mx5cartalk.com

Hey boys and girls,

I recently bought a 2002 NB and i feel that i am not getting as many KMS per tank as i should.

At the moment i am getting an average of 360 kms per tank of city/ hills driving.

Does anyone else do similar driving and find they are getting more kms?

What could be some of the issues? I have thought it may be an O2 senor that isnt working correctly, but am open to other suggestions.

My NA6 (1989) seemed to get more kms per tank of fuel and that was driving the exact same route and i am now with my NB

Much appreciated everyone

Hmmmm. That does look a little on the low side for a normal NB (my SP with spirited driving will only give me about 300-340kms per tank). I would have thought a normal NB would get close to 450-500kms from it's 48 litre tank - depending on driving style and type.

What fuel are you using?

My 2002 NB8C gets about 8L/100km if I don't drive the wheels off it. I don't know how many KMs that is per complete tank but I usually get 400 before I fill up with about 35-40L of 98. 360km definitely sounds on the low side if that's a full tank.

Sorry to throw back more questions, but it does affect the answer you'll get.

How many litres do you usually buy when you fill up? For example, a 29L fill would mean 8.0L/100km and you would be pretty happy with that. But a 35L fill would mean 9.7L/100km which is on the high side. (assuming "360km per tank" in both calculations)

What type of fuel do you buy (91RON, E10, 95RON, 98RON)? Higher octane fuel generally gives slightly lower fuel consumption, although it's debatable whether or not the extra cost justifies it.

Is your NB8B modified? The tune can influence fuel consumption ... either increase or decrease depending on what's been done.

What size tyres are fitted on your NB8B? Tyre size affects the rolling circumference, which changes the calibration of the odometer. The difference is subtle however, if the tyre size is in legal limits.

Missy

Sounds very low economy to me! I will stand corrected but the NB tank is 48 litres and the NA is 45 litres

My NB averages 7.5 litres/100km so assume to go right down low that's 600km on a tank with 'average' driving but much more on a trip. My '89 NA has a high performance engine and i do give it a bit of 'stick' up to around 6000-6500rpm quite often [onto the freeway of course!] and it also averages around 7.5 litres/100. I filled it the other day and had done 454km and took 36.2 litres - that tank averaged 7.97L/100km

If you PM me with your email I will forward 'excel' spreadsheets for bothe NA & NB since I have had them .. I can usually call into my local SHELL and calculate within 1 litre of how much each will take

I run 'SHELL V-SUPER' 98 Octane 99% of the time, if not available then BP 'Ultimate'

zero00 wrote:............My NB averages 7.5 litres/100km ........... My '89 NA .... averages around 7.5 litres/100.....
I do give it a bit of 'stick' up to around 6000-6500rpm

Trying not to sound harsh but you're kidding us aren't you either that or you knock it out of gear going down hill and creep up hill. Those figure are obtainable for country runs but not stop start city runs. As for giving it stick sounds like anything over 4,000rpm is almost a no go zone. Hell, this car was built to be enjoyed, not to try and win economy trials.

Missy, 3 years ownership of a stock standard NB8C from new in daily city driving averaged 9.5 litres per 100 kilometres. Put it on the track and it used 27 litres per 100 kilometres.

My NC used 0.5 litres less per 100 kilometres before the Deckspeed flash tune, now it’s a litre less than the NB.

Only way to accurately figure out fuel economy is to keep a log of Km travelled / Lts used.

Missy wrote:Hey boys and girls,

I recently bought a 2002 NB and i feel that i am not getting as many KMS per tank as i should.

What could be some of the issues? I have thought it may be an O2 senor that isnt working correctly, but am open to other suggestions.

Aircleaner clogged. Dragging brakes.

Thanks everyone for all your replies... appreciate it!!

I fill my tank from close to empty all the way to full with 95ron from BP.

It takes me 30 mins to get to work in Adelaide. I do 8 - 9 mins of flowing hills driving (no stop lights) then its SA peak hour - which really isnt too bad.

I have been keeping track on the kms on my trip metres... both close to 360 - 365 each time.

My NB is stock standard. The only that it has different on it is 17inch rims that the previous owner put on them. My tire pressure is 36 all round.

I will admit that i dont baby my car... but i dont thrash the guts out of it.... kinda hard to in peak hour.

Charlie Brown wrote:Missy, 3 years ownership of a stock standard NB8C from new in daily city driving averaged 9.5 litres per 100 kilometres. Put it on the track and it used 27 litres per 100 kilometres.

Indeed, my NB8B rarely gets below 10L/100km, that's driving in Sydney traffic. Funnily enough going for a blast through the royal national park, sitting above 4000RPM and accelerating hard out of corners uses less fuel

Traffic makes a big difference. My diesel Peugeot gets around 6.2L/100km in Sydney traffic, on our honeymoon in Tasmania's 'traffic' it averaged 4.5L/100km...

Missy wrote:i am getting an average of 360 kms per tank of city/ hills driving.

Depends on how you & where you drive, but 360 kms / tank is at the lower end. Then again you city drive in peak hour (ADEL), so if you also sink the slipper a bit then it's probably about average.

zero00 wrote:I will stand corrected but the NB tank is 48 litres and the NA is 45 litres.

NA6 tank is 45, but NA8 tank is 48.

Missy wrote:I fill my tank from close to empty all the way to full with 95ron from BP.

How many litres of fuel is that? Some people's idea of "close to empty" might be when the gauge reaches a quarter. You really do need to record the volume of fuel added in addition to the trip meter reading. Divide one by the other and "Bob's your uncle", you have fuel consumption in L/100km.

My NB is stock standard. The only that it has different on it is 17inch rims that the previous owner put on them. My tire pressure is 36 all round.

What size tyres are fitted to those 17" wheels?

My version of empty is when the needle is on E... i fill the tank to full... when the pump clicks and you cant fit any more fuel in....

The tires are 205/40/17 all round...

I know how to work out my fuel consumption, i more so wanted to know what other 2002 NB drivers were getting out of their tanks with close to similar driving conditions.

I was also after some suggestions of what i could look at as the problem - eg my O2 sensor.... and someone else suggested it may be my Cam Angle Sensor that may be the issue

thanks again everyone, very helpful!

Missy wrote:My version of empty is when the needle is on E... i fill the tank to full... when the pump clicks and you cant fit any more fuel in....

When the needle is on E, you still have about 7-8 litres in the tank, so let's assume you're doing 40L fills. That's 11L/100km which is definitely high for urban driving in an NB8B.

Is your NB an auto? Auto in stop-start traffic might normally use a bit more fuel than a manual.

The tires are 205/40/17 all round...

OK, that's not the reason then. Those tyres are only 5mm larger in diameter than the stock 205/45R16 tyres and not likely to have a noticeable affect on fuel consumption.