Faster=Better MPG

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jc denton

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Who thinks that a large engined car is more fuel efficient at higher speeds??

I'm not talking about diesels here. One a long run at a constent speed around 70-120mph, larger engined petrols seem to do better mpg than smaller ones. Or am I just imagining things?
 
A 1.0 engine will be revving its guts out at 85mph but a 1.4 will happily sit at that speed and use less fuel than a 3.0 V6.

Bear in mind that bigger engines tend to come in bigger cars, which means they have more weight to pull. Plus the engines obviously weight more.

Providing an engine sits at it's peak bgp point at the set speed it is running efficiently. For most cars this is around 3000 rpm.
 
The reason I posted this thread is because I was using a 1.8L audi for a 60mile run on an A road averaging 100mph & my 2.5L V6 galant seems to be using less fuel doing the same.
 
It is an interesting concept but I think we really need more real world data to work on. The extra Urban MPG figures might be the way to go on this but I think we are talking about much higher than cruising speeds here.

I recall on TopGear they sent an M3 and Prius round the track and the M3 had better fuel economy as the Prius was going flat out and the M3 matched it's speed without breaking a sweat.

I always lament that on a motorway at 70mph I'm getting about 35-40mpg and smaller engined cars are probably getting nearer 70mpg. Perhaps the gap is not as wide as I think.
 
Yugguy said:
That's probably because they're geared differently so aren't revving as high for a given speed.
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Agree.

My MPG goes up from about 17 to about 30 on motorway runs. This has nothing to do with the size of the engine, just how it sits with the revs. It will sit at about 2700rmp doing 70, where as my mazda would sit at 70 doing about 3800rmp and some how, use more fule than my evo! Even tho they are both 2L.

My best out of my Evo is 32mpg and my verry best (night driving, no 50 zones, no slowing down Carlisle to M5, and no traffic jam's) was 34mph
 
bigbadjoe said:
Agree.
My best out of my Evo is 32mpg and my verry best (night driving, no 50 zones, no slowing down Carlisle to M5, and no traffic jam's) was 34mph
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34mph? :blink: now that is impressive considering the monster you drive BBJ! :amazed:
 
bigbadjoe said:
:blink: sorry, i forgot to rite 34mpg was the best I got out of the Mazda!! My bad.

No, 32 is the best out of the Evo
34 is the best out of my 323 mazda
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Ah ha! that's still pretty good, as the best I have had out of the Beast so far is 27.1mpg and that was driving like Miss Daisy :lol:
 
T9 man said:
I have a feeling you were over the moon with that Hdi ;)
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Not disappointed for what is a heavy car and driven at speed. I was not looking especially for economy but seized the opportunity to make a point to all those who tell me my big hefty car must cost a fortune to run. Dad - are you LISTENING :) !!!
 
T9 - You do know that the right pedal on the floor of your car is pressure sensative and it doesn't always need to be glued to the floor! 27.1mpg!! at very best :amazed:

Have you fitted a 6 speed box in there and just forgot? You need to get it into top gear mate!! :)
 
bigbadjoe said:
T9 - You do know that the right pedal on the floor of your car is pressure sensative and it doesn't always need to be glued to the floor! 27.1mpg!! at very best :amazed:

Have you fitted a 6 speed box in there and just forgot? You need to get it into top gear mate!! :)
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:lol: Thanks for the pearls of wisdom BBJ :bigsmile:
 
Yes, I've find that high speeds on the open road tend to favour a large / more powerful engine.

I get the same highway economy from a twin turbo V6 as I do from a 1.8 Corolla that I hired - the athe TTV6 was a lot more fun!

High revs, steep hills and having to thrash the Corolla when overtaking trucks hurt its consumption badly.
 
I think there should be an additional mpg figure for new cars: Highway, Urban & Race.

Thrashing my galant makes drink like mad. But then, just keeping up with a 2.0L mazda that is being thrashed (driven as fast as the driver dares anyway) & I seem to be getting better mpg...


I've come to the conclusion that if you want an economical car, don't just go for which ever has the best mpg figures, decide which is most suited to your driving style.
 
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With the average annual fuel cost of £2000 and buying an economical car only reducing this to £1500 I doubt buying for MPG makes much sense. Just get the car you want and have fun with it.

That's what I did! Ok it costs a little more to run than our A3 but I get 50% more enjoyment from it.
 
I ask'd my sister who has a 1.4L diesel yaris, last monday to fill it up & start the clock. I filled my tank the same day & I only just ran out today after 300 miles, she ran out to day as well after 480 miles.

So the way I see it; I spent £800 buying my galant because its good looking & she spent over £6000 on her yaris c'os its cheap. But she's only saving about £30 per weak???!!! & I don't have to hang my head in shame every time I go anywhere.
 
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30 quid a week is a big difference tbh. Bigger engines doesn't always mean better MPG. There is driver style, road conditions, type of road and so many other factors to consider a comparison.
For example did you both drive the exact same roads throughout the whole tank? And also at the same time in the same traffic etc?
 
I've actually been thrashing mine just a little bit & she always drives very carfully.

It is funny that we both ran out on the same day isn't it?


Question: Would You suffer a yaris to save £30 week?? ... didn't think so.
 
£30 a week is a lot of money dude, £120 a month, or £1440 a year, if it was a second car and used as a daily driver then yes I would, I had a Yaris 1.4 diesel as a courticy car a long time ago (neighbour reversed into me) and I thought it was a good little car, well built and economical.
 
Then I guess your not as big a petrol head as I am jarrus:p

Still tho, a 1.4 diesel & a 2.5 v6 are at opposite ends of the scale when it comes to economy & there is only about £30 per week in it.

Like wayne said: Get the car you want & just enjoy it!:D:D
 
I dont think you've understood what ive said, I would only have one if I had another car as a play thing, I wouldn't have one as my only car definately not but I dot think you give them enough credit though cause they are brilliant at doing what they re ment to do, get you from a to b.
 
Clearly smaller is only better if your going to correlate your driving style to the capabilities of the engine. My dad has a Freelander 2 - 2.2 TD4, and I have a Range Rover Sport 3.6 TDV8.. I can get better MPG in the 2.7 tonne sport than he can get in the 1.6 tonne Freelander when going for a 'blast' down the lanes... presumably because Dad is driving the Freelander like a complete hoon, and the TDV8 isn't breaking a sweat to keep pace.
 
RobBentley said:
Clearly smaller is only better if your going to correlate your driving style to the capabilities of the engine. My dad has a Freelander 2 - 2.2 TD4, and I have a Range Rover Sport 3.6 TDV8.. I can get better MPG in the 2.7 tonne sport than he can get in the 1.6 tonne Freelander when going for a 'blast' down the lanes... presumably because Dad is driving the Freelander like a complete hoon, and the TDV8 isn't breaking a sweat to keep pace.
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That'll be exactly why.
 
They did that on top get with a Prius and an m3 the m3 did better mpg because it wasn't breaking a sweat and the Prius was being ragged
 
Thats why I want another prelude.


A few snippets from the mpg page, I've updated them accordingly...


Avoid idling the engine for long periods of time - turn it off at railway crossings etc... Wrong! Rev the engine repeatedly when ever you stop, so you can listen to that wicked sounding exaust note.

Put some injector cleaning like redex in - it really does help keep things at peak efficiency and in my car added 2 mpg! You don't need any of that fancy s***t, whisky does a better job & smells nicer.

Fuel magnets did not work for me I wouldn't bother with them!!! I think they only have an effect over several years.

Don't be lazy. Walk to the corner shop - it's only 3 minutes away. Wrong! whats the problem with driving 40 odd miles on some nice empty A roads & going to the corner shop in the next town?

& make sure you have the AC on full, all the way & heat the empty seats if it gets cold!
 
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Im amazed there is so much surprise about mpg

Simplez really
I will leave out the obvious - weight hybrid etc

What most people forget is that the new fuel efficient engines ( even the gas guzzling ones) are sooooooo nuch better than earlier cars , and thats not because they are worn out.
Same apllies to a proper map with a truly decent ECU you will get more power and better mpg.


Smaller engines are obviously more economical but only as long as they are driven in the right rev range and are not being over stretched
Each engine has a range where it is relatively fuel efficient.

As far as running other things - awd , air con etc makes a difference but far more so on a small engine.


I never get over 20mpg but I think thats good for nearly 600bhp , AWD, and in a car that weighs as much as a house
But because it has a seriously good map I get only a few less mpg than a std auto car with half the power unless of course I use a lead right foot.... which I am prone to do - if youve got it use it.

Thats why I have a late civic coupe as my main driver.
 
Redex is not bad stuff in my opinion but shouldn't be necessary if you use decent fuel. BG44K and BK244 are probably the finest cleansing additives on the market with Forte's products a close second.
 
Driving a 2.4 iVTEC Honda Accord with a 65 ltr fuel tank. I always fill with super. Best tank I've had was 90% motorway driving cruise control at 70mph or there about. Refilled after about 430 miles, probably could have gone to 450 though. The paperwork for the car says the best possible tank I could expect to get is just over 400, so I was very chuffed with that indeed. Although, we all know that manufacturers (at least Japanese manufactures) tend to be conservative with their paper based claims.

For sure, high speed cruising, big engines are better. I'll sit at 70mph at little above 2000rpm in a car that redlines at 7000rpm. Whereas if I was driving a little poky car I might be high up the revs to get 70mph. Meaning I'd be burning more fuel.

Some big cars are marketed as great motorway cars. Mine is one of these for sure, the diesel version even more so. I believe you'll get well over 600 miles from a tank with the Diesel Accord. That's their newer DTEC range by the way. With the 7th generation of accord, Honda ventured into making their own Diesel engines for the first time instead of fitting Isuzu Diesel engines. They could be a diesel to watch I reckon. But enough about Diesel.

100% round town driving, my worst tank, I got 270 miles before the fuel light came on. I reckon if I ragged it and really enjoyed it's potential, I could get as little 200 before needing a refill :lol:. But that's never gonna happen really.
 
Wow, my 306 has a postively massive fuel tank for it's size..... (60 litres, 62 if it's scraping the barrel) most I've had out of a tank was 650 miles driving from my home near Cannock to Solihull for 11 days, I think it worked out to about 45 mpg, I was doing 90 most of the way there and back. That was when I had the 1.9litre in there with a mild tune, I reckon it was running about 110 hp and 160 lbft
 
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