane from 2003 is apparently really good in this respect, this is what is said inside Renault at least.