Diesel v Petrol.

[lordyoung1980]

Sorry if this is the wrong section or a FAQ, but i figured you guys might be the ones to know. In 2002 i bought my first Diesel daily,this was a result of my mini getting smashed up by some joy riders and the fact that my Land Rover 2.25 petrol 90 had horrific fuel consumption. It was a 1995 pug 306 turbo diesel and i loved it. In 1 year i did 50000 miles with only servicing and a set of rear brake shoes. It soldiered on till 2005 i had a new job and treated myself to a 306 2.0 HDi, again sterling service it provided until 2008 when it broke through no fault of its own. By this time i didnt need to do so many miles and bought a Petrol 1.6 Audi A3 sport. After 6 months of constant faults and breakdowns i bought a Renault sport 172 2.0. I loved that car,it covered so many bases. It was fast, and when i wanted it to be frugal too 51mpg was a record. But alas my daughter was born and we needed a bigger car, having no money i traded in for an Audi A4 avant, its a 1.8 20v and i feel it drinks too much fuel. Today i traveled from Corby to Stanstead airport and back, before i left it had a quater of a tank so put £20 in that took it to just under half . The fuel light came on near Thrapston and just got me home,by my guess/judgement call it what you will its cost me £50 to do that journey. I know this is a bit long winded but theres a point, or rather a question. Whats better Petrol or Diesel? Now i know i could go on What cars website and trawl through MPG figures and the like, but what i want to know is,whats the real world figures? what are you guys finding at the minute running both fuels Diesel costs more against petrol but its a more economical engine Etc. I average 10 to 11 k a year in mileage so what would you think is better. I'm looking to change my car soon and wondered what your thoughts and recomendations are. I need to look at cars that are similar in size to the A4 but can be cheap to run, As a side note the more i save the more pennies i have to finish my mini and stop writing posts about how expensive running a car is. ;D ;D ;D

[oxb1l]

I ran a mk4 golf tdi and got about 47 to the gallon
I needed a bigger car so went for a Passat (same engine) it's more expensive to tax
My misses won't drive it and it averages 37 to the gallon

I just use the car less

Bill

[ben711200]

It's really worth figuring out for individual cars if you know their fuel consumption. I think I figured out recently that the cost difference between diesel and petrol worked out at about 5mpg (ie, my derv Passat does 50mpg, a petrol car that does 45mpg would have the same fuel cost).

At the moment, I drive a 1.9td Passat that I can quite happily chuck veg in, and my partner drives a 1.4tdi Polo that on the last tank did 53mpg. I wasn't going slowly either because it's quite an entertaining drive...

As to which is 'better'. Surely that depends on mileage, personal taste, driving style.... For me, diesel wins every time. But I do lots of motorway and A road miles and need a bigger car for hauling the baby (small people have masses of stuff and seats that are too big for little cars).

[damien4884]

Quite a few years back I had a 1.7 diesel astra followed closely by a 1.6 16v astra. Had a running joke with the diesel, as I didn't have a particularly good job, that for every 10 miles I wanted to travel it would cost me £1 in fuel, IIRC diesel was £1.17ish a litre. my weekly commute was 100 miles a week, so £10 in fuel (my dad had it after me and he kept to same principal even to the point of ignoring the fuel light coming on) The petrol one however was nearer £25 a week for same distance. I find with diesels once your are up to speed it takes very little throttle to keep it there, even with our 04 meriva, (which btw gets 400-450 miles to a tank and I have never put more than £55 in to fill it up and most of the time it isn't even warm by the time I get to work) takes very little foot pressure to sit at 70. Whereas the petrol felt like you were hooning it everywhere.

PS the meriva is a 1.7 cdti and gets better fuel consumption than the father in laws 1.3 cdti combi van of same age and he drives like miss daisy!

[lordyoung1980]

I'm convinced this Audi has a problem somewhere, its gutless when i leave work i have to leave my radio at the gate house and the guard always comments that when i drive off site it reeks of petrol. Also the temp guage does not move much. Theres no EML on the dash but thats not always meaning its ok. I think its looking more like the diesel way again for me.

[damien4884]

Going by my rough guess, £50 at 1.46/l = 34.25 ish litres of fuel which is a tad over 7.5 gallons 150 mile round trip (approx-using google maps) means your getting 20mpg. Quick google gives your car as:

24.5 urban
42.8 extra urban
33.6 combined

[Harold Ramp Bumface Fandango]

I've got a one litre Corsa and I reckon that's cheaper to run than my Audi 80 TDi.

[ben711200]

The other thing to consider is that it can't really be a fair comparison unless it's like for like. My B4 Passat td gets 45-50mpg depending on how/where I drive. I can't imagine any of the petrol B4s get better than high 30s on a run. A 1 litre petrol corsa/matiz/generic modern compact will get similar mpg so be cheaper to run but I would be utterly lost without the biggish estate.

[lordyoung1980]

Apr 13, 2012 20:57:36 GMT damien4884 said:

Going by my rough guess, £50 at 1.46/l = 34.25 ish litres of fuel which is a tad over 7.5 gallons 150 mile round trip (approx-using google maps) means your getting 20mpg. Quick google gives your car as:

24.5 urban
42.8 extra urban
33.6 combined

Oh dear

[RobinJI]

Apr 13, 2012 19:15:57 GMT oxb1l said:

I ran a mk4 golf tdi and got about 47 to the gallon
I needed a bigger car so went for a Passat (same engine) it's more expensive to tax
My misses won't drive it and it averages 37 to the gallon

I just use the car less

Bill

I fear your Passat's either broken or you're thrashing the nads off it everywhere. You really shouldn't be getting that low figures. Any model of 1.9tdi Passat should manage 50mpg unless you've got a lead foot or live in central london.


If you want better fuel consumption, then in a like for like car, there's little arguing that a diesel will be better. They're just more efficient engines for normal road use. That's not to say they're better though, because what makes and engine 'better' is, as Ben says, subjective.

This was the view of my 1.6td B3 Passat's dash last night on my way home from uni. The trip-counter was reset when I brimmed the tank .



I'll expect ~900 miles to that 70 litres of fuel, which works out at 58mpg, in a full sized estate car. 200 miles of that was done in hilly South Somerset back roads, 100 miles on a very congested A303 (4 hours to do a 2.5 hour trip) and the other 200 at ~70 on various dual carriageways. If like Ben says, the cost difference equates to 5mpg difference, then you'd need to manage 53mpg from a petrol equivalent, which in my experience, would not be even close to possible in the same conditions, you'd be looking at closer to 40 on a good day. Then bare in mind this engine had zero electronics, it's a fully mechanical engine dreamt up in the early 1980's, and a technologically equivalent petrol engine would be lucky to break 35.

[Lawsy]

I think the newer diesels arent as effiecient as their older counterparts..

I;ve had diesel passats, B3 through B6.. the B3 was th ebest, as robin shows, easily got 60 mpg - same engine in mk2 goof GTD was getting about the same, but driven harder, i had amk3 goof estate witht he 1.9TDI and a B4 1.9 passat with the 1Z TDI - the goof got around 55mpg and the B4 about 52 so not a lot in it
I had a B5.5 with the 1.9 TDI and that would do high 40's averaging about 47-48
then I've just got rid of my much newer 2.0 TDI B6 passat, ok it was the most powerful, but would struggle to average more than 40mpg ona tank full - thats proper brim the tank and work it out from 4.54 litrs to a gallon etc...

Whereas I see petrols getting better, some one i know has a 1.4 golf and is getting mid 40's where as a 1.4 golf from 15/20 years ago would have got 30-35

So i guess the answer lies as shown, age of vehicle, spec, size all comes to play when considering the mpg's and comparison

[jrevillug]

Apr 13, 2012 20:22:44 GMT lordyoung1980 said:

I'm convinced this Audi has a problem somewhere

Definitely.

My Dad has a 1996 Audi A6 with the 1.8 20v non-turbo - so the same engine as yours, but in a bigger car. It returns ~35mpg on my Dad's 60-mile round trip commute (mixed A roads and motorways), and a touch over 40 on a run.

I recently drove it to Coventry and back - a round trip of ~145 miles. When I left home, the fuel gauge was reading around a quarter. In Coventry I put £40 in (at 139.9p/L), and when I got home the fuel gauge was reading just under half a tank. I don't think the entire journey cost much more than £20 in petrol.

Admittedly, that was a gentle run up the motorway (~70 where the traffic was free, slower if not) - whereas your run was on A-roads - but there's a huge disparity in fuel consumption there.

A few thoughts in no particular order:

-Airflow meter?

-Lambda sensor? When the lambda went on my friend's Micra the fuel consumption increased massively.

-Camshaft timing:

I recently helped my Dad replace the timing belt on his Audi, and found that the timing had been set improperly by the last garage to do so - the camshaft timing was retarded by one tooth on the cam pulley. Re-setting the timing to the correct position a) massively improved the low-end torque and b) improved the fuel consumption on the commute by about 4mpg. (BTW - even with the timing out I squeezed 40mpg out of it on a long (~500 mile) gentle run, so this is probably not the only problem.)

Taking the top belt cover off to check the cam timing shouldn't be too tricky.

-Thermostat:

My Dad's Audi has a stuck thermostat, which means that it runs cool, and the temp gauge doesn't move much. He's currently running round with a bit of plastic stuffed in front of the radiator, which helps it run a bit warmer, improves the heater no end, and has improved the economy - although by how much I don't know - and is planning to swap the thermostat soon.

How effective is the heater on yours? If it's a bit curse word then change the thermostat ASAP.

-Finally - coilpacks. There are 2 on these engines - one over each of the rearmost spark plugs, with the front plugs connected by short plug leads. If one pack had failed, the engine would be hugely down on power, and all the fuel chucked into the dead cylinders would go straight out of the exhaust without being burnt. This would kill the cat quickly by over-heating it.

EDIT: reading this list back, I'd start by checking for a spark on both front plugs, then get the lambda checked, then change the 'stat, and check the cam timing and airflow meter last of all. If you can get it onto a proper VAG diagnostics setup you'll probably be able to find out what's wrong pretty quickly.

Hope this helps.
James

EDIT2: to add that all the mpg figures in this post are calculated using petrol pump litres and recorded mileage - the Audi's pretty much base-spec, so lacks a trip computer.

[Harold Ramp Bumface Fandango]

Apr 13, 2012 21:45:42 GMT ben711200 said:

The other thing to consider is that it can't really be a fair comparison unless it's like for like. My B4 Passat td gets 45-50mpg depending on how/where I drive. I can't imagine any of the petrol B4s get better than high 30s on a run. A 1 litre petrol corsa/matiz/generic modern compact will get similar mpg so be cheaper to run but I would be utterly lost without the biggish estate.

Absolutely, can't argue with that and it's probably why petrol versions of diesel cars (if that makes sense!) are cheaper and less desirable.

[fray-bentos-uk]

Have you considered the LPG route? i made that choice about 18 months ago, best decision i ever made. Some people will scare monger about blown engines etc., but my personal experience is if you look after things properly, they are reliable.

[undernutter]

Worth bearing in mind the kind of mileage/journeys you do.

Any engine will drink more before its up to temperature, but AFAIK, diesels more so, they need to be driven for longer before they reach peak efficiency. So a DERV isnt nescasserily a good idea if you do a lot of short journeys.

My daily hack is the peugeot in my sig, a 1.1 carb. I average 350 miles to a tank out of that, mixed driving, and its about £50-£55 to fill it up. Just taken it down to the new forest and back, loaded with four, luggage, and a box trailer.
Brimmed the tank before we left for home and now I'm on the 3/4 mark on the gauge.

[lordyoung1980]

Apr 14, 2012 15:43:21 GMT jrevillug said:

Apr 13, 2012 20:22:44 GMT lordyoung1980 said:

I'm convinced this Audi has a problem somewhere

Definitely.

My Dad has a 1996 Audi A6 with the 1.8 20v non-turbo - so the same engine as yours, but in a bigger car. It returns ~35mpg on my Dad's 60-mile round trip commute (mixed A roads and motorways), and a touch over 40 on a run.

I recently drove it to Coventry and back - a round trip of ~145 miles. When I left home, the fuel gauge was reading around a quarter. In Coventry I put £40 in (at 139.9p/L), and when I got home the fuel gauge was reading just under half a tank. I don't think the entire journey cost much more than £20 in petrol.

Admittedly, that was a gentle run up the motorway (~70 where the traffic was free, slower if not) - whereas your run was on A-roads - but there's a huge disparity in fuel consumption there.

A few thoughts in no particular order:

-Airflow meter?

-Lambda sensor? When the lambda went on my friend's Micra the fuel consumption increased massively.

-Camshaft timing:

I recently helped my Dad replace the timing belt on his Audi, and found that the timing had been set improperly by the last garage to do so - the camshaft timing was retarded by one tooth on the cam pulley. Re-setting the timing to the correct position a) massively improved the low-end torque and b) improved the fuel consumption on the commute by about 4mpg. (BTW - even with the timing out I squeezed 40mpg out of it on a long (~500 mile) gentle run, so this is probably not the only problem.)

Taking the top belt cover off to check the cam timing shouldn't be too tricky.

-Thermostat:

My Dad's Audi has a stuck thermostat, which means that it runs cool, and the temp gauge doesn't move much. He's currently running round with a bit of plastic stuffed in front of the radiator, which helps it run a bit warmer, improves the heater no end, and has improved the economy - although by how much I don't know - and is planning to swap the thermostat soon.

How effective is the heater on yours? If it's a bit curse word then change the thermostat ASAP.

-Finally - coilpacks. There are 2 on these engines - one over each of the rearmost spark plugs, with the front plugs connected by short plug leads. If one pack had failed, the engine would be hugely down on power, and all the fuel chucked into the dead cylinders would go straight out of the exhaust without being burnt. This would kill the cat quickly by over-heating it.

EDIT: reading this list back, I'd start by checking for a spark on both front plugs, then get the lambda checked, then change the 'stat, and check the cam timing and airflow meter last of all. If you can get it onto a proper VAG diagnostics setup you'll probably be able to find out what's wrong pretty quickly.

Hope this helps.
James

EDIT2: to add that all the mpg figures in this post are calculated using petrol pump litres and recorded mileage - the Audi's pretty much base-spec, so lacks a trip computer.

I blanked the grill off during the cold months, only took it off 2 weeks ago. Air flow meter failed the day i got it, so thats new. . The heater is not cold but could be better so i'm with you on the thermostat. I replaced the plugs and filter when i took the cover off the grill and the coil packs are fine. I'm going to look for the thermostat in the morning,if i can find it. I've had to change or repair loads of breather pipes since i've had it and i've probably still got loads more to change . its only got 2 more months left till the MOT is up, so i'll do what i can but i hearts not in it.

[MK2VR6]

Good thread idea. My daily is a 2003 Audi a4 avant tdi 130. However, most of my journeys are now very short for the next 6 months or so, and I'm toying with the idea of a Peugeot 106 diesel or petrol as they are so frugal, and sorning the Audi until the situation changes. I'm now wondering if the petrol 106 will be better for short journeys?

[akku]

I don't do diesels. I drive petrol cars. Yes, they use more fuel but, meh. I drive what I like.

My ex-wife is selling her turbo Saab convertible to get a Micra or some such because of the Saab's high fuel consumption. But she does 30-40 miles a week! She could run a Rolls Royce or an Escalade and the actual extra fuel cost would be negligible.

If you are doing 100 miles a day or something then you probably need to be looking for every mile per gallon.

I'd rather drive less and do so in a car I liked.

[loudandproud205]

Apr 14, 2012 20:36:13 GMT MK2VR6 said:

Good thread idea. My daily is a 2003 Audi a4 avant tdi 130. However, most of my journeys are now very short for the next 6 months or so, and I'm toying with the idea of a Peugeot 106 diesel or petrol as they are so frugal, and sorning the Audi until the situation changes. I'm now wondering if the petrol 106 will be better for short journeys?

Go for a Saxo VTR nice trim level and still some performance and quite good mpg.

Other wise I'd stick with the diesel idea, they don't mind short journeys mine was happy enough with it and did great MPG say that I used to get 40ish MPG out of my VTS when driven with respect.

[Dez]

Apr 14, 2012 17:42:22 GMT undernutter said:

Worth bearing in mind the kind of mileage/journeys you do.

Any engine will drink more before its up to temperature, but AFAIK, diesels more so, they need to be driven for longer before they reach peak efficiency. So a DERV isnt nescasserily a good idea if you do a lot of short journeys.

this is very true. we have a 2.0 petrol b3 passat(mk3 fgti 8v engine), and a lupo tdi sport, 1.4 diesel.
for a journey under about 3 miles, they do the same mpg, 15-20 ish, even though the pupo is half the size.
as soon as you get over that the diesel starts using massively less fuel compared to the petrol as it warms up, with the petrol averaging 35-40mpg, and the diesel 65-70.