xjr v8 oil consumption
Discussion
What viscosity oil are you using? I put in a winter-spec 5W-40 or 0W-40 last year, and it disappeared as soon as spring hit and ambient temperatures rose. Standard 10W-40 is fine though.
Otherwise, the oil is going out somewhere, either through the valve stems or the exhaust.
Is it producing smoke from the exhaust? If not, it may be the valve stems. Not generally considered to be a good thing either way.
Otherwise, the oil is going out somewhere, either through the valve stems or the exhaust.
Is it producing smoke from the exhaust? If not, it may be the valve stems. Not generally considered to be a good thing either way.
Dont forget every engine is very slightly different, Engine manufactureers use a set of tolerances and anything upto 1 litre per 1000 miles is acceptable to them.
In general cars dont burn much, but i once had a toyota that burnt almost a litre every 1000 miles.
Dont even get me started on the RX8, I beleive they can drink a litre at every fuel fill up !!
In general cars dont burn much, but i once had a toyota that burnt almost a litre every 1000 miles.
Dont even get me started on the RX8, I beleive they can drink a litre at every fuel fill up !!
alanmercer7 said:
Hi, Thanks for that. Do you have a photo to show me where the breather pipe is.
The part throttle breather is one of two breather pipes on the top inside edge of the cam covers. Inside the male flange that the part throttle breather pipe fits over on the LH cover is a calibrated 2.5mm diameter hole. On earlier AJ26 engines it's well worth cleaning out the hole, using some carb cleaner and a 2.5mm drill bit and making sure that the full load breather on the RH side is not blocked. Cleaning out the inside of the throttle body and butterfly too using more carb cleaner and a soft cloth or toothbrush is a good idea too whilst you've got the bonnet open.You should have a slight vacuum on the full load breather flange with a heathy engine and clear breather system whilst at idle.
One other thing worth considering is the quality of oil you've used. Ordinary mineral oils have their hot viscosity boosted by long chain polymers - that's how you get a multiviscosity oil like a 10W - 40 spec. The 10(W) is the base specification oils viscosity at low temperature and it's stopped from thinning quite so much as it would otherwise do at high temperatures by the addition of polymer chains, that's where the 40 comes from.
As the oil ages the polymer chains break down causing the origional 10-40 to become a 10-35 and then a 10-30 and so on. Lower hot viscosity also means a thinner oil film which means a worm, but nowhere near knackered engine - especially one that's boosted and driven hard - will use quite a lot of oil once the hot viscosity falls away without leaving the sort of smokescreen 007 would be pleased with behind you. Oil change to a good full synthetic which holds its hot viscosity through the life of the oil fill will make a huge difference to the rate of oil consumption on a slightly worn engine.
Edited by Jaguar steve on Saturday 19th June 22:15
Hi Steve, The breather pipe described below,is it left of the oil filler cap with a small plastic safety clip attached, if so how do you get the pipe off-pull or twist? ------------------------------- The part throttle breather is one of two breather pipes on the top inside edge of the cam covers. Inside the male flange that the part throttle breather pipe fits over on the LH cover is a calibrated 2.5mm diameter hole. On earlier AJ26 engines it's well worth cleaning out the hole, using some carb cleaner and a 2.5mm drill bit and making sure that the full load breather on the RH side is not blocked
The full load breather is on the opposite cam cover - no calibrated hole this time it's just a pipe. Chances are if that's blocked you have a very dirty engine indeed. Check the air filter is clean.
The throttle body is at the rear of the engine in the centre of the V. Take off the large black plastic air pipe that feeds the body from the air filter box and look inside the throttle body. You'll see a brass coloured butterfly valve inside a silver coloured tube.
Spray inside with carb cleaner and wipe off until the visible parts are clean. Then very gently open the butterfly with your finger, hold it open and spray more carb cleaner down the tube. Use an old toothbrush and more carb cleaner to clean down past the valve.
Being a tad clumsy here is bad news so FFS don't either risk dropping anything past the valve or use any sharp tools which may scratch the valve or tube insides. Last time I looked a new throttle body from Jaguar was a lot of money...
The throttle body is at the rear of the engine in the centre of the V. Take off the large black plastic air pipe that feeds the body from the air filter box and look inside the throttle body. You'll see a brass coloured butterfly valve inside a silver coloured tube.
Spray inside with carb cleaner and wipe off until the visible parts are clean. Then very gently open the butterfly with your finger, hold it open and spray more carb cleaner down the tube. Use an old toothbrush and more carb cleaner to clean down past the valve.
Being a tad clumsy here is bad news so FFS don't either risk dropping anything past the valve or use any sharp tools which may scratch the valve or tube insides. Last time I looked a new throttle body from Jaguar was a lot of money...
Thanks, I have the checked the other breather ( fairly clean), and have changed the oil to 10w40 and also new filter,so will see how that goes before tackling the next stage. The other mystery,is that compared to my last xjr (1998) with 155000 miles on the clock, and a regular average around the 20mpg mark, this one seems to average around 16ish -any suggestions. Cheers Alan
Edited by alanmercer7 on Thursday 1st July 18:31
First you need to check you really do have the difference in consumption between the two cars - and the only way to do that is with several brim to brim fills and 5 mins with a calculator.
Are your driving pattens the same? I once had a customer who complined repeatedly about the replacement car's fuel consumption he'd bought from us compared to his identical model previous one.
Both myself and my Foreman managed an easy 55MPG on extended road testing yet he was seeing no better than low to mid 30's. Turned out he'd moved home at the same time as he'd changed the car and his new commute to work involved a 100 yard drive from his house to the nearest motorway and then he'd boot it up to 80MPH or so from stone cold. The only way to keep the wretched 1100cc Eurobox going at that speed in the sub zero temperatures we had at the time was to mash the throttle into the carpet and leave the choke half out for the first few miles 'till the engine warmed up...
First things to do if you really do have a excessive fuel consumption would be clean out the throttle body and check the air filter is clean, jack up each corner and see if the wheels turn freely - if not you may have a binding brake or sezied handbrake cable or some resistance in the driveline or diff somewhere. Make sure the tyres are evenly worn - that's a good rough check the suspension geometry is not miles out leading to extra rolling resistance - and the pressures are correct. None of these will be likley on it's own to cause a big difference but all the little things add up. After a drive have a walk round and feel the wheels to see if any one is significantly hotter than the rest.
It's financially worth a change to a fully synthetic oil too, just a 1 or 2% improvement in fuel consumption due to reducing engine friction and better bottom end temperature control will more than pay for the slight extra cost of the oil over the sumpfill lifetime and you'll have massively better engine protection too. Check your handbook but I'm pretty sure you can use a 5W-30 in an XJR
If you can't see anything obviously wrong with the oily bits then a diagnostic scan at a Jaguar indy would be a few quid well spent.
Are your driving pattens the same? I once had a customer who complined repeatedly about the replacement car's fuel consumption he'd bought from us compared to his identical model previous one.
Both myself and my Foreman managed an easy 55MPG on extended road testing yet he was seeing no better than low to mid 30's. Turned out he'd moved home at the same time as he'd changed the car and his new commute to work involved a 100 yard drive from his house to the nearest motorway and then he'd boot it up to 80MPH or so from stone cold. The only way to keep the wretched 1100cc Eurobox going at that speed in the sub zero temperatures we had at the time was to mash the throttle into the carpet and leave the choke half out for the first few miles 'till the engine warmed up...
First things to do if you really do have a excessive fuel consumption would be clean out the throttle body and check the air filter is clean, jack up each corner and see if the wheels turn freely - if not you may have a binding brake or sezied handbrake cable or some resistance in the driveline or diff somewhere. Make sure the tyres are evenly worn - that's a good rough check the suspension geometry is not miles out leading to extra rolling resistance - and the pressures are correct. None of these will be likley on it's own to cause a big difference but all the little things add up. After a drive have a walk round and feel the wheels to see if any one is significantly hotter than the rest.
It's financially worth a change to a fully synthetic oil too, just a 1 or 2% improvement in fuel consumption due to reducing engine friction and better bottom end temperature control will more than pay for the slight extra cost of the oil over the sumpfill lifetime and you'll have massively better engine protection too. Check your handbook but I'm pretty sure you can use a 5W-30 in an XJR
If you can't see anything obviously wrong with the oily bits then a diagnostic scan at a Jaguar indy would be a few quid well spent.
I have to-day had the tracking checked -2mm out- and as I said before had the oil changed to 10w 40 which was recommended by my jag guy. The wheels seem to turn freely. I am a bit nervous of tackling the throttle body, but will give it a go. You are maybe right with the variations on my routes,but 2-3mpg seems a lot when your only getting 16ish. Anyway thanks again for your help
Cleaned out the throttle body, didn't look too bad, but the airpipe down at the filter end was dripping oily stuff -cleaned it out and the performance seems to have improved, but not the mpg, checked the wheels and all were the same temperature. Maybe I am just driving differently because its a new car,and looking for better performance,resulting in poorer mpg.
alanmercer7 said:
Cleaned out the throttle body, didn't look too bad, but the airpipe down at the filter end was dripping oily stuff -cleaned it out and the performance seems to have improved, but not the mpg, checked the wheels and all were the same temperature. Maybe I am just driving differently because its a new car,and looking for better performance,resulting in poorer mpg.
Happens to the best of us 
- that's 'till you get the credit card bill and add up just how much you've spent on petrol in the last month 
That's when you start driving like a real Pussy and pretty soon learn how to nurse an XJ8 up to 29MPG on a long trip.
Gassing Station | Jaguar | Top of Page | What's New | My Stuff