MPG help please

[Anonymous]

Hi All,
I would appreciate some information/advice on fuel MPG return figures. I’m the proud owner of a 62 plate 156 petrol model, which appears to be returning some very low MPG figures. City driving, driving responsibly, it struggles to return above 33mpg, driving progressively city/motorway around 30/31mpg. I’ve even took it on a 200 mile round trip (Glasgow-Oban), with a combination of urban, motorway and rural driving. Can anyone give me some figures on what I should be getting and suggestions on what the issue may be (heavy foot not being one of them) ;-)

Paul

 

[Anonymous]

Hi Paul

I also have a 156 Petrol 62 plate, so I'll let you know what I get.

I do a 250 mile round trip once a month or so using mainly motorways (M45, M1, M25) which gets me around 40-42 mpg for the trip. That's with a lot of going 85 or so.

General use I seem to get around 35-37mpg, for which I'm not exactly driving frugally (is that even a word?).

I have noticed that using engine braking makes a big difference. Are you doing that? As far as I'm aware the RCZ employs fuel shut off when the engine is being turned by the wheels. That would explain why the mpg counter goes to 999.9 when coasting in gear.

Not sure what RPM it starts refuelling though.

 

[Anonymous]

Thanks for that information and yes frugally is a word ;-) . I reckon that I must be down between 5 and 10 miles per gallon, each gallon. I’ve tried driving normally and also extremely sensibly, aware of gear changes and such like. I do tend to engine brake rather than coast, years of riding a bike, never was a fan of freewheeling, Would engine braking make such a huge different to fuel economy. I’m just gobsmacked to read everywhere that people are quoting mid to high forties for mpg.

 

[RCZ1]

Mines a 2010 156 and I average 40-42mpg. My journeys are daily commutes 12 mike round trip plus country road drives 3 times a week - about 90 ish miles each time. On a country road run I routinely get 45+mpg. Only last week I got 49mpg on one of those journeys.

When I went to Shrewsbury for the Detailing Day last April, a 325 mile round trip, I got 49.7mpg. Believe me I wasn't taking it steady as it was the first time I'd had the opportunity to take Pearl on the motorway and I was doing 2nd stage spoiler speeds at some points but certainly never lower than 80mph.

I tend to accelerate at a steady pace rather than heavily and I do engine break most of the time. I don't tend to rev the engine. I'm very happy with my mpg and it's always been the same.

Just one thought, are you reading computer 1 or 2? Computer 2 gets "stuck" when you've done 6000 miles. Reset it every 6k miles and you'll get a true reading.

 

[Anonymous]

Also, and I'm sure you'll attest this RCZ1, the handbook states that the MPG doesn't become stable until around 3k miles.

 

[Anonymous]

When I passed my advanced driving test in 2005, my police examiner told me to use my brakes to slow down, not my gears, he said that brake pads were cheaper than gearboxes!

 

[Anonymous]

I was told that as well, and did so for 3 years However, from a fuel perspective you get a higher MPG by using engine braking correctly!

 

[Anonymous]

I did see that 3k thing in the manual, not reached that marker yet but should fairly soon. I’m also reading both computer 1 and 2, I tend to reset every trip computer and counter when I refuel, just to give me an estimate of range and mpg. Should I not zero them and just leave them running. I wasn’t sure if my figures were something I should flag up to the dealer, just didn’t want him saying oh combination of city driving and heavy foot because that is not always the case and the figures struggle to get past 30mpg, its becoming a pretty but expensive runabout

 

[RCZ1]

I only reset computer 1 when I fill up. I leave computer 2 until it reaches 6000 miles, them I reset it. Computer 2 gives you a summary of your mpg and average speed over that 6k miles. I find it useful and it more or less matches my Road Trip app that I use to log costs, economy, etc on my RCZ.

 

[Anonymous]

Like you, Paul42u, I think this is lower than I would expect. I get 30mpg from mine which is a 62 plate Sport 200.

My other car is a low miles 12yr old Honda HR-V which I also get 30mpg out of. The same went for my previous Astra's and Cavaliers and the Ford's before that over the previous, what, 30 years...I seem to be fated to only achieve around 30mpg! My driving style now is the same as with all those previous cars but I would've expected to get better mpg as technology moves on.

My RCZ has a little over 3000 miles on her now and for the last 1500 miles I've been resetting my trip computers the same way as RCZ1. My driving is a 50/50 mix of urban and dual carriageway 99% of the time and my driving style is a mix of gentle driving (especially in traffic) and heavy acceleration when the road conditions permit. I'm averaging 30mpg both now and since new, there's no sign of it settling into any other pattern even now that I've done just over 3000 miles. On the odd occasion I do a longer trip of a couple of hundred miles on motorway I see low 40s but to be fair I do tend to be heavy footed when overtaking.

On the display I see mid-teens when accelerating hard which is understandable, but being acceleration this is necessarily only for short periods. Most of the time when I glance down during long stretches of normal driving I'm getting 40s/50s and more so I don't know why my overall mpg is so low. A few brief seconds of poor mpg under acceleration -vs- longer periods of 40s/50s should surely skew more towards the higher end?

At first I thought it might simply be poor calculation software but judging by how many miles I can do before the low fuel warning comes on it does bear out at about the 30mpg the computer is reporting.

I'm going to give it to 4000 miles and if it doesn't improve I'll pop it to the dealer for a diagnostic and I would suggest you do something similar.

 

[Anonymous]

Thanks Guys for all the replies,
Steve, I think our driving styles must be fairly similar, I tend to notice mid teens to low 20’s on acceleration and anywhere from mid forties to high 80’s on regular driving, hence the surprise when the calculation comes back at 30mpg. I was very disappointed to fill her up and see the trip range state 325 miles. Not since my land rover days have I experienced less than 100 miles for 20 bucks of fuel. I also think I will be going for a diagnostic test at the dealer at 4000 miles.