Paul67 Posted January 19, 2012 Share Posted January 19, 2012 Hi All, after fitting new plugs and air filter a couple of months ago my 1998 MB2 D14 1.4i was getting about 110 miles to £20 driving around town. But now, for some reason, the last twice I've put fuel in it's only doing about 67-70 miles to £20 before the fuel light comes on. According to an online fuel calculator I'm only getting 20 mpg. Does any have suggestions why this may be happening please? The car drives very well and I don't drive the car hard...and the only modification I have done is putting a set of 16" MG ZS hairpin alloys on it (and 205-50-16 tyres), thereby increasing the rolling radius by a mere 4.9%. Quote Link to comment Share on other sites More sharing options...
ryan.. Posted January 19, 2012 Share Posted January 19, 2012 you know fuel prices are rising so £20 now gets you less than £20 a few months ago. DONT look at how many miles you get from X amount of money. That makes no sence. You need to look at the number of litres usedThe air filter will lower the mpg a bit but you should get mid to high 30's. When was the last time the car was serviced? Thats generally the first port of call for poor mpg Quote Link to comment Share on other sites More sharing options...
Paul67 Posted January 19, 2012 Author Share Posted January 19, 2012 I hear you, but petrol has only increased by a couple of pence in the Tesco filling station I go to, so the big drop in number of miles I get per £20 has made me calculate my actual mpg. The 20 mpg was calculated using pence per litre, total spend and distance (www.fuel-economy.co.uk/calc.shtml) I use momentum 99 octane @ £1.35 per litre. And as I said, it's got new plugs and air filter. But I'm yet to change the oil, oil filter and fuel filter. Quote Link to comment Share on other sites More sharing options...
hickster Posted January 20, 2012 Share Posted January 20, 2012 4.9% is quite a big increase in size (most calculators will recomend 2.5% as a maximum deviation. 195 45 r16 is the correct size and will increase mpg due to increased torque (easier to accelerate- this more than outweighs the effect of longer legs at higher speeds you will get from the bigger tyres) and the thinner contact patch. Change them as soon as you can.Change the oil as soon as possible, this will help a lot. You could fit a Hamp oil filter that helps a little on cold startup. Sounds like you have other issues though, check the fuel system from injectors back for leaks, check your handbrake is releasing properly (two issues that can occur in this weather). Check the hairpins don't cause the inside of the tyre to bind anywhere (though from memory I think they are fine ET wise). Even aftermarket air filters should not cause the ECU to overfuel, but double check the seal on the airbox. Check you didn't split the intake hose when fitting the filter. Reset the ECU and repeat the fuel calculation, check for error codes, check exhaust/ any unsual noises or behavior. Quote Link to comment Share on other sites More sharing options...
ryan.. Posted January 20, 2012 Share Posted January 20, 2012 1. stop wasting your money on 99 octane, it makes no difference on the VTI so an MB2 will have no chance of it making any difference.2. Give it a service, always first port of call with poor mpg Quote Link to comment Share on other sites More sharing options...
Paul67 Posted January 21, 2012 Author Share Posted January 21, 2012 Massive thank you for the tips! 1"£££$££"!! The car is immaculate inside and out, (bar a tiny dent on the near side rear quarter which can't really be seen from 10 foot away - looks like a shopping trolley dent..) The bloke I bought it off in November was asking £700, but we settled on £500, as it needed 2 new CV joints and had a short MOT. Subsequently, I paid £130 for 2 new CV joints to be fitted when I bought it and it flew the MOT this month. I bought the unmarked hairpins off Gumtree for £140 with the almost new 205-50-16 tyres fitted to them (I love a bargin lol ) or else I would have gone for 45 side walls to keep the rolling radius well within the 3% industry standard... as I had read that increasing the radius would effect the MPG - but never though it would be by very much..I intend to complete the service ASAP, including oil, oil filter and fuel filter (hadn't heard of HAMP oil filters so cheers for that!). There doesn't appear to be any fuel leaks anywhere. Ive checked it over and he garage I use checked the car over for me when I bought it and got the CV joints changed, and again when I had it MOT'd. The wheels are fine too (PCD, ET and bore all spot on!) Also, 100% sure the air filter, box and intake hose is in top condition. I reset the ECU after changing the plugs and air filter when I first got the car and will again when the service is complete. There's no unusual noises or behavior and the exhaust is in perfect condition. I will however now get it checked for error codes...thanks to your suggestion! I've been reading a bit around the subject and I wondering could a faulty o2 sensor cause over fueling...and thus increased MPG??? I take it there are no MASS sensors on our cars...???Anyway, thanks again! I now have a good idea where to look to solve the problem.BTW, the 99 octane 100% definitely improves to performance of the car. With 95 octane the car drives like your average 1.3cc...but with 99 it drives like an average 1.6cc - 1.8cc...altogether far more responsive! All I can think is VTEC's must be nuts to drive! Quote Link to comment Share on other sites More sharing options...
simpo Posted January 21, 2012 Share Posted January 21, 2012 Wouldn't a dodgy O2 sensor affect the mpg? Quote Link to comment Share on other sites More sharing options...
hickster Posted January 21, 2012 Share Posted January 21, 2012 Yeah would be worth checking the o2 sensor= I think that should throw up a code. There are no MAF's on these cars ( as an ex Alfa owner I would say thank f***!).Hamp are made by Honda like NGK, the main benefit is stable oil pressure under VTEC (which won't be of much use) the filtration is no better than oem. The cold startup valve does seem to make a difference this time of year.I have found standard supermarket fuel to give fairly poor mpg in a d-series, Sainsburys being the worst I have come across (really a big difference). Not tried any of there improved octane offerings, but my guess is not as good as v-power etc. Your D14 should be not far of my D15 in terms of mpg iirc, just got 156 miles from £20 BP standard. You'll probably have the v-power club on here any moment! Quote Link to comment Share on other sites More sharing options...
Paul67 Posted January 21, 2012 Author Share Posted January 21, 2012 Cheers, thanks for the advice! Quote Link to comment Share on other sites More sharing options...
WilkesyMB6 Posted January 21, 2012 Share Posted January 21, 2012 I don't use supermarket fuel unless I have to. I don't get as good mpg as I would from any of the brands. Quote Link to comment Share on other sites More sharing options...
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