2004 V70(170bhp) Fuel efficiency question

[dtjames]

To clarify, I am only surprised at the long journey economy.

[dtjames]

Originally Posted by RUTV70

A tad low perhaps...BUT around town, short journeys..in Winter.??.that's always gonna keep your mpg down....but I'd expect a little better nevertheless.
My Winter mpg has always been around the 28/29 mpg mark...with the Summer mpg increasing to 33/35 (on a good run maybe a little more).

Neil

Thanks for this. Maybe i should wait to see what happens in the warmer weather.

I am only curious since my brother's (same engine but a 2003 model) seems to get about 40mpg on a run!

Perhaps I should try a longer run without using Cruise control. Not sure what that'll prove though. I thought Cruise helped economy.

Anyone else got any ideas?

[Jim314]

Based on mpg with my V70, you are not getting the hwy mpg that you should. I think you should be getting 35 to 40 mpg. With the original tyres Michelin Energy tyres on a highway run I would get around 40 mpgUK. After changing to Michelin Primacy I get about 35 mpg on a run.

What wheels/tyres are on the car? What is the tyre pressure?

I don't know how you could test this, but could it be that the torque converter is failing to lock-up?

You could see if any codes are set.

On flat roads I think using the cruise control would raise mpg, but in hilly terrain it might lower mpg compared to driver control of speed. On congested roads driver control also might raise mpg compared to using the cruise.

Addn in editing

Just a thought . . .

To test the transmission, note the tachometer reading at constant speeds: 55 mph, 60 mph, 65 mph, 70 mph and compare this to what others find. I am sure the transmission is in 5th gear at 55 mph and above on level ground, so engine rpm/speed should be a constant. If I recall correctly, my V70 runs at 2400 rpm at 70 mph (but I'd have to check on this), for mine 2400 rpm/70 mph = 34.3, and at 80 mph I think the engine speed is 2750 rpm. 2750/80 = 34.4 rpm/mph.

If you can get your brother to determine this at one or more speeds and yours is significantly higher, this could indicate that the torque converter in yours is not in lockup.

[Jim314]

Looking at some info on gear ratios I see that the usual way to express the relationship of vehicle speed and engine speed is vehicle speed (mph) / engine speed (in 1000s rpm).

70 mph and 2400 rpm gives 70 / 2.4 = 29.2 mph/1000 rpm

80 mph and 2750 rpm gives 80 / 2.75 = 29.1 mph/1000 rpm

[dtjames]

Originally Posted by Jim314

Looking at some info on gear ratios I see that the usual way to express the relationship of vehicle speed and engine speed is vehicle speed (mph) / engine speed (in 1000s rpm).

70 mph and 2400 rpm gives 70 / 2.4 = 29.2 mph/1000 rpm

80 mph and 2750 rpm gives 80 / 2.75 = 29.1 mph/1000 rpm

Thanks for the reply.

We both have manual cars and having just been out for a run in both, rpm was identical at matching speeds.

[Jim314]

Originally Posted by dtjames

We both have manual cars and having just been out for a run in both, rpm was identical at matching speeds.

What wheels and tyres are on the two vehicles? If you don't know how long the air filter has been in, putting in a new engine air cleaner element is a standard first thing to. However it seems that modern engine controls seem to be pretty insensitive to the clogging of the filter element at least as far as mpg under part throttle is concerned.

[Jameshow]

Why should cruise control affect mpg since there are electronic accelerator control anyway.
Mine is very thirstly I have got 120miles out of £40!
7 mile or shorter cold start journeys!!!
Heavy right foot - sure the novelty will wear off!!
Yours James

[dtjames]

Originally Posted by Jim314

What wheels and tyres are on the two vehicles? If you don't know how long the air filter has been in, putting in a new engine air cleaner element is a standard first thing to. However it seems that modern engine controls seem to be pretty insensitive to the clogging of the filter element at least as far as mpg under part throttle is concerned.

Mine has 17s (fairly new P6000s all-round) and my brother's has 16s (needing changing).

My car had a 96K service last March and another service on 28th December. not sure if the air filter was changed, but having checked it last night, it looks very clean to me.

My car has had full Volvo servicing, as per schedule, since birth.

[Ricco]

Originally Posted by dtjames

Mine has 17s (fairly new P6000s all-round) and my brother's has 16s (needing changing).

My car had a 96K service last March and another service on 28th December. not sure if the air filter was changed, but having checked it last night, it looks very clean to me.

My car has had full Volvo servicing, as per schedule, since birth.

My wheels/tyres are the 16*205*55, where as yours I believe were 17*225*45 ?

[Jim314]

Originally Posted by Jameshow

Why should cruise control affect mpg since there are electronic accelerator control anyway.

Manual control of speed can be more efficient than automatic control both in hilly country or in congested traffic. Under manual control on hills the driver who drives for efficiency tends to not increase the power as agressively as the cruise control going up hills and this saves fuel. In congested traffic the driver can see ahead and feather the accelerator, leading to less energy loss in braking.