Thirsty V6 Xantia

[Mandrake]

I have just done a 580km trip ( approx 50/50 urban / freeway ) & used 55 liters of 98 with, lets say,the occasional enthusiastic driving ( one can not be gentle with a v6 accelerator , it is just not possible to a normal male!) .

By my calculation that's 29MPG or 10.5km/litre which is far better than the 19.8MPG I got with a similar 50/50 urban/motorway mix

It is the first trip since having the steering toes set to 7mm & I believe the car is tracking & running very well , riding & handling like a dream but filling the tank at the end of the day & handing over $100 was a pain. My VSX gets 600k from 55l all urban driving on part ethanol.

Again by my calculation thats 30.8MPG, or 10.9km/litre, quite remarkable for urban driving. Is that an auto or manual ? On my 2 litre auto the best I could ever get on urban only was about 23MPG, 28MPG on 50/50 urban/motorway and about 32MPG motorway only...

So your V6 appears to be getting better mileage than my 2 litre auto did!

[Ozzie Kuma]

both auto.. I have "loved" the VSX from new.. so it is comforting to still be getting good economy,.. I just do not want to part with it but it is near its used by date / milage so it will come soon.

[addo]

Mandrake: Road surface roughness can play a part, however the principal cause of your car's thirst is, IMO, utterly worn out lower arm bushings.

You cannot test these effectively with a prybar. Giveaway signs are heavy fuel usage, scuffing across the tyre surface (as opposed to balljoints, which usually cause inner edge wear), excessive wheelspin on takeoff or hard acceleration from a rolling start. Tyre squeal when cornering hard can also be a clue. Assuming the struts are still OK, then a new set of bushes will fix it all nicely.

[Mandrake]

Mandrake: Road surface roughness can play a part, however the principal cause of your car's thirst is, IMO, utterly worn out lower arm bushings.

At 97,000 miles ?

[addo]

Absolutely - it's not an XF Falcon! I reckon the service life of lower suspension elements in PSA cars of the later '90s is 80-120K (km), depending on usage.

I killed the first set by 140K kilometres, and the replacement Sasic bushes are utterly rooted at 220K (albeit with much heavy towing). I realigned it once for a cheap fix, but the degradation has caught up again. Going to fit TRW bushes this time, as I believe ZF-Lemförder are now largely trading on past reputation.

[lexi]

Hi Mandrake:
Only ever used the super duper Shell fuel in the v6's. I never checked your V6 for fuel consumption as did not use it much.

It did not seem any worse than the mark 1 though. I thought I was getting 30 on a run with that but who knows when you aint brimming and testing.

The tyres on your car just seemed to be budget that had been on too long for their own good...hence cracking maybe?

[Mandrake]

Hi Mandrake:
Only ever used the super duper Shell fuel in the v6's. I never checked your V6 for fuel consumption as did not use it much.

Was that Shell 95, or 98 ?

I'm thinking of trying it on some BP Ultimate 98 next time, as there is one just up the road. I'll let it run right down into the warning zone first to minimize the mixing of the two...

It did not seem any worse than the mark 1 though. I thought I was getting 30 on a run with that but who knows when you aint brimming and testing.

I've only done the one accurate fill and measure so far, so I'll see what I get next time.

The tyres on your car just seemed to be budget that had been on too long for their own good...hence cracking maybe?

Yeah they look like tyres that have been sitting on a low mileage car for a long time.... They seem to be sagging even more in the sidewalls now than before - I've got 34psi in them but they look like they've got about 30 in them, and the steering seems quite a bit heavier than I remember it being at first. My guess is they're on the way out, and quickly... I think I've done close to 800-1000 miles now

Would love to put a good pair of Michelins on, (made a massive difference to ride and handling on my last Xantia) will have to do some homework on what to get, hopefully I can afford some in May or June.

[Mandrake]

Absolutely - it's not an XF Falcon! I reckon the service life of lower suspension elements in PSA cars of the later '90s is 80-120K (km), depending on usage.

I killed the first set by 140K kilometres, and the replacement Sasic bushes are utterly rooted at 220K (albeit with much heavy towing). I realigned it once for a cheap fix, but the degradation has caught up again. Going to fit TRW bushes this time, as I believe ZF-Lemförder are now largely trading on past reputation.

You've certainly made a good point about worn lower arm bushes as a possible cause of high tyre wear/low MPG, (hadn't really thought of it before) but I'm not convinced that its an open and shut case just because the car has done 97,000 miles...(~150,000Km)

My previous Xantia (in NZ) had done 139,000Km when I got it, and 180,000Km when I sold it, I never touched the arm bushes, could tell they were originals, wheel tracking was good, no problems with low MPG, the same tyres (Michelin XM1) were on for over 35,000Km with no signs of scuffing or unusual wear.

Another Xantia of ours (a 1.9TD) had done 220,000Km when it was first bought and its still going, seemingly on the original bushes as well, and it does normal MPG for the model and doesn't scuff the tyres.

Another factor is that heat and humidity (as found in many parts of AUS) accelerates the breakdown of rubber bushes (including strut top rubbers) - heat and humidity are not a problem in the UK where it's cold and dry...strut top rubbers don't fail prematurely here, so I suspect other rubber components don't either. (Rust on the other hand.... )

Replacing the arm bushes is not a job I really want to tackle at the moment, before I would attempt that I have 3 obvious things to do (1) completely knackered front tyres with cracked bulgy sidewalls that need replacing (2) front wheel alignment hasn't been checked yet, (3) brake drag is a real potential problem, front brakes and handbrake haven't been checked yet, rear callipers are badly out of alignment with the disc due to rust and quite likely there is some drag or binding occurring despite the patch up job I did until I can fix the calliper alignment properly.

If I do all of those and still have MPG problems, then I'll take a look at the arm bushes...

[Mandrake]

Ok chaps, an update on the MPG situation. I seem to be getting a consistent 20MPG +/- 1MPG pretty much regardless of the balance between urban and motorway driving...

What I have discovered is a completely knackered right hand outer track rod joint. I can wobble the slack by turning the hub very easily and although I haven't measured it I would say visually the slack is at LEAST 1mm, possibly as much as 2mm, my question is, is this amount of slack in a track rod joint enough to cause enough wheel tracking issue that would explain such a low MPG ?

If I have 1mm of slack at the track rod end, by the time we get to the edge of the wheel thats a potential error of 2mm in total, 1mm each way, does that mean the total toe in is potentially varying as much as 4mm under loads ? (Or more if the slack is more than 1mm...) I have to admit I can't remember where toe in (in millimetres, not degrees) is measured, I was under the impression that you measure the distance in length between the left and right tyre both at the front edge of the tyre bead (half way between rim and tread) and the rear edge and take the difference ?

I also sometimes notice a "shudder" if I accelerate quickly from a standstill on a right hand corner which I'm now thinking could be due to the track rod slack vibrating with the torque, and wonder if it is also the cause of the vibration I notice at 70-80mph which comes and goes.

In a cursory glance I wasn't able to find any other joints with slack, although it sounds like there is some slack somewhere on the left hand side, possibly a lower balljoint judging by the sound. (Without uncoupling the lower arm I can't prove it though)